JP2002087900A - Method of producing single crystal silicon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a single crystal silicon by which the high quality single crystal silicon, wherein the concentration of any one of silicon isotopes Si-28, Si-29 and Si-30 is higher than that in the natural silicon element, can be produced in large quantities. SOLUTION: The method of producing the single crystal silicon, wherein the concentration of the isotope Si-28 is higher than that of the isotope in the natural silicon element, comprises setting the concentration of the isotope Si-28 of the silicon element in a silicon melt 11 to be >=92.3% and setting the concentration of the isotope Si-28 of the silicon element in a seed crystal 13 to be >=92.3%. Further, when the single crystal is produced by a Czochralski method, quartz is used as a material for a crucible 12 for supporting the silicon melt 11 and the concentration of the isotope Si-28 of the silicon element in the quartz is also set to be >=92.3%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing single crystal silicon for semiconductor devices, and more particularly, to the concentration of any one of the isotopes Si-28, Si-29 and Si-30 of a silicon element. Is related to a method for producing single crystal silicon which is higher than a natural silicon element.

[0002]

2. Description of the Related Art Conventionally, individual semiconductor devices and semiconductor devices for semiconductor integrated circuits using a wafer made of single crystal silicon as a substrate or a substrate obtained by vapor-growing a silicon thin film on such a wafer as a substrate have been widely used. Has been
In recent years, rapid integration of silicon integrated circuit devices,
Heat generation of the element itself due to high speed operation and high power consumption is a problem. Since the heat generated by the integrated circuit causes a low speed of the element or causes a malfunction or destruction, a countermeasure against the heat is an important issue. The same applies to various power devices using a silicon substrate.

It has been confirmed that a part of the heat generated in a silicon integrated circuit or a silicon power device is radiated to the outside through a silicon substrate on which a circuit is formed.
By thinning the silicon substrate during the device fabrication stage,
The heat generated in the device can be efficiently released to the outside. In addition, a method has been devised to make the heat in the substrate easier to escape to the outside world by bringing the silicon substrate forming the semiconductor device into close contact with another material having a low temperature. Specifically, a method of physically contacting a silicon substrate with a heat sink, a method of externally cooling using an air cooling fan, a method of physically contacting a low-temperature device such as a Peltier element, and cooling with a refrigerant such as liquid nitrogen. There are methods.

As described above, conventionally, emphasis has been placed on cooling a semiconductor device from the outside. However, a method of improving the heat conductivity of the substrate itself by controlling the isotope composition of silicon to enhance the heat radiation efficiency has been described in the United States. It is disclosed in Japanese Patent Nos. 5144409 and 5442191. As described above, part of the heat generated in the silicon integrated circuit or the silicon power device is radiated to the outside through the silicon substrate on which the circuit is formed. Therefore, heat dissipation is promoted by increasing the thermal conductivity of the silicon substrate itself. It is possible.

The silicon element used for the substrate of such a semiconductor device is composed of three kinds of stable isotopes, Si-28, Si-29 and Si-30, and the composition ratio of these isotopes is natural. Of silicon, 92.23% of Si-28,
It is always constant at 4.67% for Si-29 and 3.10% for Si-30. The thermal conductivity of a single-crystal silicon substrate having a natural isotope composition is about 150 Wm ^-1 K ^-1 at room temperature, but the value of this thermal conductivity is such that three types of stable isotopes are mixed at the above constant composition ratio. It is restricted because of doing. Ruf et al.
Single-crystal silicon with a high isotope Si-28 concentration of 99.8588% was fabricated, and its thermal conductivity was 60% at 27 ° C compared to that of single-crystal silicon with natural isotope composition. ,
At 100 ° C it was shown to increase by more than 40% (Solid Sta
te Communication, Vol. 115, (2000), pp. 243-247). This means that the concentration of isotope Si-28 contained in single-crystal silicon is higher than the concentration of isotope Si-28 in natural silicon (9
(2.3% or more) suggests that the thermal conductivity of single crystal silicon can be increased. This is considered to be the same for the other isotopes Si-29 and Si-30.

Recently, a new quantum calculation method for controlling the nuclear spin distribution in a silicon crystal has been proposed. Among the above three isotopes constituting a silicon crystal, Si-29 having only one nuclear spin has been proposed. The technology for accurately adjusting the concentration of methane is important. Here, it is important to produce a silicon crystal containing the isotope Si-29 at a desired concentration (0 to 100%).

In producing a large silicon high power device such as a thyristor, a dopant (impurity intentionally added to adjust the electrical characteristics of silicon typified by phosphorus and boron) is uniformly contained in silicon. It is very important that they be distributed. If the distribution of the dopant is non-uniform, a strong electric field or a large current may be locally concentrated and the element may be destroyed. Therefore, a thermal neutron doping method using nuclear transmutation has been widely used as a measure against this problem. I have.
In this thermal neutron doping method, high-purity silicon crystals are placed in a nuclear reactor to irradiate thermal neutrons, but most of the irradiated thermal neutrons pass through the silicon crystal as they are and only a small part Only the neutrons are trapped by the Si-30 nucleus and the Si-30 is converted to Si-31. This Si-31 is nuclear-unstable and decays to P-31 (phosphorus), which causes the dopant phosphorus to appear randomly in the silicon crystal, resulting in a uniform distribution in the silicon crystal. I will be. Here, if Si-28 or Si-29 captures thermal neutrons, it is converted to stable silicon such as Si-29 or Si-30, so no doping effect can be obtained, but the parent silicon crystal is maintained. Will be done.

