JP6939456B2 - Silicon single crystal growing device and silicon single crystal manufacturing method - Google Patents

Description

The present invention relates to an apparatus for growing and manufacturing a semiconductor silicon single crystal (FZ silicon single crystal) by the FZ method (floating zone method or floating zone melting method).

The FZ method is used, for example, as one of the methods for producing a semiconductor single crystal such as a silicon single crystal, which is currently most often used as a semiconductor element. FIG. 6 shows an example of the manufacturing process of the FZ silicon single crystal. A semiconductor rod (raw material rod) as a raw material is arranged above the high-frequency coil to which a high-frequency induced current is applied, and a single crystal seed crystal is arranged below. The lower end of the raw material rod is melted and fused to the seed crystal ((a) seeding step), and further drawing (necking) is performed to remove dislocations generated in the crystal during this seeding ((b)). Necking step), and then the crystallized side semiconductor rod (semiconductor single crystal rod) is grown while being expanded to a desired diameter ((c) cone portion forming step). Further, the crystallizing side semiconductor rod is grown while being controlled to a desired diameter ((d) straight body forming step), the supply of raw materials is stopped, and the diameter of the crystallizing side semiconductor rod is reduced to reduce the crystallizing side. The semiconductor rod is separated from the raw material semiconductor rod ((e) separation step). A semiconductor single crystal (FZ silicon single crystal) can be produced through the above steps.

However, during the production of a single crystal by the FZ method, the melting of the raw material may become non-uniform and a protrusion-like undissolved residue (called Hana) may occur on the molten surface. In particular, when polycrystalline silicon is used for the raw material rod, the non-uniform crystal structure further promotes the difference between the portion that is easily melted and the portion that is difficult to melt, so that the frequency of occurrence of Hana increases. If such a shaving is generated and does not melt and remains for a long time, the single crystal production cannot be continued due to a defect such as contact with the high frequency coil and discharge, and the production process must be completed.

In order to prevent this, for example, as shown in Non-Patent Document 1, a metal ring (short ring) having high conductivity such as copper is arranged above the high frequency coil so as to surround the raw material rod to produce a single crystal. (See FIG. 4). In this case, the density of the magnetic flux passing through the short ring 4 changes, and a reverse induced current that cancels the change in the magnetic flux density flows through the short ring. The magnetic flux generated by this reverse induced current increases the magnetic flux density between the short ring on the lower side of the raw material rod and the high frequency coil, and conversely decreases the magnetic flux density on the upper side of the short ring. As a result, the temperature gradient in the axial direction of the raw material rod is increased, and by rapidly heating and melting in the vicinity of the raw material melting surface, the heating non-uniformity of the molten portion can be reduced and the generation of honey can be suppressed.

By using the short ring in this way, the magnetic field strength can be increased in the vicinity of the raw material melting portion to achieve uniform melting of the raw material, but at the same time, the FZ input power is increased as a whole. Further, since the high-frequency coil has a non-axisymmetric shape, heating is not always uniform in each direction in the crystal cross-sectional direction, and an increase in the FZ input power promotes non-uniform heating of the high-frequency coil. As a result, the degree of heating fluctuation during FZ crystal growth increases, causing dislocation due to increased thermal stress, or polycrystalline growth due to rapid dissolution and rapid solidification of the single crystallized portion, which inhibits single crystal growth. It becomes a factor to do. As described above, the conventional technique is not preferable because it hinders the acquisition of a sufficient single crystal and leads to a decrease in productivity and yield.

WOLFGANG KELLER, ALFRED MUHLBAUER, "Floating-Zone Silicon" p. 15-17, MARCEL DEKKER, INC. Issue

The present invention has been made in view of such circumstances, and when a metal ring (short ring) is used in the production of a semiconductor single crystal by the FZ method, stable melting of the raw material rod becomes possible. It is an object of the present invention to provide such a silicon single crystal growing apparatus and a silicon single crystal manufacturing method.

In order to achieve the above problems, in the present invention, the chamber, the upper shaft for attaching the raw material rod, the lower shaft for attaching the seed crystal, the high frequency coil for melting the raw material rod, and the above the high frequency coil. A silicon single crystal growing apparatus by the FZ method including a metal ring arranged so as to surround a raw material rod, in which a closed circuit in which the main body of the metal ring is a main circuit is formed and the metal ring is formed. Provided is a silicon single crystal growing apparatus in which a closed circuit serving as a sub circuit is further provided.

