JP5718617B2 - Silicon single crystal manufacturing apparatus, silicon single crystal manufacturing method, and induction heating coil processing method - Google Patents

Description

  The present invention relates to a silicon single crystal manufacturing apparatus, a silicon single crystal manufacturing method, and an induction heating coil processing method for manufacturing a silicon single crystal by an FZ (Floating Zone) method.

  Conventionally, a silicon single crystal manufacturing apparatus for manufacturing a silicon single crystal by the FZ method includes a reaction furnace for growing a silicon single crystal, a raw material holder for holding a raw silicon material as a raw material of the silicon single crystal, and raw silicon. An induction heating coil that partially heats the material to form a melting zone and solidifies the melting zone to grow a silicon single crystal, and a single crystal holder that holds the silicon single crystal are provided.

  The induction heating coil is a ring-shaped member that is formed mainly of copper or silver and surrounds the outer periphery of the raw silicon material (for example, see Patent Document 1). The single crystal manufacturing apparatus based on the FZ method described in Patent Document 1 serves as a heat source for forming a melting zone between at least a source silicon material and a silicon single crystal, and a chamber containing the source silicon material and the silicon single crystal. In order to prevent discharge between one or more of the raw material silicon material, silicon single crystal and melting zone and the induction heating coil, all or part of the surface of the induction heating coil A film of insulating material is formed.

JP 2006-169060 A

  Such an induction heating coil has a cooling water channel through which cooling water for cooling the induction heating coil flows inside the induction heating coil. Since copper or silver forming the induction heating coil is exposed in the cooling water channel, when the production of the single crystal is repeated, the cooling water channel is oxidized by the cooling water, and contaminants (for example, copper oxide) are generated in the cooling water channel. ) Is formed. When contaminants are formed in the cooling water channel, the heating of the raw material silicon material by the induction heating coil becomes unstable, which affects the quality of the silicon single crystal. For this reason, it has been necessary to replace the induction heating coil at a certain frequency and to wash with an acid in order to remove contaminants formed in the cooling water channel. In particular, as the raw material silicon material or silicon single crystal has a large diameter and a large heating amount, the influence of contaminants on the quality of the silicon single crystal becomes more significant, and the induction heating coil has to be frequently replaced.

  An object of the present invention is to provide a silicon single crystal manufacturing apparatus, a silicon single crystal manufacturing method, and an induction heating coil processing method capable of suppressing oxidation of a cooling water channel.

  A silicon single crystal manufacturing apparatus of the present invention includes a reaction furnace for growing a silicon single crystal by an FZ method, and a raw material holder for holding a raw silicon material that is housed in the reaction furnace and serves as a raw material for the silicon single crystal. An induction heating coil that is housed in the reactor and partially heats the raw silicon material to form a molten zone and solidifies the molten zone to grow a silicon single crystal. The heating coil is characterized in that cooling water for cooling the induction heating coil circulates and has a cooling water passage formed with a coating for preventing oxidation by the cooling water inside the induction heating coil.

  In the silicon single crystal manufacturing apparatus, the coating preferably has heat resistance and insulation.

  In the silicon single crystal manufacturing apparatus, the coating is preferably formed mainly of a resin material or an inorganic material.

  In the silicon single crystal manufacturing apparatus, the resin material preferably includes any one of polyimide resin, polytetrafluoroethylene, and polybenzimidazole.

  In the silicon single crystal manufacturing apparatus, the inorganic material is any one of various nitride films (for example, silicon nitride and aluminum nitride), various oxide films (for example, silicon oxide and aluminum oxide), and amorphous diamond. Preferably one is included.

  The silicon single crystal manufacturing method of the present invention is characterized in that a silicon single crystal is manufactured by the FZ method using the silicon single crystal manufacturing apparatus.

