WO2004065667A1

WO2004065667A1 - Process for producing single crystal

Info

Publication number: WO2004065667A1
Application number: PCT/JP2003/016795
Authority: WO
Inventors: Ryoji Hoshi; Hiromi Watanabe; Izumi Fusegawa
Original assignee: Shin-Etsu Handotai Co.,Ltd.
Priority date: 2003-01-20
Filing date: 2003-12-25
Publication date: 2004-08-05
Also published as: JP2004224582A

Abstract

A process for producing a single crystal, comprising melting in a crucible a raw material containing at least unwanted portion resulting from single crystal ingots of 0.1 Ωcm or below resistivity pulled up according to the Czochralski method and once more forming a single crystal of 0.1 Ωcm or below resistivity according to the Czochralski method. This technique enables re-utilizing unwanted portion of crystals containing dopant impurities in high proportion which has been inevitably disposed of and enables saving of an expensive metal element required for growing crystals of low resistivity.

Description

Description Single crystal manufacturing method Technical field

The present invention relates to a method for producing a low resistivity crystal and a low resistivity nitrogen-doped crystal which are often used as a substrate for an epitaxy wafer which is manufactured as a high quality single crystal wafer. Background art

Epitaxy wafers are widely used for individual semiconductors and bipolar

It has been used for a long time as an e-ha for manufacturing ICs. MOSLSI is also widely used in microphone-port processor units and flash memory devices because of its excellent soft error and latch-up characteristics. One example of the excellent properties of epitaxial wafers is that there is virtually no so-called row-in defect, which is introduced during the production of single crystals, thus reducing defects such as DRAM reliability. Demand is growing.

In particular, a low resistivity wafer for epitaxy growth, in which the resistivity of the wafer that is the substrate of the epitaxy wafer is 0.1 Ωcm or less, has excellent latch-up characteristics and the substrate The importance of gettering capabilities is increasing. Further, it has been proposed to dope with nitrogen to enhance the gettering ability (see, for example, JP-A-2001-139396).

For the above reasons, the importance of low resistivity crystals and crystals containing many impurities such as nitrogen doped in low resistivity crystals is increasing.

However, when growing low resistivity crystals by the Czochralski method (CZ method), there are specific problems with dopants. For example, when growing a P-type low-resistivity crystal, elements such as metal boron are consumed in large quantities, but it is difficult to obtain a high-purity one, and if the purity is high, it becomes very expensive. And the cost of crystal production is increased. As an attempt to reduce the raw material cost, in the case of ordinary resistivity crystals with a resistivity greater than 0.1 Ωcm, the particle monitor is reused by reusing the cone and tail of the nitrogen-doped crystal. It has been proposed to use it as a wafer

0 0 1-3 3 2 5 9).

In the case of crystals with normal resistivity, cones and tails that do not satisfy the standard diameter of the grown crystal, and where the standard diameter is satisfied, there are slips or parts that do not meet the resistivity standard For example, it has been proposed to reuse parts that cannot be processed into silicon wafers as raw materials for solar cells and the like (see, for example, Japanese Patent Application Laid-Open No. 2002-108497).

When the resistivity was not so low as described above, the wafer could be reused as a wafer for particle monitors and an wafer for solar cells. However, low-resistivity crystals of 0.1 Qcm or less and crystals further doped with nitrogen are crystals used for specific applications and contain many dopant impurities. When used for particle monitors, solar cells, etc., the electrical and defect characteristics change, which makes it difficult to reuse and has to be disposed of.

In such a crystal containing a large amount of impurities, a cone portion that is less than the standard diameter, a tail portion, a crystal defect such as a slip or OSF even if the standard diameter is satisfied, or a resistivity standard or There was a problem in reusing so-called unnecessary parts, such as parts that do not meet quality requirements, such as being out of the oxygen concentration standard. Disclosure of the invention

The present invention has been made in view of such a problem, and is intended to reuse an unnecessary portion of a low-resistance crystal containing a large amount of dopant impurities, which had to be discarded in the past, and to grow a low-resistance crystal. The main purpose is to provide a technology that can reduce the cost of producing these crystals and also provide an environment-friendly crystal production method by providing technologies that can save the necessary expensive metal elements. .