[0008] When such a thermal neutron doping method is used, phosphorus is uniformly distributed, so that excellent silicon can be obtained as a high power device material. However, damage to the crystal structure (defects of defects) due to prolonged neutron irradiation is obtained. Occurrence) can be a problem. As already mentioned, natural silicon elements include
Since it contains only 3.10% of Si-30, it is necessary to increase the concentration of Si-30 in the crystal significantly more than the natural 3.10% in order to increase the doping efficiency and shorten the irradiation time. . If the concentration of the isotope Si-30 is set to 100%, the doping efficiency is considered to be improved 33 times. In this case, however, the irradiation time is only 1/33, and the generation of crystal defects due to the irradiation can be suppressed. Thus, in order to improve the efficiency of thermal neutron doping, it is necessary to improve the efficiency of single crystal silicon.
It is desirable to increase the concentration of Si-30 even a little.

[0009] As a method for producing single crystal silicon, a Czochralski method (Cz method) and a floating zone method (Fz method) are generally used. In the Cz method, a polycrystalline silicon melt as a raw material of single crystal silicon is held in a crucible heated to a high temperature, and a seed crystal made of single crystal silicon suspended above the melt is brought into contact with the silicon melt. Thereafter, when this is slowly moved upward, silicon atoms in the silicon melt are regularly attached (solidified) to the seed crystal to form single crystal silicon. On the other hand, in the Fz method, a part of a solid silicon raw material in a rod shape is heated to a high temperature by a heater to be melted, and a seed crystal is slowly brought into contact with a silicon melt, which is the melting portion, and then the solid silicon raw material is separated. As a result, the silicon atoms in the silicon melt regularly adhere (solidify) with the seed crystal as a nucleus, and single crystal silicon is formed.

In the Cz method and the Fz method, in the first stage of the single crystal silicon production process, when the seed crystal comes into contact with the silicon melt, a part of the silicon atoms constituting the seed crystal is in the silicon melt. It is known to melt out. Natural isotope composition ratio (Si-28: 92.23%, Si-29: 4.6
(7%, Si-30: 3.10%), when producing single-crystal silicon, silicon having a natural composition ratio is used for the seed crystal and the silicon melt. Because the isotope composition ratios match, the partial melting of silicon atoms from the seed crystal into the silicon melt
The isotope composition ratio of the completed single crystal silicon does not change from the isotope composition ratio of the silicon melt.

In the Cz method, a crucible is used to hold a silicon melt. Quartz (SiO ₂ ) is usually selected as the crucible material. The silicon contained in the quartz crucible usually also has a natural isotope composition ratio, but the silicon melt in the crucible reacts with the inner surface of the crucible, and silicon atoms and oxygen atoms constituting the crucible are converted into silicon. Melts out in the melt. However, even in this case, the isotope composition ratio of silicon constituting the crucible matches the isotope composition ratio of the silicon melt, so that when producing single-crystal silicon having a natural isotope composition ratio, the crucible is used. Even if silicon atoms partially melt into the silicon melt, the isotope composition ratio of the completed single crystal silicon does not change from the isotope composition ratio of the silicon melt.

[0012]

However, the above 3)
If one of the silicon isotopes Si-28, Si-29, or Si-30 has a higher concentration than the natural silicon element, the isotope in the silicon melt Even if the concentration of the body is sufficiently higher than that of natural silicon, using natural silicon for the seed crystal and the crucible, the concentration of its isotope in single crystal silicon completed by crystal growth will be higher in the silicon melt. Concentration was lower than the concentration (Becker et al., IE
EE Transaction on Instrumentation and Measurement,
Vol.44 (1995) pp.525-525 and Ruf et al., Solid State Com
munications, Vol. 115 (2000) pp. 243-247). This is because when a seed crystal or a crucible having a low isotope concentration comes into contact with a silicon melt having a high isotope concentration, a seed crystal or a silicon atom in the crucible is mixed as an impurity into the silicon melt. This is probably because the concentration of the isotope in the silicon melt is reduced.

Further, when single crystal silicon having a certain silicon isotope concentration higher than that of a natural silicon is grown by using the Fz method which does not require a crucible, if no seed crystal is used, the crystal is grown. The composition ratio of the isotope in the rod-shaped raw material used for the growth is completely the same as the composition ratio of the isotope in the completed single crystal silicon (Takyu, Japanese Journal
of Applied Physics, Vol. 38 (1999) pp. L1493-L1495).
That is, unless a seed crystal and a crucible are used, the composition ratio of isotopes does not change during crystal growth, so that the concentration of any of the three silicon isotopes Si-28, Si-29, and Si-30 is reduced. This method can be used to produce single crystal silicon higher than the natural silicon element, but the crystal orientation cannot be controlled in any direction without a seed crystal, so that high quality single crystal silicon cannot be controlled. It is generally difficult to grow crystals. Although the production of single crystal silicon by such a method is possible at the laboratory level,
There is also a disadvantage that it is not suitable for mass production.