  The method of processing an induction heating coil according to the present invention is used for growing a silicon single crystal by the FZ method. A raw material silicon material is partially heated and melted to form a molten zone, and the molten zone is solidified. A method of processing an induction heating coil for growing crystals, an acid cleaning step for acid cleaning a cooling water passage formed inside the induction heating coil and through which cooling water for cooling the induction heating coil flows, and heat resistance and A coating liquid containing an insulating material is filled in the cooling water channel to form a film in the cooling water channel, and after the coating liquid is discharged from the cooling water channel, the film is removed. And a fixing step of fixing the film by drying.

  The method of processing an induction heating coil according to the present invention is used for growing a silicon single crystal by the FZ method. A raw material silicon material is partially heated and melted to form a molten zone, and the molten zone is solidified. A method of processing an induction heating coil for growing a crystal, wherein the induction heating coil has cooling water for cooling the induction heating coil flowing inside the induction heating coil by joining an upper coil and a lower coil. And a surface of the cooling water channel by a physical vapor deposition method or a chemical vapor deposition method in a state where the cooling water channel is exposed, and an acid cleaning step for acid cleaning the cooling water channel. A method for processing an induction heating coil, comprising: a film forming process for forming a film on the substrate; and a bonding process for bonding the upper coil and the lower coil.

  ADVANTAGE OF THE INVENTION According to this invention, the silicon single crystal manufacturing apparatus which can suppress the oxidation of a cooling channel, the manufacturing method of a silicon single crystal, and the processing method of an induction heating coil can be provided.

It is a side view which shows typically the silicon single crystal manufacturing apparatus 1 of this embodiment. FIG. 2A is a perspective view showing an outer shape of the induction heating coil 4, and FIG. 2B is a diagram showing a cross-sectional structure of the induction heating coil 4. It is a flowchart which shows one Embodiment of the processing method of the induction heating coil of this invention. It is a graph which shows the result of having measured the pollutant formed in the induction heating coil with the electron beam microanalyzer. It is a graph which shows the result of having measured the contaminant formed in the induction heating coil by X-ray diffraction.

  Hereinafter, an embodiment of a silicon single crystal manufacturing apparatus of the present invention will be described with reference to the drawings. FIG. 1 is a side view schematically showing a silicon single crystal manufacturing apparatus 1 of the present embodiment. As shown in FIG. 1, a silicon single crystal manufacturing apparatus 1 includes a reaction furnace 2, a raw material holder 3, an induction heating coil 4, a seed crystal holder 5, a single crystal weight holder 6, and a gas dope apparatus 7. And a control device 8.

  The reaction furnace 2 contains a raw material holder 3, an induction heating coil 4, a seed crystal holder 5, a single crystal weight holder 6, a raw material silicon material 9, a silicon single crystal 10, a melting zone 11 and a seed crystal 12, and FZ A silicon single crystal is grown by the method.

  The raw material holder 3 is a member that is accommodated in the reaction furnace 2 and holds the upper end portion of the raw material silicon material 9 that is a raw material of the silicon single crystal 10. The raw material holder 3 is attached to the upper shaft 21 located immediately above it. The upper shaft 21 is configured to be rotatable and configured to be movable in the vertical direction.

  The induction heating coil 4 is accommodated in the reaction furnace 2. The induction heating coil 4 partially heats the raw silicon material 9 to form a melting zone 11, and solidifies the melting zone 11 to grow a silicon single crystal 10. The induction heating coil 4 is a ring-shaped member that is formed mainly of copper or silver and surrounds the outer periphery of the raw material silicon material 9. “Made mainly of copper or silver” means, for example, the case where the entirety is formed of copper or silver, the majority is formed of copper or silver, and the remaining portion is a substance other than copper or silver. Including the case where it is formed. For example, in the induction heating coil 4, a metal member other than copper or silver may be used only for a portion used for connection to another member or a portion to be reinforced.

The seed crystal holder 5 is a member that holds and fixes the seed crystal 12 and the silicon single crystal 10 formed on the seed crystal 12. The seed crystal holder 5 is attached to the lower shaft 22 located immediately below the seed crystal holder 5. The lower shaft 22 is configured to be rotatable and configured to be movable in the vertical direction.
The single crystal weight holder 6 is a member that holds the lower tapered portion 10a in the grown silicon single crystal 10. The single crystal weight holder 6 receives most of the weight of the silicon single crystal 10 so that the weight of the silicon single crystal 10 is hardly applied to the seed crystal 12.