The present invention for solving the above-mentioned problems is directed to a method for producing a single crystal, which comprises at least a single crystal having a resistivity of 0.1 Ωcm or less pulled by the Cjochralski method. This is a method for producing a single crystal, characterized by melting a raw material containing an unnecessary portion derived from an ingot with a crucible and again producing a single crystal having a resistivity of 0.1 Ωcm or less by the Czochralski method.

In this way, unnecessary portions derived from a low-resistivity single-crystal ingot containing a large amount of dopant and having a resistivity of 0.1 Ωcm or less are again subjected to the Czochralski method to a low-resistance single-crystal having a resistivity of 0.1 Ωcm or less. By using it as a raw material for producing crystals, the raw material can be reused.

In this case, the unnecessary portion is a portion having a cone portion, a tail portion, a slip dislocation, a portion having an OSF or a crystal defect, or a resistivity standard out of a single crystal ingot pulled up by the Czochralski method. At least one part, which does not satisfy the oxygen concentration standard, can be used.

In this way, low-resistivity crystals can be reused by reusing low-resistivity crystal cones, etc., which were conventionally difficult to recycle and had to be disposed of, as raw materials for low-resistivity crystals. The cost of crystal production can be reduced.

In this case, when the unnecessary portion is melted with a crucible as a raw material, it can be used alone or mixed with an unused polycrystalline raw material to reduce the amount of depant used to control the resistivity. It can be.

In this way, by controlling only the unnecessary portion derived from the already manufactured single crystal ingot, or by mixing the unnecessary portion with the unused polycrystalline raw material, the resistivity of the single crystal to be manufactured again is controlled, A single crystal having a desired resistivity can be obtained, and the amount of expensive dopant can be reduced.

In this case, the single crystal ingot pulled up by the Czochralski method from which the unnecessary portion is derived is preferably a single crystal doped with polon.

In this way, if the single crystal ingot from which the unnecessary portion is derived is doped with boron, boron has a large segregation coefficient of about 0.8, so that most of the boron in the raw material that melts this unnecessary portion Will be re-introduced into the low resistivity crystal to be remanufactured. Therefore, it is possible to save expensive boron elements. In this case, the single-crystal ingot pulled up by the Czochralski method from which the unnecessary portion is derived can be a single crystal doped with nitrogen. As described above, in the case of a single crystal ingot obtained by further doping nitrogen into a low resistivity crystal, an unnecessary portion derived from the crystal can be used again as a raw material for a low resistivity nitrogen doped crystal. In the case of nitrogen, the segregation coefficient is very small, 0.0007, so even if an unnecessary portion of the nitrogen-doped crystal is used again as a raw material for the nitrogen-doped crystal, it hardly affects the target nitrogen doping concentration. This has the advantage that no adjustment is required for the nitrogen concentration.

In this case, it is preferable that the single crystal ingot pulled up by the Czochralski method from which the unnecessary portion is derived has a nitrogen concentration of 1 × ^{10 10} to 5 × ¹⁰ ¹⁵ / cm ³ .

This is because a nitrogen concentration of ¹ × 10 ^{1 Q} pieces Z cm ³ or more is required to control crystal defects, and a concentration that does not hinder single crystallization is 5 × 10 ¹⁵ pieces / cm ³ Therefore, the nitrogen-doped crystal often has such a nitrogen concentration, and such a concentration does not adversely affect the crystal to be manufactured again.

In this case, it is preferable that the single-crystal ingot or the polycrystalline raw material drawn by the Czochralski method from which the unnecessary portion is derived is silicon. If the single crystal ingot from which the unnecessary portion is derived and the polycrystalline raw material mixed with the single crystal ingot are silicon, for example, a silicon single crystal produced from the unnecessary portion may be used as a substrate for an epitaxial wafer or a high gettering substrate. Thus, it can be used as a substrate for a semiconductor integrated circuit.

