JP2006069852A - Method for manufacturing carbon-doped silicon single crystal and carbon-doped silicon single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a carbon-doped silicon single crystal by which carbon can be easily doped in a silicon single crystal with high accuracy and the carbon-doped silicon single crystal can be manufactured at a low cost. <P>SOLUTION: In the method for manufacturing a silicon single crystal by a Czochralski method while doping carbon, the method for manufacturing the carbon-doped silicon single crystal is characterized by including at least a process for preparing carbon fibers and/or silicon carbide fibers as a dopant, a process for filling the dopant comprising the carbon fibers and/or silicon carbide fibers together with silicon polycrystal provided as a raw material into a crucible, a process for melting the filled raw material into a raw material melt, and a process for growing a carbon-doped silicon single crystal rod from the raw material melt. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a silicon single crystal for cutting a silicon wafer used as a substrate for a semiconductor device such as a memory or a CPU. In particular, the present invention relates to crystal defects and impurity gettering by doping carbon used in the most advanced fields. The present invention relates to a method for producing a silicon single crystal with a controlled BMD density and a silicon single crystal.

  Silicon single crystals for cutting out silicon wafers used as substrates for semiconductor devices such as memories and CPUs are mainly manufactured by the Czochralski method (hereinafter abbreviated as CZ method).

  The silicon single crystal produced by the CZ method contains oxygen atoms. When a device is manufactured using a silicon wafer cut out from the silicon single crystal, the silicon atoms and oxygen atoms are combined to form oxygen precipitates ( Bulk Micro Defect (hereinafter abbreviated as BMD) is formed. This BMD is known to have an IG (Intrinsic Gettering) ability to capture contaminant atoms such as heavy metals inside the wafer and improve device characteristics, and obtain a higher performance device as the BMD density in the bulk portion of the wafer increases. be able to.

  In recent years, in order to provide sufficient IG capability while controlling crystal defects in a silicon wafer, a silicon single crystal is manufactured by intentionally doping carbon or nitrogen.

  Regarding the method of doping carbon into a silicon single crystal, a method using gas dope (see Patent Document 1), a method using high-purity carbon powder as a dopant (see Patent Document 2), and a carbon lump (block-like carbon as a dopant) ) (See Patent Document 3) and the like have been proposed. However, in the method using gas dope, when the crystal is disturbed and remelted, it is difficult to control the carbon concentration. In the method using high purity carbon powder, the high purity carbon powder is scattered by the introduced gas when the raw material is melted. In the method using lumps, there is a problem that carbon is difficult to dissolve, and it takes time to dissolve the carbon lumps, and crystals being grown are likely to be disturbed.

Here, as one method for producing a single crystal by the CZ method, a method for producing a plurality of silicon single crystals in one batch, a so-called multi-pooling method is known (see Non-Patent Document 1). In this method, after pulling up a single crystal having a dopant concentration in a range satisfying the resistance standard, a raw material corresponding to the pulled weight is additionally charged, and the same single crystal is pulled again. In the multi-pooling method, since a plurality of single crystals are produced from a quartz crucible that can be used only once, the production yield can be improved and the cost for preparing the quartz crucible can be reduced.
Even in such a multi-pooling method, as a method for doping carbon, a method using gas dope, a method using high-purity carbon powder, and a method using a carbon lump are adopted. Therefore, it is difficult to control the carbon concentration when the crystal is disturbed and remelted by the method using gas dope. In the method using high purity carbon powder, the high purity carbon powder is scattered by the introduced gas or the like when the raw material is melted. In the method using lumps, there is a problem similar to that described above, in which carbon is difficult to dissolve and it takes time to dissolve the carbon lumps, and the crystals being grown are likely to be disturbed.