The gas dope device 7 includes a gas cylinder 71, a flow rate control valve 72, and a dope gas nozzle 73.
The control device 8 includes a CPU (Central Processing Unit), a storage device (both not shown) and the like, and controls the flow rate of the dopant gas supplied from the gas cylinder 71 by controlling the flow rate control valve 72.

The gas cylinder 71 contains a dopant gas in a high pressure state.
The flow control valve 72 opens and closes the valve according to the control of the control device 8.
The dope gas nozzle 73 is disposed in the vicinity of the induction heating coil 4 and supplies the dopant gas whose flow rate is controlled by the flow rate control valve 72 to the melting zone 11. By supplying the dopant gas to the melting zone 11 from the dope gas nozzle 73, the impurities are taken into the melting zone 11, that is, the silicon single crystal 10.

  In such a silicon single crystal manufacturing apparatus 1, the melting zone 11 is formed by heating the lower end portion of the raw silicon material 9 by the induction heating coil 4. Then, the silicon single crystal manufacturing apparatus 1 rotates the raw material silicon material 9 and the silicon single crystal 10 in the axial direction of the upper shaft 21 and the lower shaft 22 after the fusion zone 11 is fused to the seed crystal 12. Thus, the silicon single crystal 10 is grown from the melting zone 11.

  FIG. 2A is a perspective view showing an outer shape of the induction heating coil 4, and FIG. 2B is a diagram showing a cross-sectional structure of the induction heating coil 4. As shown in FIG. 2, the induction heating coil 4 includes a main body 40, a slit 41, and power supply terminals 42 and 43 that supply current to the induction heating coil 4.

  As shown in FIG. 2, the main body 40 has a substantially disk-shaped outer shape. The main body 40 has a cooling water channel 44 therein. The cooling water channel 44 is curved along the outer periphery of the main body 40 and has a substantially C shape (a shape that is substantially annular but has a cut and is not completely annular). Cooling water for cooling the induction heating coil 4 flows through the cooling water passage 44.

The slit 41 is formed in the main body 40 in the radial direction from the outer peripheral side to the inner peripheral side of the induction heating coil 4.
The power terminals 42 and 43 are formed symmetrically with respect to the slit 41 and supply current to the induction heating coil 4. In addition, the main body 40 of the induction heating coil 4 has an inlet portion for introducing cooling water from the outside of the induction heating coil 4 to the cooling water passage 44 and discharges the cooling water from the cooling water passage 44 to the outside of the induction heating coil 4. The exit part (all are not shown).

  The slit 41 is formed between the power supply terminal 42 and the power supply terminal 43. The slit 41 forms a cut in the substantially C-shaped cooling water channel 44.

As shown in FIG. 2B, a coating 45 is formed on the inner surface of the cooling water channel 44. The coating 45 is provided to prevent oxidation by cooling water.
The coating 45 preferably has heat resistance and insulation, and more preferably is formed mainly of a resin material or an inorganic material. Here, “formed mainly from a resin material or an inorganic material” means, for example, when the entire coating 45 is formed from a resin material or an inorganic material, and most of the coating 45 is a resin material or an inorganic material. The case where the coating film 45 contains a trace amount of other materials is also included. For example, most of the coating 45 may be formed of a resin material, and the coating 45 may contain a trace amount of additives. Moreover, since the induction heating coil 4 is heated to 100 ° C. or higher, it is more preferable to have heat resistance of 100 ° C. or higher.

  When the film 45 is formed mainly of a resin material, the film 45 preferably contains any one of polyimide resin, polytetrafluoroethylene, and polybenzimidazole.

  When the coating 45 is formed mainly of an inorganic material, the coating 45 is formed of various nitride films (for example, silicon nitride and aluminum nitride), various oxide films (for example, silicon oxide and aluminum oxide), or amorphous diamond. It is preferable that any one of these is included.

