JP2011093778A - Silicon single crystal wafer and method for producing silicon single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a silicon single crystal which is suitable for a power device or the like needing high pressure resistance and is suited for production of a large-diameter silicon single crystal scarcely including oxygen, and to provide a silicon single crystal wafer. <P>SOLUTION: There are provided a silicon single crystal wafer which is grown by the Czochralski method, has an oxygen concentration of ≤1×10<SP>17</SP>atoms/cm<SP>3</SP>(ASTM'79) and has an in-plane distribution of electric resistivity of ≤10%, and a method for producing the silicon single crystal. The method is characterized by using for holding at least a raw material melt, a crucible which is composed of a material having a higher melting point than silicon and containing no oxygen atom in composition, and by applying a magnetic field for suppressing the convection of the raw material melt when a silicon single crystal is withdrawn from a raw melt by the Czochralski method. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a silicon single crystal wafer and a method for producing a silicon single crystal, and more specifically, to a method for producing a silicon single crystal by the Czochralski method that contains almost no oxygen in the wafer and a silicon single crystal wafer.

There are two main methods for producing a silicon single crystal, the Czochralski method (hereinafter also referred to as CZ method) and the FZ method.
Of these, CZ crystals obtained by the CZ method are widely used in memory devices and the like.

Here, in the CZ method, a quartz crucible is usually used as a crucible for directly holding the raw material melt. For this reason, oxygen elutes from the quartz crucible and is taken into the silicon single crystal through the silicon raw material melt.
Therefore, the CZ silicon single crystal wafer is characterized in that it always contains oxygen. In such a wafer containing oxygen, mechanical strength increases or oxygen forms a precipitate (BMD: Bulk Micro Defect). They exhibit excellent properties such as gettering heavy metal impurities that come in as contaminants during the device process.
Thus, CZ crystals have been used in many devices because of the advantage based on containing a large amount of oxygen.

On the other hand, FZ crystals not containing oxygen are widely used for wafers required for power devices and the like that require high breakdown voltage.
This is because power devices and the like require high breakdown voltage characteristics, and there is a concern that a high breakdown voltage cannot be obtained in a wafer that contains a large amount of oxygen like conventional CZ crystals and forms precipitates. It was.
In addition, since the temperature gradient is very large in the FZ crystal, the size of grown-in defects formed by agglomeration of point defects is small, and since there is no oxygen, COP (Crystal Originated Particles) like the CZ crystal. = Vacancy type point defect agglomerates) and the like are not formed on the inner wall. For this reason, a grown-in defect is not seen only by doping with nitrogen, and it is suitable for obtaining a wafer suitable for high withstand voltage.

JP 59-35094 A JP-A-9-221379 Japanese Patent Laid-Open No. 9-221380 JP-A-5-155682

Fukuda, Yoshio & Hikawa, Satoshi, “Single Crystal Growth Technology to Support Modern Electronics”, Chapter 2.3, Baifukan

  However, the FZ method has a problem that it is difficult to increase the diameter of 8 inches or more, and it is very difficult to obtain a large diameter crystal of 200 mm or more that does not contain oxygen.

Regarding the technology for growing a silicon single crystal with a material that does not contain oxygen in the composition, that is, a crucible without an oxygen supply source, for example, Patent Documents 1, 2, and 3 disclose a crucible made of a material such as silicon nitride or silicon carbide. Has been described and was once done.
However, in a wafer manufactured from a silicon single crystal that does not contain oxygen, there is a problem that slip resistance and gettering ability cannot be obtained, and as in Patent Document 1 in which silicon oxide is brought into contact with the raw material melt, rather oxygen is used. Techniques for adding have been studied.
Therefore, a substantially oxygen-free CZ crystal could not be produced.

  In addition, when a crucible without an oxygen supply source was studied in the past, such as Patent Document 1 described above, the diameter of the single crystal to be pulled is small, and the problem of convection of the raw material melt is almost regarded as a problem. There was no. Therefore, there was no technique for applying a magnetic field to a crucible without an oxygen supply source.