Thus, the silicon isotopes Si-28, Si-2
In the production of single-crystal silicon having a higher concentration of any of 9, Si-30 than natural silicon elements, it is difficult to efficiently obtain high-quality single-crystal silicon by a method without using a seed crystal. In particular, when single crystal silicon in which the isotope Si-28 is higher in concentration than natural silicon is used for a substrate of a semiconductor device or the like, the thermal conductivity is improved. ,
For this purpose, a method of growing single-crystal silicon using a conventional seed crystal is suitable, and a method of manufacturing single-crystal silicon based on such a conventional method is required.

The present invention has been made in view of such problems, and a single crystal in which the concentration of any of the silicon isotopes Si-28, Si-29, and Si-30 is higher than that of a natural silicon element. It is an object of the present invention to provide a method for producing single crystal silicon, which can produce silicon with good quality and mass production.

[0016]

Means for Solving the Problems The inventor of the present invention has made intensive studies to achieve such an object, and as a result, has completed the following method according to the present invention. That is, the first present invention relates to a method for producing single crystal silicon in which single crystal silicon is adhered and grown on the surface of a seed crystal contacted with a silicon melt,
Silicon isotopes in silicon melts and seed crystals.
In this method, the concentration of both Si-28 is 92.3% or more. In this method, since the concentration of the isotope Si-28 is not less than 92.3% not only in the silicon melt but also in the seed crystal, even if silicon atoms melt from the seed crystal during the growth of the single crystal silicon, the seed crystal is completed. Isotope Si-2 in single crystal silicon
The concentration of 8 is 92.3% or more, so that single crystal silicon having a higher concentration of the isotope Si-28 than the natural silicon element can be reliably obtained. Here, the concentration of the silicon element isotope Si-28 in the seed crystal is preferably substantially equal to the concentration of the silicon element isotope Si-28 in the silicon melt. In this way, the isotope in single crystal silicon
Since the concentration of Si-28 becomes almost the same as the concentration of isotope Si-28 in the silicon melt and the seed crystal, it is possible to precisely control the concentration of isotope Si-28 in the obtained single crystal silicon .

The Czochralski method and the floating zone method can be applied to this method. However, when the Czochralski method is applied, the material of the crucible holding the silicon melt is quartz. In addition, the concentration of the silicon element isotope Si-28 in the quartz is preferably 92.3% or more. More preferably, the concentration of the silicon element isotope Si-28 in the quartz is substantially equal to the concentration of the silicon element isotope Si-28 in the silicon melt.

According to a second aspect of the present invention, there is provided a method for producing single crystal silicon, wherein single crystal silicon is adhered and grown on a surface of a seed crystal contacted with the silicon melt. In this method, the concentration of Si-29 is set to 4.7% or more. In this method, since the concentration of the isotope Si-29 is not less than 4.7% not only in the silicon melt but also in the seed crystal, even if silicon atoms melt from the seed crystal during the growth of the single crystal silicon, the seed crystal is completed. The concentration of isotope Si-29 in single crystal silicon is 4.7%
As described above, single crystal silicon in which the concentration of the isotope Si-29 is higher than that of a natural silicon element can be surely obtained. Here, the isotope Si-2 of the silicon element in the seed crystal
The concentration of 9 isotope S of silicon element in silicon melt
Preferably, it is approximately equal to the concentration of i-29. In this way, the concentration of the isotope Si-29 in the single crystal silicon becomes almost equal to the concentration of the isotope Si-28 in the silicon melt and the seed crystal, and thus the obtained single crystal silicon isotope is obtained. It will be possible to control the Si-29 concentration accurately.

Further, the Czochralski method and the floating zone method can be applied to this method. In the case of applying the Czochralski method, the material of the crucible holding the silicon melt is quartz. Preferably, the concentration of the silicon isotope Si-29 in the quartz is not less than 4.7%. More preferably, the concentration of the silicon element isotope Si-29 in the quartz is substantially equal to the concentration of the silicon element isotope Si-29 in the silicon melt.

According to a third aspect of the present invention, there is provided a method for producing single crystal silicon, wherein single crystal silicon is adhered and grown on a surface of a seed crystal contacted with the silicon melt. In this method, the concentration of Si-30 is set to 3.2% or more. In this method, since the concentration of the isotope Si-30 is not less than 3.2% not only in the silicon melt but also in the seed crystal, even if silicon atoms melt from the seed crystal during the growth of single crystal silicon, the silicon crystal is completed. The concentration of isotope Si-30 in single crystal silicon is 3.2%
As described above, single crystal silicon in which the concentration of the isotope Si-30 is higher than that of a natural silicon element can be surely obtained. Here, the isotope Si-3 of the silicon element in the seed crystal
The concentration of 0 is the isotope S of the silicon element in the silicon melt
Preferably, it is approximately equal to the concentration of i-30. In this way, the concentration of the isotope Si-30 in the single crystal silicon becomes almost the same as the concentration of the isotope Si-28 in the silicon melt and the seed crystal. It will be possible to accurately control the Si-30 concentration.