As described above, the method for producing a single crystal of the present invention is intended to reuse an unnecessary portion of a crystal which had to be discarded because it contains a lot of impurities, and to grow a low resistivity crystal. By providing a technology that can save the necessary expensive metal elements, it is possible to not only reduce the cost of producing these crystals, but also to provide an environmentally friendly crystal production method. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a flowchart showing the manufacturing method of the present invention.

FIG. 2 schematically shows a single crystal growing apparatus and HZ that can be used in the method of the present invention. FIG.

FIG. 3 is a diagram showing the results of measuring the resistivity axial distribution of a single crystal in the case of an unused raw material and in the case of a recycled raw material.

Fig. 4 is a diagram showing the required amount of metal polon elements with respect to the resistivity of the raw material and the target resistivity.

FIG. 5 is a diagram showing a calculated nitrogen concentration axial distribution.

FIG. 6 is a diagram showing the measurement results of nitrogen concentration by SIMS in the case of an unused raw material and in the case of a recycled raw material.

Figure 7 is a diagram comparing the calculated values of nitrogen concentration in the case of unused raw materials and the case of recycled raw materials. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail.

As mentioned above, there has been a problem in the past in terms of reusing raw materials for low resistivity crystals. This is because, in the past, unnecessary parts derived from low-resistivity crystal ingots were to be reused for manufacturing particle monitors, solar cells, and solar cells, similar to ordinary resistivity crystals. is there. Unnecessary parts of crystals containing a large amount of dopant impurities are not easy to reuse as raw materials for particle monitors, solar cells, solar cells, etc. from the viewpoint of controlling electrical and defect characteristics. Of course, it cannot be reused as a crystal material with normal resistivity that is usually grown, because it also poses a major problem in controlling electrical and defect properties.

Therefore, the present inventors have for the first time conceived the idea of reusing the unnecessary portion of a crystal containing a large amount of dopant impurities as a raw material for a low resistivity crystal containing a large amount of the same dopant impurity. did. With this method, unlike in the case of reusing as a crystal family with normal resistivity, the change in the electrical and defect characteristics of the crystal manufactured from the recycled material is small, so that it can be reused. . Even if unnecessary parts of the crystal ingot containing more dopant than necessary are reused, there is a segregation phenomenon during crystal growth, so a certain percentage of the raw material melt containing impurities is used. It has the characteristic that it is not incorporated into the crystal only if it is. Therefore, by utilizing this phenomenon, even if an unnecessary portion containing a large amount of dopant impurities is melted, only a part of the portion is taken into the crystal to be remanufactured, and as a low resistivity crystal having a desired resistivity, It can be reused.

On the other hand, the present invention is effective even when an unnecessary portion of a crystal ingot containing a smaller amount of dopant impurities than necessary is reused. As described above, segregation occurs during crystal growth, and only a certain percentage of the dopant contained in the melt is incorporated into the crystal. This ratio is the segregation coefficient. However, for example, in a P-type low resistivity crystal, boron is used as a dopant, but its segregation coefficient is relatively large, about 0.8. Therefore, unnecessary portions of the boron-doped low-resistivity crystal are incorporated into the crystal to be remanufactured by a large amount of boron contained in the molten raw material. As a result, the amount of boron that must be added to re-manufacture a crystal having the required resistivity is significantly reduced, and it is possible to save expensive metal por- tion elements.

In this way, when controlling the resistivity of the low-resistivity crystal, the unnecessary portion of the low-resistivity crystal ingot is used again as a raw material for the low-resistivity crystal, thereby reducing the amount of dopant to be supplied. It is possible to do.

As described above, it is very effective to reuse unnecessary parts derived from low-resistivity crystal ingots again as raw materials for low-resistivity crystals in terms of the properties of recrystallized crystals and saving of raw materials. It is.