On the other hand, as described in Non-Patent Document 1 and the like, it is known that the MCZ method in which a magnetic field is applied can reduce the oxygen concentration by increasing the magnetic field strength. For this reason, a technique for applying a magnetic field for reducing oxygen concentration as disclosed in Patent Document 4 is disclosed.
In this sense, the MCZ method characterized in that the oxygen concentration can be reduced even when a quartz crucible is used, and the idea of using a crucible without an oxygen supply source was not in the first place.

  The present invention has been made in view of the above problems, and is suitable for a power device that requires a high breakdown voltage, and is suitable for producing a large-diameter silicon single crystal containing almost no oxygen. It is an object to provide a manufacturing method and a silicon single crystal wafer.

In order to solve the above problems, the present invention provides a silicon single crystal wafer grown by the Czochralski method, and the silicon single crystal wafer has an oxygen concentration of 1 × 10 ¹⁷ atoms / cm ³ (ASTM 79) or less. And a resistivity in-plane distribution is within 10%.

Thus, in the present invention, a silicon single crystal wafer grown by the Czochralski method having an oxygen concentration of 1 × 10 ¹⁷ atoms / cm ³ (ASTM 79) or less and a resistivity in-plane distribution of 10% or less. I will provide a.
Such a silicon single crystal wafer has a very low oxygen content in the wafer and does not substantially contain it, and is suitable for a wafer requiring a high breakdown voltage such as a power device.
In addition, since it is obtained from a single crystal grown by the Czochralski method, the resistivity within the wafer surface, especially the resistivity in-plane distribution (the difference between the maximum value and the minimum value within the wafer surface is minimized) (Value divided by the value) is within 10% and is a uniform wafer, which is suitable for device manufacturing.
Furthermore, since the wafer is grown by the Czochralski method, for example, a large-diameter wafer having a diameter of 200 mm or more that is difficult to manufacture by the FZ method can be obtained. In other words, it fully meets the demand for larger diameters of single crystal wafers in order to meet the recent demands for higher integration and higher precision of semiconductor devices.

  Further, the present invention is a method for producing a silicon single crystal, and when the silicon single crystal is pulled up from the raw material melt by the Czochralski method, at least the crucible holding the raw material melt has a higher melting point than silicon. Provided is a method for producing a silicon single crystal, characterized by using a crucible composed of a material not containing oxygen atoms in its composition and applying a magnetic field for suppressing convection of the raw material melt.

As described above, when pulling up the silicon single crystal by the Czochralski method, the crucible for holding the raw material melt is made of a material having a higher melting point than silicon and containing no oxygen atoms in the composition. During the pulling of the crystal, a magnetic field for suppressing convection of the raw material melt is applied.
As a result, it is possible to prevent the oxygen derived from the crucible from being taken into the silicon single crystal, which could not be avoided in the case of the CZ method using a quartz crucible for holding the raw material melt as in the prior art. Therefore, a silicon single crystal suitable for cutting out a silicon single crystal wafer suitable for a power device or the like that is required to have a low oxygen content can be easily produced.
Moreover, since it is manufactured by the Czochralski method, it is easy to increase the diameter. For example, it is possible to easily obtain a silicon single crystal having a diameter of 200 mm or more, which is difficult by the FZ method.
Furthermore, by applying a magnetic field, the large-diameter silicon single crystal is pulled up, that is, the convection of the raw material melt, which becomes more problematic as the large-diameter crucible is used, can be suppressed, and the silicon single crystal cannot be pulled up. It can be prevented from happening. Therefore, the production yield and quality can be improved.

Here, it is preferable to use any one of carbon, silicon carbide, silicon nitride, boron nitride (PBN), tungsten, molybdenum, and niobium as the material of the crucible.
As described above, any material of carbon, silicon carbide, silicon nitride, boron nitride (PBN), tungsten, molybdenum, and niobium does not contain oxygen and is stable at a melting point of silicon of about 1400 ° C. or higher. A crucible having a size capable of growing a crystal of 200 mm or more can be easily formed. Therefore, it is suitable as a material having a melting point higher than that of silicon and containing no oxygen atoms in the composition.