The Czochralski method and the floating zone method can be applied to this method. In the case of applying the Czochralski method, the material of the crucible holding the silicon melt is quartz. Preferably, the concentration of the silicon element isotope Si-30 in the quartz is 3.2% or more. It is further preferable that the concentration of the silicon element isotope Si-30 in the quartz be substantially equal to the concentration of the silicon element isotope Si-30 in the silicon melt.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of an apparatus for manufacturing single crystal silicon using the method for manufacturing single crystal silicon according to one embodiment of the present invention. This apparatus is for producing single-crystal silicon by the conventionally known Czochralski method. A crucible 12 containing a silicon melt 11 is installed inside a pulling furnace 10 and is dropped from above the pulling furnace 10. After the seed crystal 13 is brought into contact with the silicon melt 11, it is gradually pulled upward while rotating to grow single crystal silicon.

A portion of the inner wall of the pulling furnace 10 surrounding the crucible 12 is covered with a heat insulating material 14, and a heater 15 for heating the crucible 12 to a high temperature is provided between the crucible 12 and the heat insulating material 14. I have. The crucible 12 is attached to the upper end of a rotating shaft 16 extending from the lower part of the lifting furnace 10, and the crucible 12 can be rotated horizontally by driving the rotating shaft 16 by a motor (not shown). The seed crystal 13 is attached to the lower end of a piano wire 17 extending vertically in the space above the pulling furnace 10, and the piano wire 17 is operated by a piano wire operating device (not shown) provided on the upper part of the pulling furnace 10. Then, the seed crystal 13 can be moved up and down or rotated around an axis.
The air inside the lifting furnace 10 is replaced with argon gas.

In order to produce single-crystal silicon using this apparatus, first, ultra-high-purity polycrystalline silicon, which is a raw material for single-crystal silicon, is roughly crushed and washed and put into a crucible 12. To produce a silicon melt 11. In the process of producing the silicon melt 11, a trace amount of impurities (doping agent) of a conductivity type is generally added. When the silicon melt 11 is formed, the crucible 12
Is rotated horizontally, the piano wire 17 is lowered, and the seed crystal 13
Is brought into contact with the silicon melt 11 (see FIG. 2A).

When the seed crystal 13 comes into contact with the silicon melt 11, the seed crystal 13 is gradually pulled upward while rotating in the direction opposite to the crucible 12. Thereby, silicon melt 1
The silicon atoms in 1 regularly adhere (solidify) to the surface of the seed crystal 13 to produce a target single crystal silicon 18 (see FIG. 2B). By adjusting the temperature of the silicon melt 11 at the time of pulling the seed crystal 13 and the pulling speed of the seed crystal 13, the diameter of the obtained single crystal silicon 18 can be set to desired values.

As described above, according to the present apparatus, single crystal silicon can be produced.
In order to produce single crystal silicon having a higher concentration of -28 than that of a natural silicon element, the concentration of the isotope Si-28 of the silicon element in the silicon melt 11 should be 92.3% or more, and the seed crystal 13 Is also 92.3% or more. In this way, even if silicon atoms melt out of seed crystal 13 during growth of single crystal silicon 18, completed single crystal silicon 18
In this case, the concentration of the isotope Si-28 becomes 92.3% or more, and the single crystal silicon 18 in which the concentration of the isotope Si-28 is higher than the natural silicon element can be surely obtained. Here, if the concentration of the silicon element isotope Si-28 in the seed crystal 13 is substantially equal to the concentration of the silicon element isotope Si-28 in the silicon melt 11, the isotope Si-28 in the single crystal silicon 18 is used. The concentration of Si is approximately equal to the concentration of the isotope Si-28 in the silicon melt 11 and the seed crystal 13, so that the concentration of the isotope Si-28 in the obtained single crystal silicon 18 can be accurately controlled. Becomes

In the case of the Czochralski method as in this apparatus, the material of the crucible 12 holding the silicon melt 11 is quartz, and the concentration of the silicon element isotope Si-28 in the quartz. Is preferably 92.3% or more. In this way, even if silicon atoms melt out of crucible 12 during the growth of single crystal silicon 18, isotope Si-2 in completed single crystal silicon 18
The concentration of 8 is 92.3% or more, so that the single crystal silicon 18 in which the concentration of the isotope Si-28 is higher than that of the natural silicon element can be surely obtained. Here, the isotope in the seed crystal 13
The concentration of Si-28 is almost equal to the concentration of the isotope Si-28 in the silicon melt 11, and the isotope Si-28 in the quartz
Is approximately equal to the concentration of the isotope Si-28 in the silicon melt 11, the single crystal silicon 1
8 is the concentration of the isotope Si-28
1. Since the concentration of the isotope Si-28 in the seed crystal 13 and the crucible 12 is almost the same, the concentration of the isotope Si-28 in the obtained single crystal silicon 18 can be accurately controlled.

The thus obtained single crystal silicon having a higher concentration of the isotope Si-28 (more than 92.3%) than the natural silicon element has a higher concentration than the conventional product when it is used as a semiconductor device wafer. Shows high thermal conductivity. Here, since the thermal conductivity of single crystal silicon is inversely proportional to the square of the mass number of the isotope, single crystal silicon having a high concentration of Si-28 is higher than single crystal silicon having a high concentration of Si-29 or Si-30. It is advantageous to have high thermal conductivity and to increase the concentration of the isotope Si-28 compared to natural silicon in order to enhance the heat dissipation effect of the semiconductor device. As described above, the technology that can easily and mass-produce single crystal silicon in which the concentration of the isotope Si-28 is higher than that of the natural silicon element is a technology for dissipating (radiating) heat generated in a semiconductor device, which is a conventional problem. Will contribute.