  Next, the processing method of the induction heating coil of this embodiment is demonstrated, referring FIG. FIG. 3 is a flowchart showing an embodiment of the method for processing an induction heating coil of the present invention. As shown in FIG. 3, the induction heating coil processing method of the present embodiment includes an acid cleaning step S1, a film forming step S2, and a fixing step S3.

(S1) Acid cleaning step First, hydrochloric acid is introduced from the inlet portion of the induction heating coil 4, acid cleaning is performed in the cooling water channel 44, and the cleaned hydrochloric acid is discharged from the outlet portion. Next, nitric acid is introduced from the inlet portion of the induction heating coil 4, acid cleaning is performed in the cooling water channel 44, and the cleaned nitric acid is discharged from the outlet portion. Finally, in order to remove the remaining acid, rinsing is performed by introducing pure water. Thereby, before forming the coating film 45 on the induction heating coil 4, contamination (such as an oxide film or cutting oil when manufacturing the induction heating coil) attached to the cooling water passage 44 can be removed.

(S2) Film Forming Step After passing through the acid cleaning step S1, a coating liquid containing a material having heat resistance and insulating properties is filled into the cooling water channel 44 from the inlet. Then, after a certain period, the coating liquid filled in the cooling water channel 44 is discharged from the outlet portion. The coating liquid remaining in the form of a film on the inner surface of the cooling water channel 44 forms a film 45.

(S3) Fixing Step After discharging the coating liquid from the cooling water channel 44, the coating film 45 is dried to fix the coating film 45 to the cooling water channel 44. When the coating 45 is dried, the induction heating coil 4 may be fixed by heating the induction heating coil 4 at a high temperature to dry the coating 45, or by drying the coating 45 at a normal temperature. Further, the method for forming a film is not limited to the formation of a film using a coating solution, and other appropriate methods can be selected. For example, in the manufacturing process of the induction heating coil 4, the cooling water passage 44 through which the cooling water for cooling the induction heating coil 4 flows is formed inside the induction heating coil 4 by joining the upper coil and the lower coil. In a state where the cooling water channel 44 of the induction heating coil 4 is exposed, a film is formed on the surface of the cooling water channel 44 by, for example, a PVD (physical vapor deposition) method, a CVD (chemical vapor deposition) method, or the like. Thereafter, the induction coil 4 may be manufactured by joining (for example, welding) the upper coil and the lower coil.

As described above, according to the silicon single crystal manufacturing apparatus 1, the silicon single crystal manufacturing method, and the induction heating coil processing method of the present embodiment, for example, the following effects can be obtained.
The silicon single crystal manufacturing apparatus 1 of the present embodiment holds a reaction furnace 2 that grows a silicon single crystal by the FZ method, and a raw material silicon material 9 that is housed in the reaction furnace 2 and serves as a raw material of the silicon single crystal 10. A raw material holder 3 and an induction heating coil that is housed in the reaction furnace 2 and that partially heats the raw material silicon material 9 to form a melt zone 11 and solidifies the melt zone 11 to grow a silicon single crystal 10. 4, the induction heating coil 4 has a cooling water passage 44 in which a cooling water for cooling the induction heating coil 4 flows and a coating 45 for preventing oxidation by the cooling water is formed inside the induction heating coil 4. .

  Therefore, according to the silicon single crystal manufacturing apparatus 1 of the present embodiment, since the cooling water channel 44 is oxidized by the cooling water and the formation of contaminants in the cooling water channel 44 is suppressed, the raw material by the induction heating coil 4 The heating of the silicon material 9 is stabilized, and the quality of the silicon single crystal 10 can be stabilized. Moreover, since it can suppress that a pollutant is formed in the cooling water channel 44, the exchange frequency of the induction heating coil 4 can be reduced, and the work time (cycle time) of the whole process which manufactures a silicon single crystal can be shortened. be able to.