Also, when the unnecessary portion of the low resistivity crystal is reused as a raw material for the low resistivity crystal again, not only the unnecessary portion obtained from the low resistivity crystal but also the unused pure polycrystal are used. A desired resistivity can be aimed at by mixing and using the raw materials. For example, if a crystal is grown again from raw material obtained only from the tail of a crystal ingot with a certain resistivity, the resistivity of the remanufactured crystal may be lower than that of the original crystal. There is. Therefore, a desired resistivity can be obtained by mixing unused pure polycrystalline raw materials with unnecessary portions of the low-resistivity crystal. Is 0.001. ^ From 0.1 Ω cm. This is because it is difficult to form a single crystal at a resistivity of less than 0.01 Ωcm, and the effect of element saving is small at a resistivity of more than 0.1 Ωcm. Further, if an unnecessary portion of a crystal ingot of 0.1 Ωcm or less is reused as a material for a crystal having a normal resistivity or a particle monitor, the electrical characteristics and defect characteristics are greatly changed. When reusing an unnecessary portion of a crystal of l Q cm or less, it is preferable to use the crystal as a raw material for a low resistivity crystal of 0.1 Ω cm or less again.

Further, in the case of a crystal obtained by further doping nitrogen into a low-resistivity crystal, an unnecessary portion obtained from the crystal can be used as a raw material for a low-resistivity nitrogen-doped crystal. In the case of nitrogen, the segregation coefficient is very small, 0.0007, so even if an unnecessary portion of the nitrogen-doped crystal is used again as a raw material for the nitrogen-doped crystal, the nitrogen-doped crystal has almost no effect on the target nitrogen doping concentration The advantage is that it has no effect.

In other words, with regard to the nitrogen concentration, no consideration is required at all, such as adjusting the dopant amount as in the resistivity control by the dopant or adding an unused pure polycrystalline raw material. Therefore, when the unnecessary portion of the nitrogen-doped low resistivity crystal is reused for the nitrogen-doped low resistivity crystal, there is no need to adjust the nitrogen concentration at all. Hereinafter, the present invention will be described more specifically, but the present invention is not limited thereto.

FIG. 1 is a flowchart showing the manufacturing method of the present invention. First, a single crystal ingot 1 with a resistivity of 0.1 Ω cm or less is pulled up by the Chiyoklarski method. When the straight body part 2 as a product is taken out of the single crystal ingot 1, a cone part 3 and a tail part 4, which are unnecessary parts 10, are derived (Fig. 1 (a)). In addition, unnecessary portions 10, such as portions having slip dislocations, OSFs and crystal defects, portions not meeting the resistivity standard, and portions not meeting the oxygen concentration standard, are derived from the single crystal ingot 1. I do.

Next, these unnecessary portions are melted in a crucible 5 to obtain again a raw material melt 6 for producing a single crystal having a resistivity of less than 0.1 ΩΩοηι (FIG. 1 (b)). At this time, unused polycrystalline raw material 7 and metal elements (boron, phosphorus, antimony, etc.) can be added, mixed, and melted so as to obtain a target low resistivity.

Then, using the raw material melt 6, the resistivity is again determined using the Chiyoklarski method. A single crystal ingot 11 of 0.1 Ωcm or less is manufactured (Fig. 1 (c)). From the remanufactured single crystal ingot 11, if the straight body part 12 as a product is taken out, unnecessary parts 20 such as a cone part 13 and a tail part 14 are derived, but this unnecessary part 20 By repeating the above steps, the raw materials can be reused.

It should be noted that a step such as washing may be added between the above steps due to manufacturing reasons.