By using the metal ring provided with the sub-circuit in this way, the heating of the raw material can be further concentrated in the vicinity of the molten portion, so that the generation of the raw material can be further suppressed. In addition, the stable melting of the raw material rod is performed more efficiently, so that the FZ input power is reduced, and dislocations occur due to an increase in thermal stress, or polycrystalline growth occurs due to rapid melting and rapid solidification of the single crystallized portion. Can be suppressed.

In this case, it is preferable that the metal ring is provided with two or more subcircuits.

A silicon single crystal growing apparatus provided with such a metal ring enables more stable melting of the raw material rod.

Further, it is preferable that the metal ring is provided with a sub circuit above the plane formed by the main circuit of the metal ring.

In the case of a silicon single crystal growing apparatus provided with a metal ring provided with such a three-dimensional sub-circuit, stable melting of the raw material rod is performed more reliably, dislocation due to an increase in thermal stress, or a single crystal. It is possible to further suppress the occurrence of polycrystalline growth due to rapid dissolution and rapid solidification of the converted portion.

Further, the present invention is a method for producing a silicon single crystal by the FZ method, in which a raw material rod is attached to an upper shaft and a seed crystal is attached to a lower shaft in a chamber, and then the raw material rod is surrounded above a high-frequency coil. When the metal ring is arranged as described above and the raw material rod is melted by the high frequency coil to produce a silicon single crystal, a closed circuit in which the main body of the metal ring is the main circuit is formed as the metal ring. Further, the present invention provides a method for producing a silicon single crystal using the metal ring further provided with a closed circuit serving as a sub circuit.

By using the metal ring provided with the sub-circuit in this way, the heating of the raw material can be further concentrated in the vicinity of the molten portion, so that the generation of the raw material can be further suppressed. In addition, the stable melting of the raw material rod is performed more efficiently, so that the FZ input power is reduced, and dislocations occur due to an increase in thermal stress, or polycrystalline growth occurs due to rapid melting and rapid solidification of the single crystallized portion. Can be suppressed.

In this case, it is preferable that the metal ring is provided with two or more subcircuits.

With such a metal ring, more stable melting of the raw material rod becomes possible.

Further, it is preferable that the metal ring is provided with a sub circuit above the plane formed by the main circuit of the metal ring.

With such a metal ring provided with a three-dimensional sub-circuit, stable melting of the raw material rod is performed more reliably, dislocations occur due to an increase in thermal stress, or the single crystallized portion is rapidly melted or rapidly melted. It is possible to further suppress the occurrence of polycrystalline growth due to solidification.

As described above, in the case of the silicon single crystal growing apparatus and the silicon single crystal manufacturing method of the present invention, in the manufacturing of the semiconductor single crystal by the FZ method using a metal ring, the heating of the raw material can be further concentrated in the vicinity of the melting portion. Therefore, it is possible to further suppress the generation of shavings as a raw material, and the FZ input power is reduced. This is a direction away from the single crystal growth-inhibited state, which leads to an improvement in the crystal acquisition rate, that is, an improvement in productivity and yield, leading to a stable supply of products. Further, even when a highly difficult production condition is applied in order to acquire a higher quality crystal, it is possible to compensate for the decrease in the crystal acquisition rate. Therefore, it is possible to provide a silicon single crystal growing apparatus and a silicon single crystal production method capable of more efficiently stable melting of a raw material rod when a metal ring is used in the production of a semiconductor single crystal by the FZ method. ..

This is an example of a metal ring used in the silicon single crystal growing apparatus of the present invention. This is an example of a metal ring used in a conventional silicon single crystal growing apparatus. This is an example of a silicon single crystal growing apparatus by the FZ method. It is a figure for demonstrating the action effect of a metal ring in the prior art. It is a figure for demonstrating the action and effect of a metal ring in this invention. This is an example of a silicon single crystal manufacturing method by the FZ method.

As described above, in the production of a semiconductor single crystal by the FZ method, a silicon single crystal growing apparatus and a silicon single crystal production method that enable stable melting of a raw material rod more efficiently when a metal ring is used. Development was required.

Conventionally, as a measure to prevent the generation of shavings during single crystal production by the FZ method, crystals can be obtained without problems by using a metal ring, and there is no problem in stable production. However, in recent years, the market demand for larger diameter and higher quality single crystals has been met, and along with this, the single crystal production conditions have changed to more difficult ones, and the FZ input power has also increased. For this reason, the degree of non-uniform heating of the high-frequency coil increases, and from a microscopic point of view, the difference between the part where the raw material rod melts and the part where it does not melt becomes large. From this point of view, the increase in thermal stress applied to the crystal tended to inhibit the growth of the single crystal.