  In addition, in the conventional induction heating coil, it is necessary to perform an acid cleaning step (for example, hydrochloric acid cleaning, nitric acid cleaning, etc.) for removing contaminants formed in the cooling water channel 44 every time the induction heating coil 4 is replaced. It was. On the other hand, according to the silicon single crystal manufacturing apparatus 1 of the present embodiment, the formation of contaminants in the cooling water channel 44 is suppressed by the coating 45 formed in the cooling water channel 44, and thus the above-described acid cleaning is performed. The process can be omitted and the cycle time can be shortened.

  In recent years, in order to improve the acquisition rate of silicon single crystals, the raw material silicon material has been increased in size, and the cycle time has been increased accordingly. According to the silicon single crystal manufacturing apparatus 1 of the present embodiment, the exchange frequency of the induction heating coil 4 can be reduced as described above, and the acid cleaning step for removing copper oxide can be omitted. An increase in cycle time associated with an increase in the size of the raw material silicon material can be suppressed.

  Moreover, the silicon single crystal 10 can be suitably obtained by manufacturing the silicon single crystal 10 by the FZ method using the silicon single crystal manufacturing apparatus 1 of the present embodiment.

  Further, the induction heating coil processing method of the present embodiment includes an acid cleaning step S1 in which the cooling water channel 44 formed inside the induction heating coil 4 and through which the cooling water for cooling the induction heating coil 4 flows is acid-washed, and heat resistance. In addition, the coating liquid containing the insulating material is filled in the cooling water channel 44 to form the coating film 45 in the cooling water channel 44, and after the coating liquid is discharged from the cooling water channel 44, the coating film And a fixing step S3 for fixing the coating 45 by drying 45. As a result, the coating 45 can be suitably formed in the cooling water channel 44.

  The silicon single crystal manufacturing apparatus, the silicon single crystal manufacturing method, and the induction heating coil processing method of the present invention have been described above, but the present invention is not limited to the above-described embodiments. For example, the induction heating coil 4 may have a shape other than the shape described above as long as it has a cooling water channel 44 through which cooling water flows.

[Identification of pollutants]
Contaminants were identified as follows.
Contaminants formed on the induction heating coil were identified using an electron probe microanalyzer (EPMA) and an X-ray diffraction (XRD).

  FIG. 4 is a graph showing the result of measuring the pollutant formed on the induction heating coil with an electron beam microanalyzer. As shown in FIG. 4, the peak indicated by a circle (●) is copper (Cu), the peak indicated by a triangle (▲) is oxygen (O), and the peak indicated by a square (■) is carbon ( C). From the measurement result of the pollutant by the electron beam microanalyzer shown in FIG. 4, it was found that main components of the pollutant are copper and oxygen. As a result of measuring and comparing the part without the contaminant as a reference, it was found that the part of the induction heating coil where the contaminant was formed was more oxidized than the part where the contaminant was not formed.

  FIG. 5 is a graph showing the results of measuring the contaminants formed on the induction heating coil by X-ray diffraction. As shown in FIG. 5, the peak indicated by a circle (◯) is copper (Cu), and the peak indicated by a triangle (Δ) is cupric oxide (CuO). In the measurement result by X-ray diffraction shown in FIG. 5, two peaks of cupric oxide were observed, so that the contaminant formed in the induction heating coil was identified as cupric oxide (CuO). . As a result of measuring the site without the contaminant as a reference, only the peak of copper, which is the base material of the induction heating coil, was detected. Therefore, it became further clear that the contaminated site was cupric oxide (CuO).

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these.

[Example]
The embodiment is an example in which a coating 45 is formed on the cooling water channel 44 of the induction heating coil 4.
First, hydrochloric acid was introduced from the inlet of the induction heating coil 4 to perform acid cleaning in the cooling water channel 44. After discharging hydrochloric acid from the cooling water channel 44, nitric acid was introduced from the inlet of the induction heating coil 44 to perform acid cleaning in the cooling water channel 44, and after washing, the nitric acid was discharged from the cooling water channel 44. Thereafter, pure water was introduced in the same manner for rinsing to remove the remaining acid.