When a single crystal ingot is manufactured by the Czochralski method, for example, the single crystal growing apparatus shown in FIG. 2 can be used. In this single crystal growing apparatus 30, a crucible 35 is provided in a champ 32 into which a hot zone (H Z) is inserted, and a heater 33 surrounding the crucible 35 is provided. The raw material containing the unnecessary portion of the low resistivity crystal ingot is put into the crucible 35 and is heated and melted by the heater 33 to obtain a raw material melt 36. At this time, the unused polycrystalline raw material and the metal element are adjusted and melted as necessary so that the target low resistivity is obtained. After immersing seed crystal 34 in the liquid surface of melt 36 in crucible 35, rod-shaped single crystal 31 is pulled out of the melt. The crucible 35 can move up and down in the direction of the crystal growth axis, and raises the crucible 35 so as to capture the lowering of the liquid level of the melt that has crystallized and decreased during the crystal growth. Thereby, the height of the surface of the melt 36 is always kept constant. In this case, the MCZ method in which a magnetic field is applied to the raw material melt 36 may be used.

The manufactured single crystal 31 is inspected to see if its quality such as slip, OSF, resistivity, oxygen concentration, etc. meets the requirements. The tail portion is reused as a raw material for the low resistivity crystal as described above. Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited thereto.

(Example 1)

The hot zone of the single-crystal growth apparatus using the Czochralski method whose schematic diagram is shown in Fig. 2 is equipped with a crucible having a diameter of 32 inches (800 mm) and a diameter of 12 inches (300 mm). ) Silicon single crystal was grown. Unused pure polycrystalline silicon raw material 3 Charged 20 kg crucible. From this crucible, a 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 350 G. At this time, the metal polon element was doped so that the resistivity was 0.008 Qcm at the position of the straight body length O cm (crystal shoulder) of the crystal.

A sample in the form of a wafer was taken from the crystal every 25 c Hi, and the resistivity was measured. As a result, as shown in Fig. 3, the resistivity decreases in the length direction of the crystal, and a crystal with a straight body length of about 120 cm (120 cm from the shoulder) and a thickness of 0.06 Q cm is formed. Obtained. Next, the cone part, tail part and regular diameter that are less than the regular diameter of the low-resistivity crystal are satisfied so that the average resistivity of the recycled material is 0.0129 Qcm. Even if it was used, 320 kg of parts that had crystal defects such as slips or did not meet the quality requirements were collected, crushed to a size that could be used as a raw material, and washed. . Then, using the single crystal growing apparatus used above, a horizontal magnetic field with a center magnetic field strength of 350 G was applied, and a straight body length of about 120 cm and a diameter of 320 kg of the recycled material were obtained. Two 12-inch (300 mm) silicon single crystals were grown again. At this time, a metal boron element was added so that the resistivity became 0.08 Ωcm for the crystal of 0 cm.

Here, in the case of boron, its segregation coefficient is relatively large, about 0.8. Therefore, boron contained in the raw material melt efficiently enters the crystal to be remanufactured. Therefore, when a recycled material prepared from a low resistivity crystal is used, the metal boron element can be saved.

Fig. 4 shows what percentage of the metal polon should be added when the ratio of the resistivity of the raw material to the target resistivity is used and pure unused raw material is used. In the case of the first embodiment, the resistivity of the raw material obtained by reusing the unnecessary portion is 0.012 Qcm, whereas the target resistivity is 0.008 Ωcm, and the ratio is 0.02 Qcm. 0 1 2 9/0. 0 0 8 = 1.6 1 2 5 Therefore, from Fig. 4, it is clear that about 58% of the metal boron element in the case of using a pure unused raw material should be introduced. In other words, the savings in metal boron elements can be as much as 42%.

Then, the resistivity of the actually remanufactured single crystal was measured in the same manner as for the single crystal manufactured from the unused raw material described above, and as shown by the solid line in FIG. The silicon single crystal re-manufactured from unnecessary parts in 1 had a resistivity distribution equivalent to that of unused raw materials, and was resistant to reuse.

(Example 2)

Next, unnecessary parts were collected from the same silicon crystal as the crystal grown in Example 1, and this was ground into a size that could be used as a raw material, and washed. Approximately 85% of the 320 kg raw material was recycled from this unnecessary portion, and the remaining 15% was made from pure unused polycrystal. Using these raw materials, a horizontal magnetic field having a central magnetic field strength of 350 G was applied using the single crystal growing apparatus used in Example 1 to obtain a straight body length of about 120 cm and a diameter of 12 inches. Two (300 mm) silicon single crystals were grown again. At this time, the metal boron element was not doped. Therefore, the amount of saving of the metal porous element in the second embodiment is 100%.