Moreover, it is preferable that the intensity | strength in the center part on the solid-liquid interface of the said silicon single crystal being pulled is 500 Gauss or more and 6000 Gauss or less.
Thus, the effect of suppressing crucible convection for growing a single crystal having a large diameter of 200 mm or more by setting the strength of the magnetic field at the central portion on the solid-liquid interface of the silicon single crystal being pulled to 500 Gauss or more. Can be large.
Moreover, by setting it as 6000 Gauss or less, it is not necessary to enlarge the apparatus which generate | occur | produces a high magnetic field, and it can prevent that the problem that the problem of a leakage magnetic field and a cost become high generate | occur | produces.
Furthermore, for the same reason that the supply of oxygen from the quartz crucible can be reduced by applying the magnetic field shown in Non-Patent Document 1 and Patent Document 4, it is possible to suppress the dissolution of the crucible components by applying the magnetic field. be able to. For this reason, for example, even when a carbon crucible is used, a crystal having a low carbon concentration can be obtained.

Then, when pulling up the silicon single crystal, the in-plane distribution of the temperature gradient G in the vicinity of the growth interface and the pulling speed V of the silicon single crystal are controlled by adjusting the in-furnace structure, so that the silicon single crystal to be pulled up is controlled. It is preferable to control V / G so that a defect-free region is generated in the crystal.
Thus, by using the temperature gradient G in the furnace and an appropriate growth rate V, a silicon single crystal having no grown-in defects can be grown. Therefore, it is possible to manufacture a silicon single crystal that can cut out a silicon single crystal wafer that contains almost no oxygen and has no grown-in defects, that is, an extremely low oxygen and defect-free silicon single crystal wafer.

Furthermore, it is preferable that the diameter of the silicon single crystal to be pulled is 200 mm or more.
Thus, even if the diameter of the single crystal to be pulled is 200 mm or more, the Czochralski method can be easily grown and the diameter can be easily increased.

Furthermore, the present invention provides a silicon single crystal wafer characterized by being obtained by slicing a silicon single crystal manufactured by the method for manufacturing a silicon single crystal according to the present invention.
As described above, the method for producing a silicon single crystal according to the present invention can easily obtain a large-diameter silicon single crystal containing substantially no oxygen concentration and having a uniform in-plane resistivity distribution. It can be done. Therefore, a silicon single crystal wafer obtained by slicing a silicon single crystal manufactured by such a method for manufacturing a silicon single crystal also has an extremely low oxygen concentration and a uniform resistivity distribution in the wafer surface. ing.

  As described above, according to the present invention, a method for producing a silicon single crystal suitable for producing a large-diameter silicon single crystal containing almost no oxygen, which is suitable for a power device requiring high breakdown voltage, and the like. A silicon single crystal wafer is provided.

It is the figure which showed an example of the outline of the silicon single crystal growth apparatus which can be used with the manufacturing method of the silicon single crystal of this invention. It is the graph which showed the evaluation result of the in-plane distribution of the resistivity of the silicon single crystal wafer obtained in Example 1 of this invention. It is explanatory drawing showing the relationship between V / G and crystal defect distribution. It is the figure which showed an example of the outline of the silicon single crystal growth apparatus used with the manufacturing method of the conventional silicon single crystal.

Hereinafter, the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.
The silicon single crystal wafer of the present invention is grown by the Czochralski method, the oxygen concentration in the wafer is 1 × 10 ¹⁷ atoms / cm ³ (ASTM 79) or less, and the resistivity surface in the wafer surface This is a wafer having an internal distribution within 10%.

Thus, if the oxygen concentration in the wafer is 1 × 10 ¹⁷ atoms / cm ³ (ASTM 79) or less, the oxygen content is very low and a silicon single crystal wafer in which precipitates are hardly formed is obtained. Therefore, it is suitable for power device applications requiring high breakdown voltage.
In addition, in the CZ crystal grown by the Czochralski method, the in-plane uniformity of resistivity is generally superior to that of the FZ crystal, and the ratio of the central portion to the peripheral portion (for example, 5 mm from the edge) is 10 % Wafers can be easily manufactured. Therefore, in the FZ crystal, neutron irradiation may be performed in order to maintain the uniformity of the in-plane resistivity, but there is a merit that it is not necessary to perform such a high-cost process. Become.
Furthermore, since it is produced from a silicon single crystal wafer grown by the Czochralski method, a large diameter having a diameter of 200 mm or more, further 300 mm or more can be easily obtained.

