JP5070737B2 - Method for producing FZ single crystal silicon using silicon crystal rod produced by CZ method as raw material - Google Patents

Description

  The present invention relates to a method for producing a silicon single crystal by FZ method (floating zone method or floating zone melting method), and more specifically, high-quality P-type or N-type silicon having a predetermined resistivity by FZ method. The present invention relates to a method for producing a single crystal.

  Conventionally, silicon wafers manufactured by the FZ method have been used for manufacturing power devices such as high voltage power devices and thyristors. In recent years, in order to improve the performance of semiconductor devices and reduce costs, a large-diameter silicon wafer has been demanded, and accordingly, growth of a large-diameter silicon single crystal has been demanded.

  When producing a silicon single crystal by the FZ method, the tip of a silicon polycrystalline material rod is melted by high-frequency induction heating using a heater coil or the like in an inert gas atmosphere such as argon, and brought into contact with a seed crystal. Thereafter, the partial melting zone is usually moved from the lower part to the upper part of the raw material rod, thereby performing single crystallization having the same crystal axis as that of the seed crystal.

Further, as a method of controlling the resistivity of a silicon single crystal (FZ single crystal silicon) manufactured by the FZ method to a predetermined resistivity, an N-type single crystal is formed when single crystallization is performed by the FZ method. In the case of phosphine (PH ₃ ) in the case of P-type single crystal, argon gas containing diborane (B ₂ H ₆ ) in the case of P-type single crystal is sprayed on the melted part using a nozzle according to a predetermined resistivity (for example, Non-Patent Document 1), and after growing a silicon single crystal by the FZ method without doping a dopant (non-doped), the single crystal rod is inserted into a nuclear reactor and irradiated with neutrons. method for doping with a dopant that changes the ³⁰ Si to ³¹ P nuclear reaction (Neutron Transmutation doping, NTD) (non-Patent Document 2, Patent Document 1) That.

  Usually, rod-shaped polycrystalline silicon is used as a raw material for FZ single crystal silicon. However, the polycrystalline silicon (polycrystalline silicon rod for FZ) required as a raw material in the FZ method has high purity, hardly generates cracks and cracks, has a uniform grain boundary structure, and is suitable for FZ single crystal silicon to be manufactured. It is necessary to have a cylindrical shape with a good surface condition with a flat diameter and a small number of diameters. The manufacture of such a polycrystalline silicon rod for FZ is very low in yield and productivity as compared with the manufacture of nugget-like polycrystalline silicon used in the CZ method.

  In addition, in recent years, the demand for polycrystalline silicon (polycrystalline silicon for CZ) used in the CZ method centering on 300 mm diameter has increased significantly, and there has also been a demand for polycrystalline silicon for solar cells. It is increasing rapidly. Because of this, quality standards such as shape and purity are strict, the productivity is low, and the supply of high-cost polycrystalline silicon rods for FZ is tight against the demand, and the price is also very high. Yes. As a result, it becomes difficult to secure high-quality polycrystalline silicon for FZ, and it has become difficult to stably manufacture FZ single-crystal silicon.

WOLFGANG KELLER, ALFRED MUHLBAUER, “Floating-zone silicon”, MARCEL DEKER INC. Issue, pp. 82-92 WOLFGANG KELLER, ALFRED MUHLBAUER, “Floating-zone silicon”, MARCEL DEKER INC. Issue, pp. 93-95 Japanese Patent Laid-Open No. 50-94880

  The present invention has been made in view of the above problems, and an object of the present invention is to use a raw material that can provide a high-quality and stable supply instead of an expensive polycrystalline silicon raw material rod used in the FZ method. Accordingly, an object of the present invention is to provide a method for stably producing a silicon single crystal produced by the FZ method with a predetermined resistivity.

In order to achieve the above object, a silicon single crystal manufacturing method by the FZ method, wherein a P-type or N-type silicon crystal rod having a resistivity of 50 Ω · cm or more manufactured by the CZ method is used as a silicon raw material rod, the silicon A silicon single crystal characterized by recrystallizing the silicon raw material rod into a P-type or N-type silicon single crystal having a desired resistivity by gas doping the raw material rod with an impurity having the same conductivity type as the silicon raw material rod that provides a method of manufacturing.