Then, the resistivity of the actually remanufactured single crystal was measured in the same manner as for the single crystal manufactured from the above-mentioned unused raw material. As shown by the broken line in FIG. The silicon single crystal remanufactured from Japan also had a resistivity distribution equivalent to that using unused raw materials, and was resistant to reuse.

As described above, the unnecessary portion derived from the low resistivity crystal ingot can be used as a raw material for low resistivity crystallization. The segregation coefficient of boron is relatively large, about 0.8. Therefore, the boron contained in the raw material obtained by melting the unnecessary portion obtained from the low resistivity crystal is incorporated into the single crystal to be re-manufactured, thereby saving expensive metal boron elements. It becomes possible. At this time, in some cases, a desired resistivity can be obtained by mixing unused pure materials. (Experiment)

Next, an experiment was conducted to investigate the effect of using the unnecessary part of the nitrogen-doped crystal again as a raw material for the nitrogen-doped crystal. Since the nitrogen concentration cannot be investigated with low resistivity crystals, this experiment was performed with normal resistivity crystals of 10 Ωcm or more. Using the single crystal growing apparatus used in Example 1 and Example 2, the central magnetic field strength 3 5 A horizontal magnetic field of 0 G is applied, and 320 kg of unused pure polycrystalline raw material is used to produce a silicon with a straight body length of about 120 cm and a diameter of 12 inches (300 HI m). Single crystals were grown. At this time, nitrogen was doped by charging the silicon wafer with the nitride film together with the raw materials into the crucible. The target nitrogen concentration was 3 × 10 ¹³ cm ³ at the straight body portion O cm of the crystal. In the case of nitrogen, the segregation coefficient is as small as 0.0007. Therefore, the calculated nitrogen concentration in the above crystal becomes as shown in Fig. 5, and it increases with the length of the cylinder.

A sample was taken from a portion near the boundary between the tail portion and the straight body portion of the crystal, and the nitrogen concentration was measured by SIMS. Four samples taken from four similar crystals were used for the measurement. As a result, as shown in FIG. 6, the average value of the nitrogen concentration was approximately 1.2 × 10 ¹⁴ Z cm ³ . This compares with calculated values 1. 0 X 1 0 ¹⁴ atoms Z cm ³ at sampling portion shown in FIG. 5, when considering from the nitrogen concentration measurement accuracy of SIMS, and it is the nitrogen doping as aimed You can see that.

The crystal properties other than nitrogen concentration, such as oxygen concentration, OSF, lifetime, and FPD (Grown-in defect) were also investigated.

Next, the cone and tail portions of the crystal ingot grown as described above were collected, crushed to a size that could be used as a raw material, and washed. Except that this was collected for 32 O kg and this recycled material was used as a raw material, the straight body length was about 120 c under exactly the same conditions as when it was manufactured from the above-mentioned unused raw material. _m, were grown silicon single crystal having a diameter of 1 2 I inch (3 0 0 mm).

Here if, among the crystal Ingo' bets were grown in the above-mentioned unused raw material, portion having the highest concentration of nitrogen tail destination end (:. ~ 1 2 X 1 0 14 atoms Z cm ³⁾ only 3 2 0 kg When they were collected and the crystal was grown again, the nitrogen concentration was calculated. Fig. 7 shows the calculated values of the nitrogen concentration at a straight body of 0 cm and a straight body of 120 cm in the case of unused raw materials and the case of recycled raw materials. As mentioned above, the segregation coefficient of nitrogen is very small, so the difference between unused and recycled materials is 0.3. /. It turns out that it is very small within.