  As means for solving these problems, in Patent Document 4, as a method for doping carbon into a silicon single crystal, a silicon polycrystalline container containing carbon powder, a silicon wafer formed by vapor deposition of carbon, and an organic containing carbon particles There has been proposed a method in which a silicon wafer coated with a solvent and baked, or a silicon polycrystal containing a predetermined amount of carbon is introduced into a crucible. If these methods are used, the above-mentioned problems can be solved. However, all of these methods require processing of polycrystalline silicon, heat treatment of the wafer, etc., and it is not easy to prepare a carbon dopant. Furthermore, there is a possibility of contamination by impurities during processing for adjusting the dopant and heat treatment of the wafer. In addition, when using a silicon wafer that has been coated and baked with an organic solvent containing carbon particles as the carbon dopant, the organic solvent itself often does not satisfy the impurity concentration in the semiconductor grade, and the crystals pulled up from it are contaminated. There was a problem.

In addition, a method has been proposed in which carbon and nitrogen are simultaneously doped to obtain a silicon single crystal with few grown-in defects and high IG ability (see, for example, Patent Document 5 and Patent Document 6). As a method for doping nitrogen into a silicon single crystal, a method in which a wafer having a silicon nitride film formed on the surface is introduced into a polycrystalline raw material (see, for example, Patent Document 7) is generally used.
However, even in these methods of doping both nitrogen and carbon, as a carbon doping method, a method using gas dope, a method using high-purity carbon powder, a method using carbon lump, and the like are adopted. Therefore, it is difficult to control the carbon concentration when the crystal is disturbed and re-melted by the method using gas dope. In the method using high-purity carbon powder, the high-purity carbon powder is scattered by the introduced gas when the raw material is melted. In the method using lumps, there are the same problems as described above, such that carbon is difficult to dissolve, and it takes time to dissolve the carbon lumps, and crystals being grown are likely to be disturbed.

JP 11-302099 A JP 2002-293691 A JP 2003-146696 A Japanese Patent Laid-Open No. 11-312683 JP 2001-199794 A International Publication No. 01/79593 JP-A-5-294780 (Semiconductor Silicon Crystal Technology, Fumio Shimura, p178-p179, 1989)

  The present invention has been made in view of such problems, and it is possible to dope carbon into a silicon single crystal easily and with high accuracy, and to produce a carbon-doped silicon single crystal at a low cost. It aims at providing the manufacturing method of a crystal | crystallization.

  The present invention has been made to solve the above problems, and in the method for producing a silicon single crystal by doping carbon by the Czochralski method, at least carbon fibers and / or silicon carbide fibers are prepared as a dopant. A step of filling the crucible with a dopant composed of the carbon fiber and / or silicon carbide fiber together with silicon polycrystal prepared as a raw material, a step of melting the filled raw material into a raw material melt, A method for producing a carbon-doped silicon single crystal, comprising the step of growing a carbon-doped silicon single crystal rod from the raw material melt.

  Carbon fiber and silicon carbide fiber are inexpensive and easily available in high purity. In addition, carbon fibers and silicon carbide fibers are less likely to scatter like powders, have a large surface area, and are much easier to dissolve than carbon blocks. In addition, the carbon dope concentration can be adjusted more easily than when gas is used. In the present invention, such a carbon fiber and / or silicon carbide fiber is used as a dopant to produce a carbon-doped silicon single crystal. Therefore, carbon can be easily doped into the silicon single crystal with high accuracy, and the carbon-doped silicon single crystal can be manufactured at low cost.

  Further, the present invention provides a method for producing a silicon single crystal by doping carbon by the Czochralski method, at least a step of growing a silicon single crystal rod from an initial raw material melt contained in a crucible, and the growth A step of taking out a silicon single crystal rod, a step of preparing carbon fibers and / or silicon carbide fibers as a dopant, a silicon polycrystal prepared as an additional raw material, and a dopant comprising the carbon fibers and / or silicon carbide fibers as a crucible A method for producing a carbon-doped silicon single crystal, the method comprising: filling the inside, melting the additional raw material, and growing a carbon-doped silicon single crystal rod from the added raw material melt (Claim 2).

That is, after the first silicon single crystal rod is grown from the initial raw material melt, the carbon-doped silicon single crystal rod is grown as the second single crystal rod. The present invention uses carbon fiber and / or silicon carbide fiber as a dopant when growing the second single crystal rod. Therefore, carbon can be easily doped into a silicon single crystal rod with high accuracy, and a carbon-doped silicon single crystal can be manufactured at low cost.
Note that the first silicon single crystal rod grown from the initial raw material melt may be a carbon-doped silicon single crystal or a silicon single crystal not doped with carbon.