Thus, by producing a silicon raw material rod of the FZ method by the CZ method, it is possible to stably produce a uniform silicon crystal rod having high purity and being less prone to cracks and cracks. Furthermore, a silicon raw material rod suitable for the diameter of the silicon single crystal to be produced by the FZ method can be produced, and a silicon raw material rod having a flat surface, a small crank, a good surface state, and the like can be stably supplied.
And since the silicon raw material rod manufactured by the CZ method inevitably contains oxygen, the oxygen concentration tends to be high, but when performing zoning by the FZ method, oxygen contained in the raw material rod can be scattered, It is possible to obtain a silicon single crystal having a low oxygen concentration that is equivalent to that obtained when polycrystalline silicon often used in the FZ method of 0.5 ppma or less is used as a raw material.
Further, by gas doping impurities having the same conductivity type as that of the silicon raw material rod, it is not necessary to gas dope impurities having the same conductivity type as that of the silicon raw material rod, so that it is easy to control the desired resistivity and FZ has good electrical characteristics. It becomes a silicon single crystal.

In addition, the gas dope recrystallizes the silicon raw material rod into a silicon single crystal by changing the flow rate of the doping gas in the axial direction according to the axial distribution of resistivity of the silicon raw material rod. that provides a method of manufacturing a crystal.
As described above, in the FZ method, by changing the doping gas flow rate in the axial direction according to the axial distribution of the resistivity of the silicon raw material rod, there is a difference in the axial resistivity of the silicon raw material rod produced by the CZ method. Even in some cases, an FZ silicon single crystal having a uniform distribution in the axial direction can be manufactured.

In this case, the resistivity of the silicon feed rod manufactured by the CZ method Ru can be 500 [Omega · cm or more.
When the resistivity of the silicon raw material rod produced by the CZ method is low, the concentration of the segregated dopant in the crystal in the axial direction increases due to the effect of segregation by the CZ method. There is a possibility that the dopant concentration to be added increases, and even if the doping gas flow rate is changed, it is impossible to follow the axial resistivity change. Therefore, in the present invention, the resistance of the CZ crystal rod needs to be 50 Ω · cm or more, but further, by making the resistivity of the silicon raw material rod 500 Ω · cm or more, the single crystal by FZ method made by gas doping The change in resistivity in the axial direction can be reduced.

Further, the present invention is a method for producing a silicon single crystal by the FZ method, wherein a non-doped silicon crystal rod produced by the CZ method is used as a silicon raw material rod, and the silicon raw material rod is recrystallized non-doped by the FZ method. performing a neutron irradiation that provides a method for manufacturing a silicon single crystal, wherein the after.
As described above, the non-doped silicon raw material rod produced by the CZ method is recrystallized non-doped by the FZ method and then neutron irradiation is performed, thereby stably stabilizing the silicon single crystal produced by the FZ method without doping. The resistivity can be controlled to a predetermined resistivity.

  In the method for producing a silicon single crystal according to the present invention, a polycrystalline silicon raw material rod that has been conventionally used in the FZ method is in short supply and the price is rising. By using it as a rod, a high-quality silicon single crystal can be produced stably.

Hereinafter, the present invention will be described in detail.
With the recent increase in diameter of silicon wafers, the demand for polycrystalline silicon for CZ is increasing, and the demand for polycrystalline silicon for solar cells is also increasing rapidly. The quality standards such as shape and purity are strict, the productivity is low, and the cost is high, and the FZ polycrystalline silicon rod is tightly supplied with the demand, and the price is very high. Therefore, since it is difficult to secure a high-quality FZ polycrystalline silicon rod, it is difficult to produce stable FZ single crystal silicon.

  On the other hand, when CZ single crystal silicon is used as it is as a raw material silicon rod for FZ, there are two major problems. First, in the CZ method, nugget-like polycrystalline silicon is placed in a quartz crucible, melted, seed crystals are attached to the surface of the melt, and pulled up to grow CZ single crystal silicon. Since the melt is in contact with the quartz crucible, 10 to 20 ppma of oxygen is mixed into the produced silicon single crystal from the quartz crucible. The resistivity of oxygen in the crystal changes due to the influence of an oxygen donor generated by heat treatment during crystal growth or device manufacturing, which adversely affects device characteristics. Secondly, in the CZ method, the resistivity decreases as it goes from the cone side to the tail side due to the effect of segregation, and thus crystals having a predetermined narrow resistivity tolerance cannot be manufactured with a high yield.