Then, a sample was taken from the part near the boundary between the tail part and the straight body part of the crystal actually grown from the recycled material, and the nitrogen concentration was measured by SIMS. Was compared with the value. As a result, as shown in Fig. 6, The concentration was 1.1 × 10 ¹⁴ Z cm ³ . This can be said to be the same concentration as crystals produced from unused raw materials, taking into account the measurement accuracy of SIMS.

Oxygen concentration, OSF, lifetime, and FPD (Grown-in defect) characteristics were investigated as crystal characteristics other than nitrogen concentration, and all showed the same characteristics as crystals manufactured from unused raw materials. .

As described above, the unnecessary portion obtained from the nitrogen-doped crystal can be used again as a raw material for the nitrogen-doped crystal. In the case of nitrogen, the segregation coefficient is very small, 0.0007, so even if an unnecessary portion of the nitrogen-doped crystal is used again as a raw material for the nitrogen-doped crystal, the nitrogen-doped crystal will almost never reach the target nitrogen doping concentration. Has no effect.

Although the above experiment was performed using a crystal having a normal resistivity for measurement, substantially the same result is expected to be obtained with a crystal having a low resistivity of 0.1 Ω cm or less. Therefore, it means that the unnecessary portion derived from the crystal ingot obtained by further doping the low resistivity crystal with nitrogen can be used again as a raw material of the low resistivity nitrogen doped crystal. Note that the present invention is not limited to the above embodiment. The above embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the claims of the present invention. It is included in the technical scope of the invention.

For example, in the above embodiment of the present invention, a silicon single crystal having a diameter of 12 inches (300 mm) to which a horizontal magnetic field is applied has been described. However, this reused material is not affected by the presence or absence of a magnetic field, the crystal diameter, and the type of dopant, and is not limited to a low resistivity crystal of 0.1 Ωcm or less. Application is possible. Accordingly, the gist of the present invention is that "a crystal part containing a large amount of dopant impurities, such as a cone part, a tail part, or a crystal defect such as a slip even though the diameter is satisfied, is less than the predetermined diameter. Unnecessary parts, such as parts whose quality deviates from resistivity standards and oxygen concentration standards and do not satisfy requirements, are used again as a raw material for crystals containing a large amount of dopant impurities '' are within the scope of the present invention. Included.

Claims

The scope of the claims

1. A method for producing single crystals, in which a crucible is used to melt the raw material containing unnecessary parts derived from a single crystal ingot with a resistivity of 0.1 Ωcm or less, which is raised at least by the Cjochralski method. And producing a single crystal having a resistivity of 0.1 Qcm or less again by the Chiyoklarski method.

2. The unnecessary portion is a portion of the single crystal ingot pulled up by the Czochralski method, which has a cone portion, a tail portion, a slip dislocation, an OSF or a crystal defect, and does not satisfy a resistivity standard. 2. The method for producing a single crystal according to claim 1, wherein the portion is at least one portion that does not satisfy the oxygen concentration standard.

3. When the unnecessary portion is melted in a crucible as a raw material, the amount of dopant to control the resistivity can be reduced by using it alone or by mixing it with an unused polycrystalline raw material. 3. The method for producing a single crystal according to claim 1 or 2, wherein:

4. The method according to any one of claims 1 to 3, wherein the single crystal ingot pulled by the Czochralski method from which the unnecessary portion is derived is a single crystal doped with boron. The method for producing a single crystal according to the above.

5. The single crystal ingot pulled by the Czochralski method from which the unnecessary portion is derived is a single crystal doped with nitrogen, wherein the single crystal ingot is a single crystal doped with nitrogen. 13. The method for producing a single crystal according to the above item.

6. The nitrogen concentration of the single crystal ingot pulled up by the Czochralski method from which the unnecessary portion is derived is 1 × ^{10 10} to 5 × ¹⁰ ¹⁵ Z c in ^3. 6. The method for producing a single crystal according to 5.

^{7. The} single crystal ingot or the polycrystalline raw material pulled up by the Czochralski method from which the unnecessary portion is derived is silicon, wherein the raw material is silicon. 3. The method for producing a single crystal according to item 1.