  In this case, two or more carbon-doped silicon single crystal rods can be grown by repeating from the step of taking out the single crystal to the step of growing the carbon-doped silicon single crystal rod. Item 3).

  As described above, by growing two or more carbon-doped silicon single crystal rods by the multi-pooling method, it is possible to grow a plurality of single crystal rods from a crucible that can be used only once, and standards such as resistance are available. Two or more single crystal rods can be obtained in the same batch. Therefore, the production yield and cost of the carbon-doped silicon single crystal can be greatly improved as compared with the case where only one single crystal rod is grown per crucible.

  In the method for producing a carbon-doped silicon single crystal of the present invention, it is preferable to prepare a fiber-like and / or cloth-like carbon fiber and / or silicon carbide fiber as the dopant (claim 4).

Thus, if the carbon fiber and / or silicon carbide fiber used in the present invention is in the form of yarn and / or cloth, the effect of preventing scattering of the carbon dopant is high, and carbon is more accurately contained in the raw material melt. Can be doped.
Here, the filamentous carbon fiber and / or silicon carbide fiber refers to a bundle of several to several thousand carbon fibers and / or silicon carbide fibers in addition to the carbon fibers or silicon carbide fibers. Point to. The cloth-like carbon fiber and / or silicon carbide fiber refers to a cloth-like or sheet-like one produced by weaving yarn-like carbon fiber and / or silicon carbide fiber.

  Further, in the method for producing a carbon-doped silicon single crystal of the present invention, the crucible is filled with the carbon fiber and / or silicon carbide fiber, which is the dopant, around the silicon polycrystal prepared as a raw material. Preferred (claim 5).

  In this way, by winding the carbon fiber and / or silicon carbide fiber around the silicon polycrystal and filling the crucible into the crucible, the effect of preventing the scattering of the carbon dopant is further enhanced, and the melting of the fiber is also promoted. The Therefore, it becomes possible to dope carbon into the silicon single crystal with extremely high accuracy.

  Further, in the method for producing a carbon-doped silicon single crystal of the present invention, a filamentous carbon fiber and / or silicon carbide fiber is prepared as the dopant, and the filamentous carbon fiber and / or silicon carbide fiber as the dopant is prepared. The wound seed crystal is immersed in the raw material melt after crystal growth to melt the carbon fiber and / or silicon carbide fiber, and then the silicon polycrystal prepared as the raw material can be filled in the crucible. 6).

  Thus, if the filamentous carbon fiber and / or silicon carbide fiber is wound around the seed crystal and immersed in the raw material melt after the growth of the silicon single crystal, the scattering of the carbon fiber and / or silicon carbide fiber is surely prevented. In addition, a desired amount of carbon fiber and / or silicon carbide fiber can be dissolved in the raw material melt with high accuracy. Furthermore, according to this method, it is also possible to dope carbon without using any recharge tube for introducing an additional raw material into the crucible. When the recharge tube is not filled with a carbon dopant, the recharge tube is not contaminated with carbon, and carbon can be doped into the silicon single crystal with higher accuracy.

  Furthermore, this invention provides the carbon dope silicon single crystal manufactured by the manufacturing method of the carbon dope silicon single crystal of this invention (Claim 7).

  Since the carbon-doped silicon single crystal produced by the production method of the present invention uses carbon fibers and / or silicon carbide fibers, it is inexpensive and is doped with carbon with high accuracy.

  As described above, in the present invention, carbon fibers and / or silicon carbide fibers are used as a dopant to produce a carbon-doped silicon single crystal. Therefore, carbon can be easily and accurately doped in a silicon single crystal, and a carbon-doped silicon single crystal can be manufactured at low cost.