  In contrast to this reality, the inventor of the present invention makes the polycrystalline silicon for CZ nugget-like, so it is cheaper and more stable and easier to obtain than the polycrystalline silicon raw material rod for FZ. It was considered that a silicon raw material rod for FZ could be stably produced by using easy CZ single crystal silicon as a silicon raw material rod for the FZ method.

  Further, the present inventor uses a high-resistivity CZ single crystal silicon rod of 50 Ω · cm or more as a raw material, performs zoning by the FZ method while doping a dopant having the same conductivity type as the raw material rod, and recrystallizes it. The oxygen in the silicon single crystal is scattered from the surface of the melt, and as a result, the oxygen concentration in the FZ silicon single crystal is extremely low, and the production of the silicon single crystal having a desired resistivity, for example, 1000Ω · cm or less is stabilized The present invention has been completed.

  In order to obtain a silicon wafer having a large diameter and a high resistivity, a silicon raw material rod having a resistivity of 1000 Ω · cm or more manufactured by the CZ method is re-converted into a silicon single crystal having a resistivity of 1000 Ω · cm or more by the FZ method. There is a method of crystallizing and gas-doping an impurity having a conductivity type opposite to the conductivity type of the silicon raw material rod during the recrystallization to produce a silicon single crystal having a high resistivity of 3000 Ω · cm or more. It is disclosed in JP-A-2005-306653.

  However, in this manufacturing method, when the gas doping is performed in the FZ method, an impurity having a conductivity type opposite to the impurity doped by the CZ method is gas-doped. The amount is very small. Therefore, even if it is difficult to control the resistivity and a desired resistivity cannot be obtained or a silicon single crystal having a high resistivity of 1000 Ω · cm or more can be manufactured, the P type and the N type are practically used. Since both of these impurities are mixed, problems in electrical characteristics may occur.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

  FIG. 2 is a manufacturing flow of conventional FZ single crystal silicon, and FIG. 3 is a manufacturing flow of FZ single crystal silicon using CZ single crystal silicon as a raw material in the present invention.

  First, a silicon raw material rod used for a silicon single crystal manufactured by the FZ method, for example, a silicon crystal rod having a diameter of 100 to 150 mm is grown by the CZ method. For example, when growing a silicon crystal rod having a diameter of 130 mm, for example, a quartz crucible having a diameter of 450 mm is filled with 60 kg of nugget-like silicon polycrystal, and then the seed crystal is immersed in a raw material melt obtained by heating and melting the silicon polycrystal with a heater. For example, a silicon crystal having a diameter of 130 mm and a straight body length of 100 cm is grown at a predetermined growth rate while rotating the seed crystal. At this time, for example, the oxygen concentration and the carbon concentration are not particularly limited. The crystal orientation is preferably the same as that of the silicon single crystal finally produced by the FZ method, but it is not necessarily required to be a complete single crystal. This is because complete single crystallization can be achieved in the FZ method.

  Note that when a silicon crystal rod is grown by the CZ method, a predetermined amount of dopant may be introduced into the quartz crucible so as to obtain a desired resistivity. As the dopant, for example, when the conductivity type is P-type, boron or gallium is used, and when the conductivity type is N-type, a silicon piece doped with phosphorus, arsenic, antimony, or the like at a high concentration is used. It can dope by putting in a quartz crucible. At this time, in the present invention, the resistivity of the crystal manufactured by the CZ method is 50 Ω · cm or more, more preferably 500 Ω · cm or more (FIG. 3A) or non-doping (FIG. 3B). This is because the concentration of the dopant segregated in the CZ method can be lowered by setting the resistivity of the crystal manufactured by the CZ method to 50 Ω · cm or more, and this is corrected by gas doping during zoning in the FZ method. The resistivity can be controlled during crystal growth. Moreover, since the dopant concentration segregated by the CZ method can be further reduced by setting the resistivity of the crystal manufactured by the CZ method to 500 Ω · cm or more, the axial direction of the FZ method silicon single crystal formed by gas doping can be reduced. Resistivity change can be reduced.