  The silicon single crystal wafer of the present invention as described above can be produced by cutting from a silicon single crystal produced by the method for producing a silicon single crystal of the present invention as described below. One example is shown below, but the present invention is not limited to these.

In describing the silicon single crystal manufacturing method of the present invention, first, an example of a silicon single crystal growing apparatus used in the silicon single crystal manufacturing method of the present invention will be described with reference to FIG. .
FIG. 1 is a diagram showing an example of an outline of a silicon single crystal growing apparatus that can be used in the method for producing a silicon single crystal of the present invention.

1 includes a crucible 6 filled with a raw material melt 4, a heater 7 and a heat insulating member 8 arranged so as to surround the crucible 6, and are installed in the main chamber 1. A pulling chamber 2 for accommodating and taking out the grown silicon single crystal 3 is connected to the upper portion of the main chamber 1.
Further, the single crystal growing device 16 is arranged such that a coil (magnetic field generating coil) constituting an electromagnet of the magnetic field applying device 15 is disposed coaxially opposite to the outside of the main chamber 1 with the crucible 6 interposed therebetween, and the raw material in the crucible 6 In this structure, a horizontal magnetic field can be applied to the melt 4.

  When the silicon single crystal 3 is grown using such a single crystal growing apparatus, the seed crystal 5 is immersed in the raw material melt 4 in the crucible 6 by the Czochralski method (CZ method), and then the seed drawing is performed. The rod-shaped silicon single crystal 3 is grown by gently pulling up while rotating. On the other hand, the crucible 6 can be moved up and down in the direction of the crystal growth axis, and the crucible is raised so as to compensate for the liquid level drop of the melt that has been crystallized and decreased during the crystal growth, thereby increasing the height of the melt surface. Hold constant.

Further, an inert gas such as argon gas is introduced into the main chamber 1 from a gas inlet 10 provided in the upper portion of the pulling chamber 2, and the silicon single crystal 3 being pulled and the cooling cylinder 11 that is forcibly cooled. Or between the lower part of the heat shield member 14 for blocking radiation from the heater or the melt and the melt surface, and is discharged from the gas outlet 9. Here, the cooling cylinder 11 is forcibly cooled by the cooling medium introduced from the cooling medium introduction port 12.
Furthermore, using a radiation thermometer (not shown), the temperature of the raw material melt 4 in the crucible 6 can be measured from the radiation on the surface of the crystal melt through the glass window, and the temperature of the crystal melt can be measured.

Here, the crucible 6 that holds the raw material melt 4 is made of a material that has a higher melting point than silicon and does not contain oxygen atoms in its composition. The crucible here refers to a crucible that directly holds the raw material melt and contacts the raw material melt, and is not a support crucible used to supplement the strength of the conventional quartz crucible.
Further, when pulling up the single crystal, a magnetic field application device 15 applies a magnetic field for suppressing convection of the raw material melt 4.

  In this way, the crucible does not contain oxygen atoms in the composition, is stable at a temperature of about 1420 ° C., which is the melting point of silicon, and can form a crucible having a size capable of growing a silicon single crystal having a large diameter of, for example, 200 mm or more. By using this, it is possible to suppress the mixing of oxygen atoms into the raw material melt, which could never be avoided when using a quartz crucible. Accordingly, it is possible to prevent oxygen from being taken into the silicon single crystal, and it is possible to produce a silicon single crystal that substantially does not contain oxygen except for a small amount that is inevitably mixed. Therefore, it is possible to obtain a silicon single crystal wafer suitable for manufacturing a device for applications requiring high breakdown voltage such as a power device by the CZ method that can be easily increased in diameter, which greatly contributes to reduction of manufacturing cost. .