Hereinafter, the best mode for carrying out the present invention will be described, but the present invention is not limited thereto.
FIG. 2 is an example of a single crystal pulling apparatus used when carrying out the method for producing a carbon-doped silicon single crystal of the present invention. In the main chamber 1 of the single crystal pulling apparatus 20, there are provided a quartz crucible 5 for containing the melted raw material melt 4 and a graphite crucible 6 for supporting the quartz crucible 5. And the heater 7 is arrange | positioned so that these crucibles 5 and 6 may be enclosed. In order to prevent heat from the heater 7 from being directly radiated to the main chamber 1, a heat insulating member 8 is provided outside the heater 7 so as to surround the periphery thereof.

  A gas rectifying cylinder 11 is provided in the main chamber 1. Further, a heat insulating material 12 is provided at the outer lower end of the gas flow straightening cylinder 11 so as to face the raw material melt 4 to cut radiation from the melt surface and to keep the melt surface warm.

  The quartz crucible 5 is filled with polycrystalline silicon, which is a raw material for the carbon-doped silicon single crystal, and a dopant for doping carbon. At this time, a resistivity controlling dopant such as phosphorus or boron which determines the substrate resistivity of the carbon-doped silicon single crystal may be added.

The carbon dopant used in the production method of the present invention is carbon fiber and / or silicon carbide fiber. Carbon fiber and silicon carbide fiber are inexpensive and easily available in high purity. The purity of the carbon fiber or silicon carbide fiber is not particularly limited, but it is preferable to use carbon fiber or silicon carbide fiber having a purity as high as possible. This is because the use of high-purity carbon fiber or high-purity silicon carbide fiber can more reliably prevent the occurrence of defects such as OSF in the carbon-doped silicon single crystal due to impurities derived from carbon fiber or silicon carbide fiber. Here, the high-purity carbon fiber or the high-purity silicon carbide fiber refers to, for example, a carbon fiber or silicon carbide fiber having a purity of 99.99% or more and an ash content of 0.01% or less. In addition, if carbon fiber or silicon carbide fiber is used as a dopant, remelting is possible when the crystal is disturbed unlike the case of gas doping. Moreover, unlike the case of using high-purity carbon powder, there is little risk that the high-purity carbon powder will be scattered by the introduced gas or the like when the raw material is melted. Moreover, unlike the case of using a carbon lump, it dissolves quickly in the raw material melt. Furthermore, in order to prepare the dopant, it is not necessary to process almost, no heat treatment or the like is required, and the preparation of the carbon dopant is easy.
Therefore, carbon can be easily doped into the silicon single crystal with high accuracy. In addition, the carbon-doped silicon single crystal can be manufactured at low cost.

  Moreover, as a carbon fiber and / or silicon carbide fiber which is a dopant, a thread-like and / or cloth-like thing is preferable. In this way, if it is in the form of yarn and / or cloth, there is little risk of scattering by an inert gas such as Ar gas when melting into the raw material melt, and carbon is more reliably doped into the raw material melt. be able to. That is, the carbon fiber and / or silicon carbide fiber is cut into a predetermined length or size as a thread or cloth. By putting this in the crucible, a desired amount of carbon can be doped into the raw material melt.

  In particular, when thread-like carbon fibers and / or silicon carbide fibers are used as a dopant, the carbon fibers and / or silicon carbide fibers 22 are wound around the bulk silicon polycrystal 21 as a raw material, as shown in FIG. Thus, scattering of the carbon dopant can be prevented more reliably.

  In this way, after filling the quartz crucible 5 with the raw material and the dopant, an Ar gas is supplied from the gas inlet 10 installed in the pulling chamber 2 while operating a vacuum pump (not shown) and exhausting from the gas outlet 9. And the inside is replaced with an Ar atmosphere. Next, it heats with the heater 7 arrange | positioned so that the graphite crucible 6 may be surrounded, a raw material is fuse | melted and the raw material melt 4 is obtained.

  At this time, unlike the powder, the carbon fiber and / or silicon carbide fiber is less likely to be scattered by Ar gas. Therefore, almost all of the added carbon fibers and / or silicon carbide fibers are melted and dissolved in the raw material melt 4. Thus, since there is little possibility that the dopant is scattered and lost during melting, the carbon concentration in the raw material melt 4 can be controlled to a desired concentration with high accuracy.