  Next, after cylindrical grinding of the silicon crystal rod thus obtained by the CZ method, the portion where melting is started by the FZ method is processed into a cone shape, and then the surface is etched to remove the processing strain. Comparing the diameter variation of CZ single crystal silicon immediately after growth (FIG. 4B) and the diameter variation of conventional FZ polycrystalline silicon (FIG. 4A), the diameter variation of CZ single crystal silicon is It can be seen that it is less than half of the diameter variation of polycrystalline silicon. As a result, CZ single crystal silicon can reduce the amount of machining allowance in the circular grinding process performed to make the raw material rod have an appropriate diameter, as compared with polycrystalline silicon for FZ. Furthermore, the polycrystalline silicon raw material for CZ is 1/2 to 1/3 cheaper than the polycrystalline silicon rod for FZ, has many manufacturing companies, and has a large production volume. By using the raw material rod, it becomes possible to produce stable and high-quality FZ single crystal silicon.

  Then, as shown in FIG. 1, an upper holding jig 4 of an upper shaft 3 installed in a chamber 20 of an FZ single crystal manufacturing apparatus 30 is used for a P-type or N-type silicon crystal rod 1 manufactured by the CZ method. A silicon raw material rod 1 is fixed to the lower holding jig 6 of the lower shaft 5 with a silicon single crystal seed (seed crystal) 8 having a small diameter.

  Next, the lower end of the cone portion of the silicon raw material rod 1 is preheated with a carbon ring (not shown). Thereafter, Ar gas containing nitrogen gas is supplied from the lower part of the chamber 20 and exhausted from the upper part of the chamber 20. For example, the flow rate of Ar gas is 20 l / min, and the nitrogen concentration in the chamber is 0.5%. After the silicon raw material rod 1 is heated and melted by the induction heating coil (high frequency coil) 7, the tip of the cone portion is fused to the seed crystal 8, the dislocation is made free by the narrowed portion 9, and the upper shaft 3 and the lower shaft 5 are rotated. The silicon raw material rod 1 is lowered at a growth rate of, for example, 2.0 mm / min while moving the floating zone 10 to the upper end of the silicon raw material rod to perform zoning, and the silicon raw material rod 1 is recrystallized to form the silicon single crystal 2. Grow. At this time, the upper shaft 3 serving as the center of rotation when growing the silicon raw material rod 1 and the lower shaft 5 serving as the center of rotation of the single crystal during recrystallization are shifted (eccentric) to form a single crystal. It is preferable to train. By shifting both centers in this way, the molten state can be stirred during recrystallization, and the quality of the in-plane resistivity distribution and the like of the silicon single crystal to be manufactured can be made uniform. The amount of eccentricity may be set according to the diameter of the silicon single crystal, for example, about 10 mm.

  In this way, oxygen inevitably contained in the silicon raw material rod produced by the CZ method can be scattered out of the molten zone, so that the oxygen concentration in the FZ single crystal can be made extremely low. As a result, 350 Even if heat treatment at ˜500 ° C. is performed, an FZ silicon single crystal in which no oxygen donor is generated can be obtained.

  If the atmosphere in the chamber contains nitrogen as described above, the silicon single crystal is doped with nitrogen, and FPD (Flow Pattern Defect) and swirl defects existing inside the silicon raw material rod 1 disappear. A high quality silicon single crystal can be grown, which is preferable. In this case, the nitrogen concentration in the atmosphere is not limited to the above 0.5%, and if it is 0.2 to 0.5%, it is preferable because nitrogen is doped at an appropriate concentration to eliminate the above defects. . Further, instead of nitrogen gas, a compound gas containing nitrogen such as ammonia, hydrazine, or nitrogen trifluoride may be used.