After studying to deal with such a problem, we came up with the idea of using a metal ring having a shape in which a sub circuit is further provided in addition to the closed circuit (main circuit) of the main body. The crystal growth device and the silicon single crystal production method were completed.

That is, the present invention surrounds the raw material rod above the chamber, the upper shaft for attaching the raw material rod, the lower shaft for attaching the seed crystal, the high frequency coil for melting the raw material rod, and the high frequency coil. A silicon single crystal growing apparatus by the FZ method provided with a metal ring arranged in, which forms a closed circuit in which the main body of the metal ring serves as a main circuit, and a closed circuit in which the metal ring serves as a sub circuit. Is a silicon single crystal growing apparatus further provided with.

Hereinafter, the present invention will be specifically described, but the present invention is not limited thereto.

FIG. 1 shows an example of a metal ring (short ring) used in the silicon single crystal growing apparatus of the present invention. Such a metal ring 1 is composed of a main body 2 and a sub circuit 3. The main body 2 forms a closed circuit as a main circuit, and the sub circuit 3 forms a closed circuit as a sub circuit together with a part of the main body. Further, FIG. 2 shows a conventionally used metal ring as disclosed in Non-Patent Document 1 described above. The structure of the metal ring in FIG. 2 is only the main body 2, and the main body 2 forms a closed circuit as a main circuit, but a sub circuit is not formed. As described above, it is a feature of the present invention that a closed circuit in which the metal ring serves as a sub circuit is further provided.

Further, it is preferable that the metal ring is provided with two or more subcircuits. Further, it is more preferable that the metal ring is provided with a sub circuit above the plane formed by the main circuit of the metal ring. Further, the height of the auxiliary circuit is preferably about half the diameter of the raw material rod.

The metal ring used in the silicon single crystal growing apparatus of the present invention is not particularly limited as long as it is made of a metal having high conductivity, but it is preferably made of copper. Further, it is preferable that the inside of the metal ring is hollow (that is, pipe-shaped) so that cooling water can flow. When the metal ring is in the shape of a pipe, it is possible to prevent the metal ring at a high temperature from being melted and damaged when the silicon single crystal growing apparatus of the present invention is used for producing a silicon single crystal.

The basic apparatus configuration used in the present invention is the same as that of the conventional apparatus except that a metal ring is used. For example, the metal ring 1 as shown in FIG. 1 is installed in the silicon single crystal growing apparatus 21 of FIG. The device can be used.

Hereinafter, the silicon single crystal growing apparatus of the present invention will be described. In the silicon single crystal growing apparatus 21 of FIG. 3, an upper shaft 12 and a lower shaft 13 are provided in the chamber 11. A semiconductor rod having a predetermined diameter is attached to the upper shaft 12 as a raw material rod 14 (raw material semiconductor rod), and a seed crystal 15 is attached to the lower shaft 13. Further, a high-frequency coil 16 for melting the raw material rod 14 is provided, and the crystallized semiconductor rod 19 can be grown while moving the melting zone 18 relatively upward with respect to the raw material rod 14. Further, during the growth, the dopant gas can be supplied from the dopant gas dope nozzle 20 (dopant gas supply means). In FIG. 3, the metal ring 1 as shown in FIG. 1, which is a feature of the present invention, is arranged above the high-frequency coil 16 so as to surround the raw material rod 14.

Hereinafter, the action and effect of the metal ring will be described in more detail with reference to FIGS. 4 and 5. Even in the prior art as in Non-Patent Document 1, the metal ring 4 is arranged above the high-frequency coil 16 so as to surround the raw material rod to produce a single crystal. When the magnetic flux is applied by the high-frequency coil 16, the density of the magnetic flux 5 passing through the metal ring changes, and a reverse induced current 6 that cancels the change in the magnetic flux density flows through the metal ring. The magnetic flux 7 generated by the reverse induced current 6 increases the magnetic flux density between the metal ring on the lower side of the raw material rod and the high-frequency coil, and conversely decreases the magnetic flux density on the upper side of the metal ring. As a result, the temperature gradient in the axial direction of the raw material rod is increased, and by rapidly heating and melting in the vicinity of the raw material melting surface, the heating non-uniformity of the molten portion can be reduced and the generation of honey can be suppressed.