  After melting the raw material filled in this way, the seed crystal 13 is immersed in the raw material melt and pulled up while rotating the seed crystal. Thereby, a rod-like silicon single crystal (silicon single crystal rod) 3 is grown under the seed crystal. Thus, a silicon single crystal doped with a desired concentration of carbon is manufactured.

Next, with reference to FIG. 3, the case where the multi-pooling method which grows several silicon single crystal from one crucible is implemented is demonstrated. The single crystal pulling apparatus used at this time will be described with reference to the apparatus of FIG.
As described above, the first silicon single crystal rod 3 is pulled up from the initial raw material melt 4 (A0, A1 in FIG. 3). Then, the pulled silicon single crystal rod 3 is taken out from the single crystal pulling apparatus 20 (A2 in FIG. 3). Thereafter, the power of the heater 7 is controlled so that only the surface of the raw material melt 4 is solidified.

Then, a silicon polycrystal having the same weight as the pulled silicon single crystal is prepared as an additional raw material, and this is filled into the quartz tube 30 together with carbon fibers and / or silicon carbide fibers prepared as a dopant.
If the doping agent is carbon fiber and / or silicon carbide fiber, carbon can be easily doped into the silicon single crystal with high accuracy. Moreover, since carbon fibers and silicon carbide fibers can be obtained at low cost, a carbon-doped silicon single crystal can be produced at low cost. Moreover, as a carbon fiber and / or silicon carbide fiber which is a dopant, a thread-like and / or cloth-like thing is preferable. This is because the use of a thread-like and / or cloth-like shape can more reliably prevent the dopant from being scattered. In particular, as shown in FIG. 1, the thread-like carbon fiber and / or silicon carbide fiber 22 is preferably wound around a massive silicon polycrystal 21 as a raw material. What is necessary is just to put the silicon polycrystal which wound this fiber in the said quartz tube. Thereby, scattering of a carbon dopant can be prevented reliably and carbon can be doped.

  Next, the silicon polycrystal and the carbon dopant filled in the quartz tube 30 are put on the solidified surface of the raw material melt 4 (A3 in FIG. 3). Next, while a vacuum pump (not shown) is operated and exhausted from the gas outlet 9, Ar gas is introduced from the gas inlet 10 installed in the pulling chamber 2, and the inside is replaced with an Ar atmosphere. Next, by heating with the heater 7, the additional raw material is melted to obtain the raw material melt 4 for growing the next silicon single crystal (A4 in FIG. 3). At this time, the carbon fibers and / or silicon carbide fibers dissolve in the raw material melt 4 without being scattered by Ar gas. Therefore, carbon is not lost during melting, and the carbon concentration in the raw material melt 4 can be controlled to a desired concentration with high accuracy.

  After melting the additional raw material, the seed crystal 13 is immersed in the raw material melt, and the seed crystal is pulled up while rotating to grow the next rod-shaped silicon single crystal 3 (A1 in FIG. 3). Thus, a silicon single crystal doped with a desired concentration of carbon is manufactured.

  In this case, two or more are repeated by repeating the process from the step of taking out the single crystal to the step of growing the carbon-doped silicon single crystal rod (that is, from A2 in FIG. 3 to A1 through A3 and A4). The carbon-doped silicon single crystal rod can be grown. Thereby, a plurality of single crystal rods can be grown from a crucible that can be used only once. In addition, more single crystal rods with uniform standards such as resistance can be obtained from the same batch, and the ratio of crystals within the standard to the raw materials used is greatly increased. Therefore, compared with the case where only one single crystal rod is grown per crucible, the production yield and production cost of the carbon-doped silicon single crystal can be greatly improved.