  After the acid cleaning, a polyimide resin was used as a coating liquid (resin-based material), the coating liquid was filled in the cooling water channel 44, and a coating film 45 was formed in the cooling water channel 44. And after a fixed period, the coating liquid with which the cooling water channel 44 was filled was discharged | emitted from the exit part.

  After the coating liquid was discharged from the cooling water channel 44, the coating film 45 was dried at room temperature to fix the coating film 45 to the cooling water channel 44.

  The silicon single crystal 9 is grown by the silicon single crystal manufacturing apparatus 1 using the induction heating coil 4 having the coating 45 formed on the cooling water channel 44, and 15 dislocation-free silicon single crystals having a diameter of 200 mm and a length of 700 mm are continuously formed. And was able to get it.

[Comparative example]
The comparative example is an example in which the coating 45 is not formed in the cooling water channel 44 of the induction heating coil 4. Other configurations and evaluation directions are the same as those in the example.

  In the comparative example, when the silicon single crystal 9 is grown by the silicon single crystal manufacturing apparatus 1 using the induction heating coil 4 in which the coating 45 is not formed in the cooling water channel 44, no dislocation having a diameter of 200 mm and a length of 700 mm is obtained. Two silicon single crystals could be obtained continuously. However, when the silicon single crystal was manufactured by reusing the induction heating coil 4 without removing the contaminants formed in the cooling water channel 44, dislocation occurred in the silicon single crystal, resulting in a defective product. It became.

DESCRIPTION OF SYMBOLS 1 Silicon single crystal manufacturing apparatus 2 Reactor 3 Raw material holder 4 Induction heating coil 5 Seed crystal holder 6 Single crystal weight holder 7 Gas dope apparatus 8 Control device 9 Raw material silicon material 10 Silicon single crystal 11 Melting zone 12 Seed crystal 40 Main body 41 Slit 42 Power supply terminal 43 Power supply terminal 44 Cooling water channel 45 Coating

Claims (5)

A reactor for growing a silicon single crystal by the FZ method;
A raw material holder that is contained in the reaction furnace and holds a raw silicon material that is a raw material of the silicon single crystal;
An induction heating coil housed in the reaction furnace, partially heating the raw silicon material to form a melting zone, solidifying the melting zone and growing a silicon single crystal,
The induction heating coil, the cooling water is circulated to cool the induction heating coil, have a cooling channel coating to prevent oxidation by the cooling water is formed inside the induction heating coil,
The coating is formed mainly of a resin material,
The silicon single crystal manufacturing apparatus , wherein the resin material includes any one of polyimide resin, polytetrafluoroethylene, and polybenzimidazole .   The silicon single crystal manufacturing apparatus according to claim 1, wherein the coating has heat resistance and insulation. Method for manufacturing a silicon single crystal, characterized by manufacturing a silicon single crystal by the FZ method by using a silicon single crystal manufacturing apparatus according to claim 1 or 2. Induction heating coil processing method used for growth of a silicon single crystal by FZ method, in which a raw silicon material is partially heated and melted to form a molten zone, and the molten zone is solidified to grow a silicon single crystal Because
An acid cleaning step for acid cleaning a cooling water passage formed inside the induction heating coil and through which cooling water for cooling the induction heating coil flows;
A film forming step of filling the cooling water channel with a coating liquid containing a material having heat resistance and insulation, and forming a film in the cooling water channel;
And a fixing step of fixing the coating film by drying the coating film after discharging the coating liquid from the cooling water channel. Induction heating coil processing method used for growth of a silicon single crystal by FZ method, in which a raw silicon material is partially heated and melted to form a molten zone, and the molten zone is solidified to grow a silicon single crystal Because
The induction heating coil forms a cooling water channel through which cooling water for cooling the induction heating coil flows inside the induction heating coil by joining an upper coil and a lower coil. An acid cleaning step for cleaning;
In the state where the cooling water channel is exposed, a film forming step for forming a film on the surface of the cooling water channel by physical vapor deposition or chemical vapor deposition, and a bonding step for bonding the upper coil and the lower coil And a method for processing an induction heating coil.

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