On the other hand, in contrast to the prior art, in the present invention, as shown in FIG. 5, in order to further enhance the effect of the metal ring, for example, in addition to the closed circuit (main circuit) of the main body as shown in FIG. Separately, a metal ring 1 having a shape in which a sub circuit is further provided is used. With such a shape, in addition to the effect of the main circuit of the metal ring body, the effect of the sub circuit (additional closed circuit) can be expected. That is, as shown in FIG. 5, a reverse induced current 9 in a direction that captures a change in the density of the magnetic flux 8 passing through the sub circuit and cancels the change flows in the sub circuit. Further, the current flowing through the common portion with the main circuit of the sub circuit is in the same direction as the main circuit, and the magnetic flux 10 on the main body side is strengthened. As a total sum including the magnetic flux of the high-frequency coil, the change in magnetic flux density between the metal ring and the high-frequency coil is larger than in the conventional case, and the change in magnetic flux density is larger in the range where the sub circuit above the metal ring body is provided. It becomes smaller. That is, by using a metal ring having this shape, the temperature gradient at the time of heating the raw material is further increased as compared with the conventional case, so that the effect of preventing the generation of honey is also increased and the raw material can be melted efficiently, so that FZ is applied. The electric power is reduced and crystals can be obtained stably.

At this time, since the change in the magnetic flux density increases as the amount of magnetic flux passing through the sub-circuit increases, it is better to take a large sub-circuit and capture a larger amount of magnetic flux. However, if a single closed circuit is provided in this way, the shape becomes unstable and tends to cause problems. Therefore, it is practically effective to provide a plurality of closed circuits and appropriately arrange them according to the crystal manufacturing state to be applied. In the aspects of FIGS. 1 and 5, two subcircuits are formed on the left and right sides of the drawing. Of course, three or four or more may be formed.

Further, regarding the sub-circuit, the magnetic flux that cannot be captured in the same plane is generated by providing the sub-circuit above the main body, for example, as shown in FIG. 1, not in the plane formed by the metal ring main body. It is more effective because it can pass through a closed circuit and can utilize a three-dimensional magnetic flux.

Further, the present invention is a method for producing a silicon single crystal by the FZ method, in which a raw material rod is attached to an upper shaft and a seed crystal is attached to a lower shaft in a chamber, and then the raw material rod is surrounded above a high frequency coil. When the metal ring is arranged as described above and the raw material rod is melted by the high frequency coil to produce a silicon single crystal, a closed circuit in which the main body of the metal ring is the main circuit is formed as the metal ring. Moreover, it is a silicon single crystal manufacturing method using the metal ring further provided with a closed circuit serving as a sub circuit.

In this case, it is preferable that the metal ring is provided with two or more subcircuits. Further, it is more preferable that the metal ring is provided with a sub circuit above the plane formed by the main circuit of the metal ring.

Next, an example of the silicon single crystal production method of the present invention will be described in more detail with reference to FIG. First, as a raw material rod 14, a silicon polycrystalline rod having a predetermined diameter is attached to the upper shaft 12, and a seed crystal 15 is attached to the lower shaft 13. Next, a metal ring 1 (for example, the metal ring of FIG. 1) further provided with an auxiliary circuit is arranged above the high-frequency coil 16 so as to surround the raw material rod 14, and the raw material rod 14 is melted by the high-frequency coil 16. After that, it is fused to the seed crystal 15. The crystallizing side semiconductor rod 19 to be grown from the seed crystal is dislocated by the drawing 17, and both axes are rotated and relatively lowered, and the melting zone 18 is moved relatively upward with respect to the raw material rod 14. The crystallizing side semiconductor rod 19 (silicon single crystal) is grown.

After the drawing 17 is formed, the crystallization side semiconductor rod 19 to be grown from the seed crystal is grown while expanding the diameter to a desired diameter to form a cone portion, and between the raw material rod 14 and the crystallization side semiconductor rod 19. The melting zone 18 is formed, and the crystallizing side semiconductor rod 19 is grown while being controlled to a desired diameter to form a straight body portion. Then, the melting zone 18 is moved to the upper end of the raw material rod 14, the growth of the crystallizing side semiconductor rod 19 (silicon single crystal) is completed, the diameter of the crystallizing side semiconductor rod 19 is reduced, and the crystallizing side semiconductor rod 19 is reduced in diameter. 19 is separated from the raw material rod 14 to produce a semiconductor silicon single crystal.