  Further, before filling the crucible with silicon polycrystal prepared as an additional raw material (that is, between A2 and A3 in FIG. 3), the carbon fiber is wound around the seed crystal with thread-like carbon fibers and / or silicon carbide fibers. Alternatively, the seed crystal around which the silicon carbide fiber is wound may be immersed in the raw material melt after crystal growth, and the carbon fiber and / or the silicon carbide fiber may be melted together with a part of the seed crystal. In this case, when silicon carbide fibers are used, the specific gravity is heavier than that of the silicon melt, so that the silicon carbide fibers can sink and dissolve in the raw material melt after being immersed in the raw material melt. Can melt.

Thus, if the carbon fiber and / or silicon carbide fiber is wound around the seed crystal and immersed in the raw material melt after the growth of the silicon single crystal, the carbon fiber and / or silicon carbide fiber is surely prevented from scattering. The desired amount of carbon fiber and / or silicon carbide fiber can be dissolved in the raw material melt with high accuracy. Furthermore, according to this method, it is possible to dope carbon without using the recharge tube 30 at all. In this case, since the recharge tube 30 is not filled with a carbon dopant, the recharge tube is not contaminated with carbon, and carbon can be doped into the silicon single crystal with high accuracy even when the recharge tube is reused.
Of course, the carbon dopant may be added using both a recharge tube and a seed crystal.

  In the above description, the case where a bulk silicon polycrystal as a raw material is additionally charged in a crucible using a quartz tube has been described. However, granular silicon polycrystal can be additionally charged into the crucible with a feeder as a raw material. In this case, the carbon fiber dopant can be fed together with the granular polycrystal by a feeder.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.
Example 1
In order to set the carbon concentration at the shoulder to 5 × 10 ¹⁶ atoms / cm ³ (Old ASTM), a carbon-doped silicon single crystal rod was grown by the following method.
First, a thread-like carbon fiber having a diameter of 0.3 mm was cut at 1.6 g. The cut filamentary carbon fiber was used as a dopant. Next, as shown in FIG. 1, the cut filamentary carbon fiber (dope) 22 was wound around the massive silicon polycrystal 21. Then, 160 kg of silicon polycrystal prepared as a raw material and 1.6 g of carbon fiber wound around the silicon polycrystal were filled into a quartz crucible having a diameter of 24 inches (600 mm). Next, the heater was heated to melt the silicon polycrystalline material in the crucible. As a precaution, the heater power during melting for 1 hour was maintained even after the silicon polycrystalline raw material was melted, and the carbon fibers were melted securely. Thereafter, a carbon-doped silicon single crystal having a diameter of 200 mm and a straight body length of 100 cm was grown from this raw material melt.

And about this grown carbon dope silicon single crystal, carbon concentration of a shoulder part and lifetime of a tail part were measured. This was carried out for 5 batches.
As a result, the carbon concentration was an average value = 4.97 × 10 ¹⁶ atoms / cm ³ (Old ASTM), and σ = 0.1. This is a concentration very close to the target carbon concentration (5 × 10 ¹⁶ atoms / cm ³ (Old ASTM)). Also, the variation in density is very small.
Further, the lifetime was an average value of 581 μsec and σ = 17.

(Example 2)
Next, a single crystal rod was grown by the following method in order to set the carbon concentration at the shoulder to 5 × 10 ¹⁶ atoms / cm ³ (Old ASTM).
A thread-like carbon fiber having a diameter of 0.3 mm was cut at 1.0 g. The cut filamentary carbon fiber was used as a dopant. Next, as shown in FIG. 1, the cut filamentary carbon fiber (dope) 22 was wound around the massive silicon polycrystal 21. Then, 90 kg of silicon polycrystal prepared as an additional raw material and 1.0 g of thread-like carbon fiber wound around the silicon polycrystal were put into quartz in a crucible after silicon single crystal growth by the same method as in Example 1. Filled with a tube. Next, the heater was heated to melt the additional raw material in the crucible. As a precaution, the heater power at the time of melting for 1 hour was maintained even after the added silicon polycrystalline raw material was melted, and the carbon fiber was melted securely. Thereafter, a silicon single crystal having a diameter of 200 mm and a straight body length of 100 cm was grown from the added raw material melt.