Doping the dopant for controlling the resistivity is performed by blowing a doping gas containing a very small amount of dopant gas of the same conductivity type as the silicon raw material rod from the doping gas nozzle 11 to the floating zone 10 at a predetermined flow rate according to a known method. Can do. For example, if the silicon raw material rod is N-type, a doping gas in which phosphine (PH ₃ ) is contained in Ar gas or the like in a trace amount can be used as the dopant gas. If it is P-type, diborane (B ₂ H ₆ ) Can be used.

  In this gas doping, a CZ single crystal silicon manufactured by adding a small amount of dopant, for example, a silicon raw material rod having a resistivity of about 50 Ω · cm, and when the difference in dopant concentration in the crystals of the cone and tail is large, The predetermined resistivity can be controlled to be substantially constant in the axial direction by changing the flow rate of the doping gas in accordance with the change in the dopant concentration in the direction. That is, when the tail side (that is, the low resistance side) of the CZ crystal, which is the raw material rod, is set downward, the dopant gas gradually increases the flow rate during the growth of FZ single crystal silicon, thereby increasing the axial resistivity. Can be constant. Conversely, when the cone side (that is, the high resistance side) of the CZ crystal is set downward, the dope gas flow rate may be gradually decreased. Furthermore, the amount of gas doping can be reduced by making the difference in dopant concentration in the cone and tail crystals of CZ single crystal silicon extremely small, and the axial resistivity can be made almost constant. Therefore, it is preferable that CZ single crystal silicon has a high resistivity of 500 Ω · cm or more by making the doping amount extremely small.

  Further, if an impurity (dopant) having the same conductivity type as that of the silicon raw material rod is gas-doped, the same conductivity type as that of the silicon raw material rod is obtained without mixing the P-type dopant and the N-type dopant, and the electrical characteristics. It is possible to obtain a silicon single crystal having a good predetermined resistivity.

In addition, when recrystallizing a silicon crystal rod manufactured by the CZ method by the FZ method, if the CZ method, the FZ method, or the non-doping method is used, in order to control the resistivity, neutron irradiation is performed in a nuclear reactor by a known method. By performing the above, it is possible to manufacture an N-type silicon single crystal with a predetermined resistivity. In this case, the gas dope is advantageous in that it is low-cost and can be manufactured in both N-type and P-type, and non-doped CZ single crystal silicon is zoned non-doped by the FZ method and irradiated with neutrons. Si ³⁰ contained in an amount of about% becomes Si ³¹ , which β decays and changes to P. Since Si ³⁰ is uniformly contained in the crystal, there is an advantage that P is made uniform by neutron irradiation, and a material having a more uniform resistivity than gas dope can be obtained.

  Then, by performing recrystallization by the FZ method as described above, the oxygen concentration contained in the silicon single crystal can be easily reduced to 0.5 ppma or less. With such an extremely low oxygen concentration, the formation of oxygen donors can be reliably prevented even when the silicon single crystal produced in the present invention is subjected to a heat treatment at about 350 to 500 ° C. Therefore, the silicon single crystal manufactured in this way becomes an FZ wafer having a predetermined resistivity in which the resistivity does not change reliably in the device manufacturing process.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.
Example 1
Using the FZ single crystal manufacturing apparatus shown in FIG. 1 as a raw material rod, CZ single crystal silicon having a diameter of 130 mm and N-type resistivity of 500 Ω · cm to 12,000 Ω · cm is used as a raw material rod, and the diameter is 128 mm. A silicon single crystal having a straight body length of about 80 cm was manufactured non-doped.
At this time, the Ar gas flow rate was 20 l / min, the nitrogen gas concentration in the chamber was 0.5%, the growth rate of the silicon single crystal was 2.0 mm / min, and the eccentricity was 10 mm.
And the silicon single crystal was grown 34 times by FZ method.

As a result, the resistivity of the manufactured FZ single crystal silicon was 495 Ω · cm to 12,100 Ω · cm in the N type as shown in FIG. As shown in FIG. 6, the oxygen concentration in the CZ crystal before FZ is about 14 to 20 ppma, but is 0.15 ppma to 0.46 ppma after FZ, and is usually mixed from the quartz crucible by the CZ method. From 10 to 20 ppma, the value was extremely low. Also, the carbon concentration was 0.06 ppma or less after FZ as shown in FIG.
The resistivity of CZ single crystal silicon used as a raw material rod was measured with a four-probe after sample wafers were taken from the cone side and the tail side and subjected to heat treatment at 650 ° C. for 20 minutes to eliminate oxygen donors. .