In addition, by applying a magnetic field, the single crystal cannot be pulled up because the convection of the raw material melt, which is a problem when using a large-diameter crucible that was not a problem in the conventional Patent Document 1 or the like, is not stable. And the production yield can be improved. Note that the silicon single crystal can be pulled up by forcibly generating convection of the raw material melt by greatly increasing the rotational speed of the crucible and the single crystal, but in this case, the single crystal is disturbed. In addition to the high probability of occurrence, the single crystal contains many crystal defects. However, according to the present invention, it is not necessary to significantly increase the number of rotations, and it is possible to increase the production efficiency of the silicon single crystal to be pulled up, reduce crystal defects, and achieve an improvement in quality. You can also.
Furthermore, because of the Czochralski method, for example, it is possible to easily handle the pulling of a silicon single crystal having a diameter of 200 mm or more, which is difficult with the FZ method. Further, the in-plane resistivity distribution when used as a wafer can be made uniform as compared with the wafer of the FZ method, and a silicon single crystal capable of producing a silicon single crystal wafer having a resistivity in-plane distribution within 10% is obtained. be able to.

  In addition, since no oxygen is contained in the crucible, no oxide is generated during the production of the silicon single crystal. Therefore, it is not necessary to consider the deterioration of the crucible and the adhesion of oxide in the furnace, so it is possible to produce a single crystal over a long period of time by multi-pooling that pulls up a large number of single crystal rods from the same crucible, reducing the running cost. In addition, the single crystal production yield can be further improved.

Here, the diameter of the silicon single crystal to be pulled can be set to 200 mm or more as described above.
As described above, the method for producing a silicon single crystal according to the present invention produces a silicon single crystal by the Czochralski method. Therefore, it is easy to increase the diameter compared to the FZ method. For example, even a silicon single crystal having a diameter of 200 mm or more, further 300 mm or more can be easily grown.

Further, as the crucible material to be used, a material made of any of carbon material, silicon carbide material, silicon nitride, boron nitride (PBN), tungsten, molybdenum, and niobium can be used.
Any material of carbon, silicon carbide, silicon nitride, boron nitride (PBN), tungsten, molybdenum, and niobium can easily form a crucible having a size capable of directly growing a crystal of 200 mm or more. Further, the composition does not contain oxygen, and is stable at about 1400 ° C. or higher, which is the melting point of silicon.
Accordingly, these materials are suitable because they can be prepared at low cost as materials having a melting point higher than that of silicon and not containing oxygen atoms in the composition. That is, by selecting these materials for the crucible material, it is possible to manufacture a silicon single crystal having an extremely low oxygen concentration more easily and inexpensively.

In addition, carbon may be mixed in the raw material melt from the carbon material and silicon carbide material listed here, carbon from the silicon nitride material, and nitrogen and boron from the PBN material.
However, boron is an effective element as a dopant, and there is no problem if resistance is controlled in consideration of the amount of elution.
Nitrogen is an element that is frequently doped in the FZ method. Also in the CZ method, it is an element that is intentionally doped in some varieties and has been confirmed to have an effect of reducing crystal defects. In the CZ crystal, it has been confirmed that nitrogen and oxygen act to increase BMD or form an NO donor. However, in the case of a silicon single crystal containing almost no oxygen as in the present invention, it may be considered that there is no effect of increasing BMD or forming NO donors.
Further, although carbon has been reported to form a donor in relation to oxygen, it is considered that this is not a problem with the silicon single crystal of the present invention containing almost no oxygen.

The applied magnetic field can be 500 Gauss or more and 6000 Gauss or less in intensity at the central portion on the solid-liquid interface of the silicon single crystal being pulled.
If the strength of the magnetic field at the central portion on the solid-liquid interface of the silicon single crystal being pulled is 500 Gauss or more, the effect of suppressing the convection of the crucible is large. For example, the larger the diameter of the crucible becomes 200 mm or more, the more problematic the crucible becomes. Convection can be suppressed. Moreover, if it is 6000 Gauss or less, the magnetic field generator which generate | occur | produces a high magnetic field will not become large sized, and the reduction of the cost concerning the problem of a leakage magnetic field and an apparatus can be achieved.
Furthermore, the elution of the crucible component can be suppressed by applying a magnetic field. Thereby, for example, even when a carbon crucible is used, a crystal having a low carbon concentration can be obtained.