The carbon concentration of the shoulder and the lifetime of the tail of the grown carbon-doped silicon single crystal were measured. This was carried out for 5 batches.
As a result, the carbon concentration was an average value = 4.94 × 10 ¹⁶ atoms / cm ³ (Old ASTM), and σ = 0.15. This is a concentration very close to the target carbon concentration (5 × 10 ¹⁶ atoms / cm ³ (Old ASTM)). Also, the variation in density is very small.
The lifetime was 605 μsec on average and σ = 26.

(Example 3)
Next, a single crystal rod was grown by the following method in order to set the carbon concentration at the shoulder to 5 × 10 ¹⁶ atoms / cm ³ (Old ASTM).
First, a thread-like silicon carbide fiber having a diameter of 0.3 mm was cut at 2.2 g. The cut thread-like silicon carbide fiber was used as a dopant. Next, the cut thread-like silicon carbide fiber (dope agent) was wound around the seed crystal. And the seed crystal around which the thread-like silicon carbide fiber was wound was set in the seed holder. And this was immersed in the raw material melt after the silicon single crystal growth by the method similar to Example 1, and the silicon carbide fiber was melted together with a part of the seed crystal. Thereafter, 90 kg of silicon polycrystal prepared as an additional raw material was filled into the crucible using a quartz tube. Next, the heater was heated to melt the additional raw material in the crucible. Thereafter, a silicon single crystal having a diameter of 200 mm and a straight body length of 100 cm was grown from the added raw material melt.

The carbon concentration of the shoulder and the lifetime of the tail of the grown carbon-doped silicon single crystal were measured. This was carried out for 5 batches.
As a result, the carbon concentration was an average value = 5.04 × 10 ¹⁶ atoms / cm ³ (Old ASTM), and σ = 0.05. This is a concentration very close to the target carbon concentration (5 × 10 ¹⁶ atoms / cm ³ (Old ASTM)). Also, the variation in density is very small.
The lifetime was 590 μsec on average and σ = 34.

(Comparative Example 1)
In order to set the carbon concentration at the shoulder to 5 × 10 ¹⁶ atoms / cm ³ (Old ASTM), a carbon-doped silicon single crystal rod was grown by the following method.
First, 1.6 g of carbon powder was prepared as a dopant. Next, 1.6 g of carbon powder together with 160 kg of polycrystalline silicon raw material prepared as a raw material was filled in a quartz crucible having a diameter of 24 inches (600 mm). Next, the heater was heated to melt the silicon polycrystalline material. As a precaution, even after the silicon polycrystalline raw material was melted, the heater power during melting for 1 hour was maintained, and the carbon powder was reliably melted. Thereafter, a silicon single crystal having a diameter of 200 mm and a straight body length of 100 cm was grown from this raw material melt.

And about this grown carbon dope silicon single crystal, carbon concentration of a shoulder part and lifetime of a tail part were measured. This was carried out for 5 batches.
As a result, the carbon concentration was an average value = 3.0 × 10 ¹⁶ atoms / cm ³ (Old ASTM), and σ = 0.89. This is 40% lower than the target carbon concentration (5 × 10 ¹⁶ atoms / cm ³ (Old ASTM)). Moreover, there is a large variation in concentration between batches.
The lifetime was 603 μsec on average and σ = 32.

(Comparative Example 2)
Next, in order to set the carbon concentration at the shoulder to 5 × 10 ¹⁶ atoms / cm ³ (Old ASTM), a carbon-doped silicon single crystal rod was grown by the following method.
First, 1.0 g of carbon powder was prepared as a dopant. Then, 90 kg of silicon polycrystalline raw material prepared as an additional raw material and 1.0 g of carbon powder were filled into a crucible after silicon single crystal growth by the same method as in Example 1 using a quartz tube. Next, the heater was heated to melt the silicon polycrystalline material. As a precaution, the heater power during melting for 1 hour was maintained and the carbon powder was reliably melted. Thereafter, a silicon single crystal having a diameter of 200 mm and a straight body length of 100 cm was grown.