In order to produce single-crystal silicon having a higher concentration of the isotope Si-29 than that of the natural silicon element, the concentration of the silicon element isotope Si-29 in the silicon melt 11 is set to 4.7%. In addition to the above, the seed crystal 13
The concentration of the silicon element isotope Si-29 is also set to 4.7% or more. In this way, even if silicon atoms melt out of seed crystal 13 during growth of single crystal silicon 18, the concentration of isotope Si-29 in completed single crystal silicon 18 is
As a result, the concentration of the isotope Si-29 becomes 4.7% or more, so that the single crystal silicon 18 having a higher concentration than the natural silicon element can be reliably obtained. Here, if the concentration of the silicon element isotope Si-29 in the seed crystal 13 is substantially equal to the concentration of the silicon element isotope Si-29 in the silicon melt 11, the isotope Si-28 in the single crystal silicon 18 is used. Becomes approximately equal to the concentration of the isotope Si-29 in the silicon melt 11 and the seed crystal 13, so that the concentration of the isotope Si-29 in the obtained single crystal silicon 18 can be accurately controlled. Become.

If the apparatus is of the Czochralski method as in this apparatus, the material of the crucible 12 holding the silicon melt 11 is quartz, and the concentration of the silicon element isotope Si-29 in the quartz. Is also preferably set to 4.7% or more. By doing so, the single crystal silicon 1
Even if silicon atoms melt out of crucible 12 during growth of crystal 8, isotope Si-29 in completed single crystal silicon 18
Is not less than 4.7%, and the single crystal silicon 18 in which the concentration of the isotope Si-29 is higher than the natural silicon element can be surely obtained. Here, the isotope Si in the seed crystal 13
The concentration of -29 is approximately equal to the concentration of the isotope Si-29 in the silicon melt 11, and the concentration of the isotope Si-29 in the quartz is also approximately equal to the concentration of the isotope Si-29 in the silicon melt 11. If it is, single crystal silicon 18
The concentration of the isotope Si-29 in the silicon melt 11,
Since the concentration of the isotope Si-29 in the seed crystal 13 and the crucible 12 is almost the same, the concentration of the isotope Si-29 in the obtained single crystal silicon 18 can be accurately controlled.

The thus obtained single-crystal silicon having a higher isotope Si-29 concentration (more than 4.7%) than the natural silicon element has a higher isotope Si-29 concentration and nuclear spin distribution in the silicon crystal. This is particularly important in the technical field of studying the relationship with, and a technique that enables easy and large-scale production of single crystal silicon having such an isotope Si-29 concentration has great significance in such a technical field.

When it is desired to produce single-crystal silicon having a higher concentration of the isotope Si-30 than that of the natural silicon element, the concentration of the silicon element isotope Si-30 in the silicon melt 11 should be 3.2%. In addition to the above, the seed crystal 13
The concentration of the silicon element isotope Si-30 is also 3.2% or more. In this way, even if silicon atoms melt out of seed crystal 13 during the growth of single crystal silicon 18, the concentration of isotope Si-30 in completed single crystal silicon 18 is reduced.
It is 3.2% or more, so that the single crystal silicon 18 in which the concentration of the isotope Si-30 is higher than the natural silicon element can be surely obtained. Here, if the concentration of the silicon element isotope Si-30 in the seed crystal 13 is substantially equal to the concentration of the silicon element isotope Si-30 in the silicon melt 11, the isotope Si-30 in the single crystal silicon 18 is used. Becomes approximately equal to the concentration of the isotope Si-30 in the silicon melt 11 and the seed crystal 13, so that the concentration of the isotope Si-30 in the obtained single crystal silicon 18 can be accurately controlled. Become.

If the apparatus is of the Czochralski method as in this apparatus, the material of the crucible 12 holding the silicon melt 11 is quartz, and the concentration of the silicon element isotope Si-30 in the quartz. Is preferably not less than 3.2%. By doing so, the single crystal silicon 1
Even if silicon atoms melt out of crucible 12 during growth of crystal 8, isotope Si-30 in completed single crystal silicon 18
Is 3.2% or more, so that the single crystal silicon 18 in which the concentration of the isotope Si-30 is higher than the natural silicon element can be surely obtained. Here, the isotope Si in the seed crystal 13
The concentration of -30 is approximately equal to the concentration of the isotope Si-30 in the silicon melt 11, and the concentration of the isotope Si-30 in the quartz is also approximately equal to the concentration of the isotope Si-30 in the silicon melt 11. If it is, single crystal silicon 18
The concentration of the isotope Si-30 in the silicon melt 11,
Since the concentration of the isotope Si-30 in the seed crystal 13 and the crucible 12 substantially coincides with each other, the concentration of the isotope Si-30 in the obtained single crystal silicon 18 can be accurately controlled.