  Further, during the pulling of the silicon single crystal, the in-plane distribution of the temperature gradient G in the vicinity of the growth interface and the pulling speed V of the silicon single crystal are controlled by adjusting the in-furnace structure. V / G can be controlled so that a defect-free region is generated.

As described above, the silicon single crystal manufactured by the FZ method not only contains almost no oxygen, but also can be made invisible to the extent of growing-in defects by doping nitrogen. These qualities may produce high breakdown voltage characteristics overall.
On the other hand, in the CZ method, as shown in JP-A-11-157996, JP-A-11-180800, and the like, a crystal growth technique free from grow-in defects can be achieved by using temperature gradient control in the furnace and an appropriate growth rate. Has been established.
Here, the grow-in defect will be described with reference to FIG.

  In general, when a silicon single crystal is grown, if the crystal growth rate V (crystal pulling rate) is relatively high, a grown-in defect such as COP that is caused by voids in which vacancy-type point defects are gathered is observed. It exists at high density throughout the crystal diameter direction. A region where defects due to these voids are present is called a V region.

  Further, when the crystal growth rate is lowered, an OSF (Oxidation Induced Stacking Fault) region is generated in a ring shape from the periphery of the crystal as the growth rate is lowered, and when the growth rate is further lowered, the OSF is reduced. The ring shrinks to the center of the wafer and disappears. On the other hand, when the growth rate is further reduced, defects such as LSEPD, which are considered to be caused by dislocation loops in which interstitial silicon is gathered, are present at a low density, and a region where these defects exist is called an I region.

  Further, there is a region outside the OSF ring between the V region and the I region, where there are no defects such as voids due to COP or defects such as LSEPD due to interstitial silicon, and this region is an N (neutral) region. be called.

The above-mentioned grow-in defect is a ratio between the pulling rate V (mm / min) of the single crystal and the crystal temperature gradient G (° C / mm) in the pulling axis direction between the melting point of silicon near the solid-liquid interface and 1420 ° C. The amount of introduction is considered to be determined by a parameter of V / G (mm ² / ° C. · min) (see, for example, VV Voronkov, Journal of Crystal Growth, 59 (1982), 625 to 643). .
That is, a single crystal having a desired defect region or a desired defect-free region can be manufactured by growing the single crystal while controlling V / G to be constant at a predetermined value.

Accordingly, V / G can be controlled in order to achieve a non-grow-in defect quality in order to approach the high breakdown voltage characteristics produced by the FZ crystal.
This makes it possible to grow a silicon single crystal having an extremely low oxygen concentration and no grown-in defects, and is therefore suitable for obtaining a defect-free high-quality silicon single crystal wafer.

  Here, the adjustment of the in-furnace structure can be performed by adjusting the positions and structures of the cooling cylinder 11, the cylinder 13, and the heat shield member 14, for example.

In addition, a slicing process for slicing a silicon single crystal manufactured by the above-described method for manufacturing a silicon single crystal of the present invention, a chamfering process for preventing cracking and chipping of a wafer obtained by the slicing process, and the wafer A lapping process for flattening, an etching process for removing chamfering and processing distortion remaining on the lapped wafer, a polishing process for mirroring the surface of the wafer, and an abrasive or a foreign substance adhered to the polished wafer by cleaning. A silicon single crystal having a very low oxygen concentration (1 × 10 ¹⁷ atoms / cm ³ (ASTM 79) or less) and a uniform in-plane resistivity distribution (within 10% error) A wafer can be obtained.

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
A silicon single crystal was grown using the single crystal growth apparatus based on the CZ method shown in FIG. 1, and a silicon single crystal wafer was manufactured from the obtained silicon single crystal.