(Example 2)
Using a CZ single crystal silicon having a diameter of 130 mm as a raw material rod, zoning was performed by the FZ method using the FZ single crystal manufacturing apparatus shown in FIG. 1, and a silicon single crystal having a diameter of 128 mm and a straight body length of about 80 cm was manufactured. At that time, a dopant gas in which phosphine (PH ₃ ) was diluted to 2.5 ppm with argon was sprayed into the floating zone at a constant rate of 100 cc / min, and gas doping was performed.
At this time, the Ar gas flow rate was 20 l / min, the nitrogen gas concentration in the chamber was 0.5%, the growth rate of the silicon single crystal was 2.0 mm / min, and the eccentricity was 10 mm.

As a result, as shown in FIG. 8A, CZ single crystal silicon having a N-type resistivity of 15,600 Ω · cm and a N-type resistivity of 92,300 Ω · cm was used as a raw material rod. In this case, the resistivity of the manufactured FZ single crystal silicon was N-type 50.8 Ω · cm and substantially uniform in the axial direction as shown in FIG. 8B. The manufactured FZ single crystal silicon had an oxygen concentration of 0.20 ppma and a carbon concentration of less than 0.05 ppma.
In addition, although the resistivity of the raw material silicon rod produced by the CZ method is reversed between the cone side and the tail side, when the CZ method is performed without doping, since the amount of impurities is very small, the resistance becomes extremely high, A phenomenon in which the resistance becomes higher on the tail side due to the compensation of impurities inevitably mixed on the tail side is often seen.

(Example 3)
Using a non-doped CZ single crystal silicon having a diameter of 130 mm as a raw material rod, zoning is performed by the FZ method using the FZ single crystal manufacturing apparatus shown in FIG. 1, and a silicon single crystal having a diameter of 153 mm and a straight body length of about 40 cm is non-doped. Manufactured.
At this time, the Ar gas flow rate was 20 l / min, the nitrogen gas concentration in the chamber was 0.5%, the growth rate of the silicon single crystal was 2.0 mm / min, and the eccentricity was 10 mm.
The manufactured FZ single crystal was divided into three, and one block was irradiated with neutrons in a nuclear reactor.

  As a result, as shown in FIG. 9A, when CZ single crystal silicon having a cone-side resistivity of N-type 7,510 Ω · cm and a tail-side resistivity of N-type 2,500 Ω · cm is used as a raw material. Further, the resistivity of the manufactured FZ single crystal silicon is 7,830 Ω · cm to 12,840 Ω · cm as shown in FIG. 9B, and the resistivity of the manufactured neutron irradiated crystal is As shown in FIG. 9 (C), the N-type was 64.5 Ω · cm and was substantially uniform in the axial direction. The produced silicon single crystal had an oxygen concentration of 0.15 ppma and a carbon concentration of less than 0.05 ppma.

Example 4
Using a CZ single crystal silicon having a diameter of 130 mm as a raw material rod, zoning was performed by the FZ method using the FZ single crystal manufacturing apparatus shown in FIG. 1, and a silicon single crystal having a diameter of 128 mm and a straight body length of about 80 cm was manufactured. At that time, a dopant gas obtained by diluting phosphine (PH ₃ ) with argon to 0.15 ppm is changed from 1,000 cc / min depending on the length of the straight body of the single crystal to be grown as shown in FIG. , 700 cc / min, and sprayed to the floating zone to perform gas doping.
At this time, the Ar gas flow rate was 20 l / min, the nitrogen gas concentration in the chamber was 0.5%, the growth rate of the silicon single crystal was 2.0 mm / min, and the eccentricity was 10 mm.

  As a result, as shown in FIG. 10 (A), CZ single crystal silicon having a cone-side resistivity of N-type 100 Ω · cm and a tail-side resistivity of N-type 57.5 Ω · cm is used as a raw material rod. The resistivity of the manufactured FZ single crystal silicon was N-type 30.4 Ω · cm and substantially uniform in the axial direction as shown in FIG. The produced silicon single crystal had an oxygen concentration of 0.30 ppma and a carbon concentration of less than 0.05 ppma.