The thus obtained single crystal silicon having a higher isotope Si-30 concentration (3.2% or more) than the natural silicon element has a higher isotope Si-30 concentration than the natural silicon element. This is particularly important in the field of thermal neutron doping research, which aims to increase the efficiency of doping, and the technology that enables easy and large-scale production of single-crystal silicon with such isotope Si-30 concentration is very important in this field. It becomes important.

Here, when producing single crystal silicon in which the concentration of the isotope Si-28 is higher than that of the natural silicon element, the concentration of the isotope Si-28 in the seed crystal 13 is equal to the concentration of the silicon melt 1
It is preferable that the concentration of the isotope Si-28 in Example 1 is equal to or higher than the concentration of the isotope Si-28. The target single crystal silicon (single crystal silicon in which the concentration of the isotope Si-28 is higher than the natural silicon element) can be obtained with a much higher probability than the method. Further, the concentration of the isotope Si-28 in the crucible 12 is preferably equal to or higher than the concentration of the isotope Si-28 in the silicon melt 11, but at least the concentration of the isotope Si-28 in natural silicon is preferable. If it is higher, the target single crystal silicon can be obtained with a higher probability than the conventional method using a natural seed crystal (the same applies to Si-29 and Si-30).

FIG. 3 shows a method of manufacturing single crystal silicon according to another embodiment of the present invention, which is based on a floating zone method which has been conventionally performed.
In this method, a part of the bar-shaped solid silicon raw material 20 is heated to a high temperature by a heater 25 to be melted, and the seed crystal 23 is slowly brought into contact with the melting portion, that is, the silicon melt 21 (see FIG. 3A). Thereafter, the solid silicon raw material 20 is moved upward together with the heater 25 so that the seed crystal 23 is
When the silicon melt 21 is slowly pulled away from the silicon melt 21, the silicon melt 21 also moves upward, and in the process of movement, the silicon atoms in the silicon melt 21 regularly adhere (solidify) to the surface of the seed crystal 23, so that the target single crystal silicon 28 is formed. Formed (FIG. 3B)
reference). This step is performed in an argon atmosphere, as in the case of the Czochralski method described above.

Here, as in the case of the above-mentioned Czochralski method, when it is intended to produce single crystal silicon in which the concentration of the isotope Si-28 is higher than the natural silicon element,
Si-isotope Si-28 in silicon melt 21
(That is, the concentration of the silicon element isotope Si-28 in the solid silicon raw material 20) is 92.3% or more, and the silicon element isotope Si-28 in the seed crystal 23.
Concentration should be 92.3% or more. In this way, even if silicon atoms melt from seed crystal 23 during growth of single crystal silicon 28, the concentration of isotope Si-28 in completed single crystal silicon 28 becomes 92.3% or more, and isotope Si-28 -Crystalline silicon 18 with a higher concentration of silicon than natural silicon elements
Can be reliably obtained. Here, the concentration of the silicon isotope Si-28 in the seed crystal 23 is
1 is approximately equal to the concentration of the silicon element isotope Si-28,
Since the concentration of -28 becomes approximately equal to the concentration of isotope Si-28 in the silicon melt 21 and the seed crystal 23, the isotope Si-28 in the obtained single crystal silicon 28 is obtained.
The concentration can be accurately controlled.

When it is desired to produce single crystal silicon in which the concentration of the isotope Si-29 is higher than that of the natural silicon element, the concentration of the isotope Si-29 of the silicon element in the silicon melt 21 (ie, the solid The concentration of the silicon element isotope Si-29 in the silicon raw material 20) is set to 4.7% or more, and the silicon element isotope in the seed crystal 23 is set.
The concentration of Si-29 is also set to 4.7% or more. In this way, even if silicon atoms melt out of seed crystal 23 during the growth of single crystal silicon 28, the concentration of isotope Si-29 in completed single crystal silicon 28 becomes 4.7% or more, and isotope Si-29
Of silicon is higher than that of natural silicon element. Here, if the concentration of the silicon element isotope Si-29 in the seed crystal 23 is substantially equal to the concentration of the silicon element isotope Si-29 in the silicon melt 21, the isotope Si-29 in the single crystal silicon 28 Of the silicon melt 21 and the seed crystal 23
And the concentration of the isotope Si-29 in the single crystal silicon 28 is obtained.
9 It is possible to control the concentration accurately.

In order to produce single-crystal silicon having a higher concentration of the isotope Si-30 than that of the natural silicon element, the concentration of the silicon element isotope Si-30 in the silicon melt 21 (ie, the solid The concentration of the silicon element isotope Si-30 in the silicon raw material 20) is set to 3.2% or more, and the silicon element isotope in the seed crystal 23 is set.
The concentration of Si-30 is also set to 3.2% or more. In this way, even if silicon atoms melt out of seed crystal 23 during growth of single crystal silicon 28, the concentration of isotope Si-30 in completed single crystal silicon 28 becomes 3.2% or more, and isotope Si-30
Of silicon is higher than that of natural silicon element. Here, if the concentration of the silicon element isotope Si-30 in the seed crystal 23 is substantially equal to the concentration of the silicon element isotope Si-30 in the silicon melt 21, the isotope Si-30 in the single crystal silicon 28 is used. Of the silicon melt 21 and the seed crystal 23
Is approximately equal to the concentration of the isotope Si-30 in the single crystal silicon 28 obtained.
It is possible to accurately control 0 concentration.