Specifically, 160 kg of silicon raw material filled in a graphite crucible having a diameter of 24 inches (600 mm) without cracks or holes was heated and melted by a heater disposed so as to surround the graphite crucible. And after immersing a seed crystal in this raw material melt, the rod-shaped silicon single crystal was pulled up from the melted raw material by slowly raising the seed crystal.
A magnetic field having a strength of 4000 Gauss at the central portion on the solid-liquid interface of the silicon single crystal being pulled was applied. Further, the in-plane structure of the temperature gradient G in the vicinity of the growth interface was controlled by adjusting the in-furnace structure, and a single crystal was grown by controlling the V / G so that the growth rate V became a defect-free region (N region). .
Under the conditions described above, a silicon single crystal having a straight barrel length of 150 cm and a diameter of 8 inches (206 mm) was grown at a crucible rotation speed of 1 rpm and a crystal rotation speed of 12 rpm.

The crystal was cylindrically ground to a diameter of 200 mm, and a plurality of wafer-like samples were cut out every 30 cm.
Using these plural sample wafers, the oxygen concentration and resistivity in-plane distribution in the wafer were investigated.

First, the oxygen concentration in the wafer was measured using FT-IR. Specifically, it was evaluated by obtaining the oxygen absorption peak height from the difference in absorption spectrum between the sample wafer and the reference wafer. In this sample wafer, what was cut out from any position had almost the same absorption peak as that of the FZ crystal wafer used as a reference, and oxygen in the sample wafer was almost the same as that of the FZ crystal wafer. Therefore, there was no doubt that it was 1 × 10 ¹⁷ atoms / cm ³ or less.

Next, the resistivity in-plane distribution was evaluated. Six cut sample wafers were extracted, and the resistivity was measured in an in-plane 5 mm step. The result is shown in FIG.
As shown in FIG. 2, the percentage obtained by dividing the difference between the maximum value and the minimum value in the plane by the minimum value is 2-5%, which is less than 10%, which is difficult to achieve with the FZ method.
Furthermore, the defect distribution was investigated. The cut sample wafer was selectively etched and evaluated for FPD / LEP. As a result, it was confirmed that there was no defect.

(Example 2)
In Example 1, a silicon single crystal was pulled up under the same conditions except that boron nitride (PBN) was used for the crucible holding the raw material melt, and a silicon single crystal wafer was manufactured in the same manner, and the same evaluation was performed. It was.
As a result, the amount of oxygen in the sample wafer was the same level as that of the reference FZ crystal wafer, and was almost the same as that of the FZ crystal wafer as in Example 1. The resistivity in-plane distribution and crystal defect distribution were also almost the same.

(Example 3)
In Example 1, the silicon single crystal was pulled up under the same conditions except that silicon carbide (SiC) was used for the crucible holding the raw material melt, and a silicon single crystal wafer was produced in the same manner, and the same evaluation was performed. .
As a result, the amount of oxygen in the sample wafer was the same level as that of the reference FZ crystal wafer, and was almost equivalent to that of the FZ crystal wafer as in Examples 1 and 2. The resistivity in-plane distribution and crystal defect distribution were also almost the same.

(Comparative Example 1)
In order to achieve a low oxygen concentration by using a conventional silicon single crystal growing apparatus 16 ′ having a quartz crucible 17 as shown in FIG. 4, the rotational speed of the single crystal is 3 rpm and the rotational speed of the crucible is A silicon single crystal was pulled up under the same conditions as in Example 1 except that the rotation speed was extremely low at 0.02 rpm, and a silicon single crystal wafer was produced in the same manner, and the same evaluation was performed.

As a result, the oxygen concentration was 3-5 × 10 ¹⁷ atoms / cm ³ (ASTM 79).
However, there was a sample wafer with a resistivity in-plane distribution of about 15%, which was not so good.
With respect to crystal defects, a defect-free wafer could be obtained.
As described above, when a quartz crucible is used, a defect-free crystal is possible, but there are problems in terms of oxygen concentration and resistivity in-plane distribution.

(Comparative Example 2)
A silicon single crystal was grown under the same conditions as in Example 1 except that no magnetic field was applied.
However, it was difficult to pull up the single crystal because the convection of the raw material melt was not stable.
Therefore, the crucible rotation speed was increased to 8 rpm and the single crystal rotation speed was increased to 18 rpm to forcibly generate convection, so that the single crystal was finally pulled up.
However, after the straight body length of 100 cm, the single crystal was dislocated. Therefore, quality evaluation (wafer oxygen concentration, resistivity in-plane distribution, defect distribution) was performed only on the first half of the pulled single crystal.