(Comparative Example 1)
Using the FZ single crystal manufacturing equipment shown in Fig. 1 as a raw material rod, N-type polycrystalline silicon for FZ having a diameter of 130 mm and N-type resistivity of 3,000 Ω · cm, zoning is performed by the FZ method, and the diameter is 128 mm. A silicon single crystal having a thickness of about 80 cm was produced without doping.
At this time, the Ar gas flow rate was 20 l / min, the nitrogen gas concentration in the chamber was 0.5%, the growth rate of the silicon single crystal was 2.0 mm / min, and the eccentricity was 10 mm.

As a result, the resistivity of the obtained silicon single crystal was N-type 3,100 Ω · cm, the oxygen concentration was 0.1 ppma, and the carbon concentration was less than 0.05 ppma.
However, the polycrystalline silicon raw material rod for FZ as described above is expensive and cannot be stably supplied at present.

(Comparative Example 2)
Using a single-crystal manufacturing apparatus shown in FIG. 1 using polycrystalline silicon for FZ having a diameter of 130 mm as a raw material, zoning was performed by the FZ method to manufacture a silicon single crystal having a diameter of 128 mm and a straight body length of about 80 cm. At that time, a dopant gas in which phosphine (PH ₃ ) was diluted to 2.5 ppm with argon was sprayed into the floating zone at a constant rate of 100 cc / min, and gas doping was performed.
At this time, the Ar gas flow rate was 20 l / min, the nitrogen gas concentration in the chamber was 0.5%, the growth rate of the silicon single crystal was 2.0 mm / min, and the eccentricity was 10 mm.

As a result, when N-type polycrystalline silicon for FZ having a resistivity of 4,200 Ω · cm is used as a raw material, the resistivity of the manufactured FZ single crystal silicon is N-type 50.0 Ω · cm as shown in FIG. It was almost uniform in the axial direction. The produced silicon single crystal had an oxygen concentration of 0.1 ppma and a carbon concentration of less than 0.05 ppma.
However, the polycrystalline silicon raw material rod for FZ as described above is expensive and cannot be stably supplied at present.

(Comparative Example 3)
Using the FZ single crystal manufacturing equipment shown in Fig. 1 as the raw material rod, the polycrystalline silicon for FZ with a diameter of 130 mm is used for zoning by the FZ method to manufacture a silicon single crystal with a diameter of 153 mm and a straight body length of about 40 cm without doping. did. The manufactured FZ single crystal silicon was divided into three, and one block was irradiated with neutrons in a nuclear reactor.
At this time, the Ar gas flow rate was 20 l / min, the nitrogen gas concentration in the chamber was 0.5%, the growth rate of the silicon single crystal was 2.0 mm / min, and the eccentricity was 10 mm.

  As a result, when F-type polycrystalline silicon having an N-type resistivity of 4,500 Ω · cm is used as a raw material, the produced neutron-irradiated crystal has an N-type resistivity of 62.8 Ω · cm as shown in FIG. And almost uniform in the axial direction. The produced silicon single crystal had an oxygen concentration of 0.12 ppma and a carbon concentration of less than 0.05 ppma, and the results were almost the same except that the oxygen concentration was slightly lower than that of Example 3.

(Comparative Example 4)
Using a CZ single crystal silicon having a diameter of 130 mm as a raw material rod, zoning was performed by the FZ method using the FZ single crystal manufacturing apparatus shown in FIG. 1, and a silicon single crystal having a diameter of 128 mm and a straight body length of about 80 cm was manufactured. At that time, a dopant gas obtained by diluting phosphine (PH ₃ ) to 0.15 ppm with argon was sprayed to the floating zone at a constant 1,000 cc / min to perform gas doping.
The Ar gas flow rate was 20 l / min, the nitrogen gas concentration in the chamber was 0.5%, the growth rate of the silicon single crystal was 2.0 mm / min, and the eccentricity was 10 mm.