Again, when producing single-crystal silicon where the concentration of the isotope Si-28 is higher than the natural silicon element,
The concentration of the isotope Si-28 in the seed crystal 23 is the same as that of the isotope in the silicon melt 21 (that is, the solid silicon raw material 20).
The concentration of Si-28 is preferably the same or higher, but at least the isotope Si-2 in natural silicon
If the concentration is higher than 8, the target single crystal silicon (the concentration of the isotope Si-28 is higher than the natural silicon element) with a much higher probability than the conventional method using natural seed crystals (Single-crystal silicon) is obtained (the same applies to Si-29 and Si-30).

When monocrystalline silicon is produced by the production method according to the present invention, it is preferable to use the Czochralski method or the floating zone method as described above. According to these methods, the prior art can be used as it is, and once the desired isotope Si-2
If a seed crystal having eight concentrations can be obtained, the desired single crystal silicon can be easily mass-produced thereafter.

Here, for the silicon melt 11 (21) made of polycrystalline silicon, isotopes Si-28, Si-29, Si
It is easy to adjust the concentration of -30 as desired. (Of these three isotopes, Si-28 is the most naturally abundant, and increasing the concentration of isotope Si-28 is difficult. Comparatively easy), the seed crystal 13 (2
Obtaining 3) is not always easy. Such a seed crystal can be obtained by a predetermined method without using a seed crystal (not the present method).
Can be obtained by cutting out the single crystal silicon obtained by the method described above, but there is also a method of obtaining by this method. For example, when it is desired to obtain a seed crystal in which the concentration of the isotope Si-28 is higher than the natural silicon element, first, single-crystal silicon is grown by the above method using natural silicon as a seed crystal, and the obtained single crystal is obtained. Silicon (this single crystal silicon is already the isotope Si-2
8 is higher than that of natural silicon), and the method may be repeated as a new seed crystal. As a result, the concentration of the isotope Si-28 in the seed crystal gradually increases, and finally the target isotope Si-28
A seed crystal having a -28 concentration is obtained (the same applies to Si-29 and Si-30).

[0043]

Hereinafter, a specific example of producing single crystal silicon having a higher concentration of isotope Si-28 than natural silicon using the method for producing single crystal silicon of the present invention will be described. It is not limited to. The embodiment described here uses the floating zone method shown in FIG. 3 to grow single-crystal silicon in the above-described steps. Both the rod-shaped solid silicon raw material 20 and the seed crystal 23 used for crystal growth have a higher concentration of isotope Si-28 than natural silicon, and the isotope composition is determined by secondary ion mass spectrometry before crystal growth. As a result of measurement using a device (SIMS), the isotope compositions of the seed crystal 23 and the solid silicon raw material 20 completely match, and 99.924% of Si-28 and 0.2% of Si-29 were used.
073% and Si-30 were 0.003%.

After the crystal growth, the isotopic composition of the single crystal silicon 28 was measured again by SIMS. As measurement points, five points at equal intervals in the length direction of the completed single crystal silicon 28 were selected. The shape of the single crystal silicon 28 was a column having a length of 50 mm and a diameter of about 5 mm. As a result, at all the measurement points (5 points), Si-28 was 99.924%, Si-29 was 0.073%, S
The value of i-30 was completely equal to 0.003%, and was completely consistent with the measurement results of the isotope compositions of the solid silicon raw material 20 and the seed crystal 23 before the crystal growth. Thus, if the concentration of the silicon isotope Si-28 in the seed crystal 23 as well as the silicon raw material 20 (that is, the silicon melt 21) is higher than the concentration of the isotope Si-28 in natural silicon, It has been proved that single crystal silicon having a higher body Si-28 concentration than natural silicon elements can be obtained. Also,
The composition ratio of the isotopes in the seed crystal 23
If the composition ratio of the isotopes in (ie, the silicon melt 21) is the same, the composition ratio of the isotopes in the obtained single-crystal silicon is the silicon raw material 20 (and the seed crystal 23).
It was proved that the composition ratio became the same as that of the isotope in Example 1.

[0045]

As described above, in the first method for producing single-crystal silicon according to the present invention, single-crystal silicon is produced by adhering and growing single-crystal silicon on the surface of a seed crystal brought into contact with a silicon melt. In the method, the concentration of the isotope Si-28 of the silicon element in the silicon melt and the seed crystal is set to 92.3% or more. According to this method, the concentration of the isotope Si-28 is 92.3% not only in the silicon melt but also in the seed crystal.
Therefore, even if silicon atoms melt from the seed crystal during the growth of single crystal silicon, the concentration of the isotope Si-28 in the completed single crystal silicon is 92.3% or more, and the concentration of the isotope Si-28 Can reliably obtain single crystal silicon higher than natural silicon elements.