In the method for producing a silicon single crystal of the present invention, a metal ring 1 further provided with an auxiliary circuit is arranged above the high-frequency coil 16 so as to surround the raw material rod 14, and the raw material rod 14 is melted by the high-frequency coil 16. There is a feature in. By using such a metal ring 1, the heating non-uniformity of the molten portion is reduced by rapidly heating and melting in the vicinity of the raw material melting surface as compared with the case where the conventional metal ring 4 is used, and the generation of honey is generated. It can be further suppressed.

Hereinafter, the present invention will be described in more detail with reference to examples of the present invention, but the present invention is not limited thereto.

[Example]
When manufacturing a semiconductor silicon single crystal by the FZ method having a diameter of 205 mm using a polycrystalline raw material rod having a diameter of 150 mm, a crystal is used by using an apparatus in which a metal ring having a shape shown in FIG. 1 is attached to the apparatus of FIG. The acquisition trial was carried out 15 times. There was no Hana outbreak at this time. Of the 15 trials, 14 times, a single crystal could be obtained without dislocation until the end. One of the 15 trials was dislocated in the middle of the straight body, but more than 80% of the part could be obtained as a single crystal.

[Comparison example]
A semiconductor silicon single crystal was produced by the FZ method under the same conditions as in the examples except that the metal ring of FIG. 2 was used instead of the metal ring of FIG. 1, and crystal acquisition trials were carried out 15 times. At this time, out of 15 crystal acquisition trials, the generation of hana was remarkable, and one of them was a discharge on the high-frequency coil by the hana, and the single crystal production was completed. Once again, Hana such as electric discharge was not found to be the direct cause, but it was dislocated in the straight body.

As a result, 3 times out of 15 trials were dislocated in the middle of the straight body, and 1 time was completed by electric discharge (including the above-mentioned trouble). In the remaining 11 times, a single crystal could be obtained without dislocation until the end.

As described above, the silicon single crystal growing apparatus and the silicon single crystal manufacturing method of the present invention enable more efficient stable melting of raw material rods when a metal ring is used in the manufacturing of semiconductor crystals by the FZ method. It turned out to be.

The present invention is not limited to the above embodiment. The above-described embodiment is an example, and any technical scope of the present invention having substantially the same configuration as the technical idea described in the claims of the present invention and having the same effect can be obtained. Included in.

1 ... Metal ring used in the present invention, 2 ... Main body, 3 ... Sub-circuit unit, 4 ... Metal ring of the prior art,
5 ... Magnetic flux passing through the metal ring, 6 ... Reverse induced current, 7 ... Magnetic flux generated by the reverse induced current,
8 ... Magnetic flux passing through the sub circuit, 9 ... Reverse induced current, 10 ... Magnetic flux on the main body side,
11 ... chamber, 12 ... upper shaft, 13 ... lower shaft, 14 ... raw material rod, 15 ... seed crystal,
16 ... high frequency coil, 17 ... aperture, 18 ... fusion zone, 19 ... crystallized semiconductor rod,
20 ... Dopant gas-doped nozzle, 21 ... Silicon single crystal growing device.

Claims (6)

A chamber, an upper shaft for attaching a raw material rod, a lower shaft for attaching a seed crystal, a high-frequency coil for melting the raw material rod, and a metal ring arranged above the high-frequency coil so as to surround the raw material rod. A silicon single crystal growing apparatus according to the FZ method, wherein the main body of the metal ring forms a closed circuit as a main circuit, and the metal ring is further provided with a closed circuit as a sub circuit. A silicon single crystal growing apparatus characterized by being. The silicon single crystal growing apparatus according to claim 1, wherein the metal ring is provided with two or more subcircuits. The silicon single crystal growing apparatus according to claim 1 or 2, wherein the metal ring is provided with a sub circuit above a plane formed by the main circuit of the metal ring. This is a method for producing a silicon single crystal by the FZ method. In a chamber, a raw material rod is attached to an upper shaft and a seed crystal is attached to a lower shaft, and then a metal ring is arranged above the high frequency coil so as to surround the raw material rod. Then, when the raw material rod is melted by the high frequency coil to produce a silicon single crystal, a closed circuit in which the main body of the metal ring is the main circuit is formed as the metal ring, and the metal ring is formed. , A method for producing a silicon single crystal, which comprises using a closed circuit as a sub-circuit. The method for producing a silicon single crystal according to claim 4, wherein the metal ring is provided with two or more subcircuits. The method for producing a silicon single crystal according to claim 4 or 5, wherein the metal ring is provided with a sub circuit above a plane formed by the main circuit of the metal ring.

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