  As a result, N-type CZ single crystal silicon having a cone-side resistivity of 48 Ω · cm and a tail-side resistivity of 20 Ω · cm is used as a raw material. The resistivity was 30 Ω · cm, the resistivity on the tail side was 18 Ω · cm, and the change in resistivity in the axial direction was large.

  The present invention is not limited to the above embodiment. The above embodiment is merely an example, and the present invention has the same configuration as that of 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.

  For example, in the above description, an example has been described with a focus on the case of N-type gas doping using an N-type raw material, but the present invention can also be applied to a case where the raw material is P-type and a P-type dopant is gas-doped. Needless to say.

It is the schematic which shows an example of the single-crystal manufacturing apparatus by FZ method used for this invention. (A) It is a figure which shows the manufacturing flow of the FZ single crystal silicon which used the conventional polycrystalline silicon for FZ as a raw material. (B) It is a figure which shows the manufacture flow of the neutron irradiation FZ single crystal silicon which used the conventional polycrystalline silicon for FZ as a raw material. (A) It is a figure which shows the manufacture flow of the FZ single crystal silicon which used CZ single crystal silicon as a raw material in this invention. (B) It is a figure which shows the manufacture flow of the neutron irradiation FZ single crystal silicon which used CZ single crystal silicon as a raw material in this invention. (A) It is a figure which shows the diameter dispersion | variation of the polycrystalline silicon for FZ. (B) It is a figure which shows the diameter dispersion | variation of CZ single crystal silicon. It is a figure which shows the resistivity of the silicon single crystal after FZ which used CZ single crystal silicon as a raw material. It is a figure which shows the oxygen concentration in the crystal | crystallization of the silicon single crystal before and behind FZ which used CZ single crystal silicon as a raw material. (A) It is a figure which shows the carbon concentration in the CZ single crystal silicon before FZ. (B) It is a figure which shows the carbon concentration in the FZ single crystal silicon after FZ. (A) It is a figure which shows the axial direction resistivity distribution of CZ single crystal silicon before FZ. (B) It is a figure which shows the axial direction resistivity distribution of FZ single crystal silicon after FZ. (A) It is a figure which shows the axial direction resistivity distribution of CZ single crystal silicon before FZ. (B) It is a figure which shows the axial direction resistivity distribution of FZ single crystal silicon after FZ. (C) It is a figure which shows the axial direction resistivity distribution of the single crystal silicon after neutron irradiation. (A) It is a figure which shows the axial direction resistivity distribution of CZ single crystal silicon before FZ. (B) It is a figure which shows an example of the dopant gas flow rate pattern in FZ. (C) It is a figure which shows the axial direction resistivity distribution of FZ single crystal silicon after FZ. It is a figure which shows the resistivity of the single crystal silicon after FZ which used the polycrystalline silicon for FZ as a raw material (comparative example 2). It is a figure which shows the axial direction resistivity distribution of the single crystal silicon after the neutron irradiation which used the polycrystalline silicon for FZ as a raw material.

Explanation of symbols

1 ... CZ silicon crystal rod (silicon raw material rod), 2 ... single crystal rod (silicon single crystal rod),
3 ... Upper shaft, 4 ... Upper holding jig, 5 ... Lower shaft, 6 ... Lower holding jig,
7 ... Induction heating coil, 8 ... Seed crystal, 9 ... Drawing part, 10 ... Floating zone,
11 ... Nozzle for dope gas spraying, 20 ... Chamber,
30: FZ single crystal manufacturing apparatus.

Claims (2)

A silicon single crystal manufacturing method by the FZ method, wherein a P-type or N-type silicon crystal rod having a resistivity of 50 Ω · cm or more manufactured by the CZ method is used as a silicon raw material rod, and the silicon raw material rod is used as the silicon raw material rod The silicon raw material rod is recrystallized into a P-type or N-type silicon single crystal having a desired resistivity by gas doping with impurities having the same conductivity type as the above. A method for producing a silicon single crystal, which is performed by changing a doping gas flow rate in an axial direction according to a direction distribution . 2. The method for producing a silicon single crystal according to claim 1 , wherein a resistivity of the silicon raw material rod produced by the CZ method is 500 Ω · cm or more.

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