With respect to the grown carbon-doped silicon single crystal, the lifetime of the shoulder portion and the tail portion was measured. This was carried out for 5 batches.
As a result, the carbon concentration was an average value = 3.7 × 10 ¹⁶ atoms / cm ³ (Old ASTM), and σ = 0.76. This is a concentration 24% lower than the target carbon concentration (5 × 10 ¹⁶ atoms / cm ³ (Old ASTM)). Moreover, as in Comparative Example 1, there is a large variation in concentration between batches.
The lifetime was 605 μsec on average and σ = 36.

  Table 1 below summarizes the results of Examples 1 to 3 and Comparative Examples 1 and 2.

As can be seen from Table 1, if the methods of Examples 1 to 3 are used, the carbon concentration in the silicon single crystal can be controlled to a target concentration (5 × 10 ¹⁶ atoms / cm ³ (Old ASTM)) with high accuracy. Is possible. On the other hand, in the methods of Comparative Examples 1 and 2, the target carbon concentration is far from the target, and the variation of the carbon concentration between batches is large, and the carbon concentration in the silicon single crystal is controlled only with low accuracy. I can't understand.

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

It is the schematic which shows the silicon polycrystal which wound carbon fiber or silicon carbide fiber. It is the schematic which shows a single crystal pulling apparatus. It is explanatory drawing which shows the multi pooling method.

Explanation of symbols

1 ... main chamber, 2 ... pulling chamber, 3 ... silicon single crystal rod,
4 ... Raw material melt, 5 ... Quartz crucible, 6 ... Graphite crucible, 7 ... Heater,
8 ... heat insulating member, 9 ... gas outlet, 10 ... gas inlet,
DESCRIPTION OF SYMBOLS 11 ... Gas rectifier cylinder, 12 ... Thermal insulation, 13 ... Seed crystal, 20 ... Single crystal pulling apparatus,
21 ... polycrystalline silicon, 22 ... carbon fiber or silicon carbide fiber,
30: Quartz tube.

Claims (7)

  In the method for producing a silicon single crystal by doping carbon by the Czochralski method, at least the step of preparing carbon fiber and / or silicon carbide fiber as a dopant, the carbon fiber together with the silicon polycrystal prepared as a raw material and / Or filling the crucible with a dopant comprising silicon carbide fibers; melting the filled raw material into a raw material melt; and growing a carbon-doped silicon single crystal rod from the raw material melt; A method for producing a carbon-doped silicon single crystal comprising:   In the method for producing a silicon single crystal by doping carbon by the Czochralski method, at least a step of growing a silicon single crystal rod from an initial raw material melt contained in a crucible, and taking out the grown silicon single crystal rod A step, a step of preparing carbon fibers and / or silicon carbide fibers as a dopant, and a step of filling a crucible with a silicon polycrystal prepared as an additional raw material and the carbon fiber and / or silicon carbide fibers. A method for producing a carbon-doped silicon single crystal, comprising: melting the additional raw material; and growing a carbon-doped silicon single crystal rod from the added raw material melt.   Further, two or more carbon-doped silicon single crystal rods are grown by repeating from the step of taking out the single crystal to the step of growing the carbon-doped silicon single crystal rod. A method for producing a carbon-doped silicon single crystal.   The carbon-doped silicon unit according to any one of claims 1 to 3, wherein the carbon fiber and / or silicon carbide fiber as the dopant is prepared in a thread form and / or a cloth form. Crystal production method.   5. The carbon-doped silicon single crystal according to claim 4, wherein the carbon fiber and / or silicon carbide fiber as the dopant is wound around a silicon polycrystal prepared as a raw material and filled in a crucible. Production method.   As the dopant, a filamentous carbon fiber and / or silicon carbide fiber is prepared, and a seed crystal around which the filamentous carbon fiber and / or silicon carbide fiber as the dopant is wound is immersed in the raw material melt after crystal growth. The carbon according to any one of claims 2 to 5, wherein the carbon fiber and / or the silicon carbide fiber is melted, and then the silicon polycrystal prepared as a raw material is filled in the crucible. A method for producing a doped silicon single crystal.   The carbon dope silicon single crystal manufactured by the manufacturing method of the carbon dope silicon single crystal of any one of Claim 1 thru | or 6.

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