Further, in the second method for producing single crystal silicon according to the present invention, the method for producing single crystal silicon in which single crystal silicon is adhered and grown on the surface of a seed crystal brought into contact with the silicon melt is provided. And the concentration of the silicon element isotope Si-29 in the seed crystal is set to 4.7% or more. In this method, since the concentration of the isotope Si-29 is not less than 4.7% not only in the silicon melt but also in the seed crystal, even if silicon atoms melt from the seed crystal during the growth of single crystal silicon, the silicon crystal is completed. The concentration of the isotope Si-29 in single crystal silicon is 4.7% or more, so that single crystal silicon in which the concentration of the isotope Si-29 is higher than that of a natural silicon element can be reliably obtained.

Further, in the third method for producing single crystal silicon according to the present invention, the method for producing single crystal silicon in which single crystal silicon is adhered and grown on the surface of a seed crystal contacted with the silicon melt is provided. In addition, the concentration of the silicon element isotope Si-30 in the seed crystal is set to 3.2% or more. In this method, since the concentration of the isotope Si-30 is not less than 3.2% not only in the silicon melt but also in the seed crystal, even if silicon atoms melt from the seed crystal during the growth of single crystal silicon, the silicon crystal is completed. The concentration of the isotope Si-30 in single crystal silicon is 3.2% or more, so that single crystal silicon in which the concentration of the isotope Si-30 is higher than that of a natural silicon element can be reliably obtained.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a single-crystal silicon manufacturing apparatus using a Czochralski method, corresponding to one embodiment of a single-crystal silicon manufacturing method according to the present invention.

FIG. 2 is a diagram showing a procedure of the Czochralski method,
(A) shows a state in which the seed crystal is about to be brought into contact with the silicon melt, and (B) shows a state in which the seed crystal brought into contact with the silicon melt is pulled to grow single crystal silicon.

FIG. 3 is a view showing a procedure of a floating zone method corresponding to another embodiment of the method for producing single crystal silicon according to the present invention, wherein (A) shows a state where a seed crystal is about to be brought into contact with a silicon melt. (B) shows a state in which, after the seed crystal is brought into contact with the silicon melt, the solid silicon raw material is pulled up to grow single crystal silicon.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Pulling furnace 11 Silicon melt 12 Crucible 13 Seed crystal 14 Insulation material 15 Heater 16 Rotation axis 17 Piano wire 18 Single crystal silicon

Claims (13)

[Claims] 1. A method for producing single crystal silicon, in which single crystal silicon is adhered and grown on the surface of a seed crystal that has been brought into contact with a silicon melt, comprising the steps of: isolating Si-28 of a silicon element in the silicon melt and the seed crystal; A method for producing single crystal silicon, wherein the concentrations are both 92.3% or more. 2. The single crystal according to claim 1, wherein the concentration of the silicon element isotope Si-28 in the seed crystal is substantially equal to the concentration of the silicon element isotope Si-28 in the silicon melt. Silicon manufacturing method. 3. The method of growing a single crystal silicon according to the Czochralski method, wherein a material of a crucible holding the silicon melt is quartz, and a concentration of a silicon element isotope Si-28 in the quartz is reduced. 3. The method for producing single crystal silicon according to claim 1, wherein the content is 92.3% or more. 4. An isotope of a silicon element in the quartz.
4. The method according to claim 3, wherein the concentration of Si-28 is substantially equal to the concentration of the isotope Si-28 of the silicon element in the silicon melt. 5. A method for producing single-crystal silicon, in which single-crystal silicon is adhered and grown on the surface of a seed crystal that has been brought into contact with a silicon melt, the method comprising the steps of: A method for producing single-crystal silicon, wherein both the concentrations are not less than 4.7%. 6. The single crystal according to claim 5, wherein the concentration of the silicon element isotope Si-29 in the seed crystal is substantially equal to the concentration of the silicon element isotope Si-29 in the silicon melt. Silicon manufacturing method. 7. The method of growing a single crystal silicon according to the Czochralski method, wherein the material of the crucible holding the silicon melt is quartz, and the concentration of the silicon element isotope Si-29 in the quartz is reduced. 7. The method for producing single crystal silicon according to claim 5, wherein the content is not less than 4.7%. 8. An isotope of a silicon element in the quartz
The method for producing single crystal silicon according to claim 7, wherein the concentration of Si-29 is substantially equal to the concentration of the isotope Si-29 of the silicon element in the silicon melt. 9. A method for producing single-crystal silicon, in which single-crystal silicon is adhered and grown on the surface of a seed crystal that has been brought into contact with a silicon melt, the method comprising the steps of: A method for producing single crystal silicon, wherein the concentrations are both 3.2% or more. 10. The single crystal according to claim 9, wherein the concentration of the silicon element isotope Si-30 in the seed crystal is substantially equal to the concentration of the silicon element isotope Si-30 in the silicon melt. Silicon manufacturing method. 11. The method of growing the single crystal silicon according to the Czochralski method, wherein the material of the crucible holding the silicon melt is quartz, and the concentration of the silicon element isotope Si-30 in the quartz is The method for producing single crystal silicon according to claim 9 or 10, wherein the content is 3.2% or more. 12. The single crystal silicon according to claim 11, wherein the concentration of the silicon element isotope Si-30 in the quartz is substantially equal to the concentration of the silicon element isotope Si-30 in the silicon melt. Manufacturing method. 13. The method according to claim 1, wherein the single crystal silicon is grown by a floating zone method.
The method for producing single-crystal silicon according to any one of 2, 5, 6, 9, and 10.