As a result, the oxygen concentration was almost the same as that of the FZ crystal wafer as in Example 1. Also, the resistivity in-plane distribution was about 5%, well below 10%, and good results were obtained.
However, as a result of investigating crystal defects, no defect-free region was generated when FPD was detected or both FPD and LEP were detected in the plane.

This is presumably because the shape of the solid-liquid interface changed due to the absence of a magnetic field and the temperature gradient distribution changed significantly.
If the conditions are optimized, there is a possibility that defects can be obtained. However, even in the condition in which no defect is obtained in Example 1, it can be imagined that it is not easy in Comparative Example 2 because both FPD and LEP are detected in the sample wafer surface.
As described above, when no magnetic field is applied, there is no convection suppressing effect, so that it is difficult to pull up a large-diameter single crystal and it is difficult to obtain a defect-free crystal.

Empirically, the crucible size is preferably about three times the crystal size, and a diameter of about 24 inches (600 mm) is preferable for pulling a silicon single crystal having a diameter of 8 inches (200 mm).
Actually, in the pulling of a silicon single crystal having a diameter of 8 inches, a crucible of at least 18 inches (450 mm), usually 20 inches (500 mm) or more is used at most. However, when the crucible size increases, natural convection increases as in Comparative Example 2, and convection control is difficult unless forced convection is increased by rotation of the single crystal or the crucible. Further, when the crucible rotation or the like is increased in a large-diameter crucible, there are other problems such as that the surface of the raw material melt becomes unstable due to centrifugal force. Therefore, it has been found that it is necessary to pull up the silicon single crystal by the MCZ method having a convection suppressing effect.

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

1 ... Main chamber, 2 ... Lifting chamber,
3 ... Silicon single crystal, 4 ... Raw material melt, 5 ... Seed crystal, 6 ... Crucible,
DESCRIPTION OF SYMBOLS 7 ... Heating heater, 8 ... Heat insulation member, 9 ... Gas outflow port, 10 ... Gas introduction port, 11 ... Cooling cylinder, 12 ... Cooling medium introduction port, 13 ... Cylinder, 14 ... Heat insulation member, 15 ... Magnetic field application apparatus,
16, 16 '... Single crystal growing device,
17 ... Quartz crucible.

Claims (7)

A silicon single crystal wafer grown by the Czochralski method,
The silicon single crystal wafer is characterized in that the oxygen concentration is 1 × 10 ¹⁷ atoms / cm ³ (ASTM 79) or less and the resistivity in-plane distribution is within 10%. A method for producing a silicon single crystal,
When pulling up the silicon single crystal from the raw material melt by the Czochralski method,
At least using a crucible made of a material having a higher melting point than silicon and containing no oxygen atoms, and applying a magnetic field for suppressing convection of the raw material melt to the crucible holding the raw material melt A method for producing a silicon single crystal characterized by   3. The method for producing a silicon single crystal according to claim 2, wherein the material of the crucible is any one of carbon, silicon carbide, silicon nitride, boron nitride (PBN), tungsten, molybdenum, and niobium. .   The silicon single crystal production according to claim 2 or 3, wherein the applied magnetic field has a strength at a central portion on a solid-liquid interface of the silicon single crystal being pulled up to 500 Gauss or more and 6000 Gauss or less. Method.   During the pulling of the silicon single crystal, the in-plane distribution of the temperature gradient G in the vicinity of the growth interface and the pulling speed V of the silicon single crystal are controlled by adjusting the in-furnace structure. 5. The method for producing a silicon single crystal according to claim 2, wherein V / G is controlled so that a defect-free region is generated in the silicon substrate.   6. The method for producing a silicon single crystal according to claim 2, wherein a diameter of the silicon single crystal to be pulled is 200 mm or more.   A silicon single crystal wafer obtained by slicing a silicon single crystal manufactured by the method for manufacturing a silicon single crystal according to any one of claims 2 to 6.

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