JP5067406B2 - Silicon single crystal manufacturing method and silicon single crystal manufacturing apparatus - Google Patents

Description

  The present invention relates to a silicon single crystal manufacturing method and a silicon single crystal manufacturing apparatus in which gas in a furnace is exhausted by a water ring pump during manufacturing of a silicon single crystal.

  In recent years, silicon wafers used for discrete semiconductor devices and the like have N-type electrical characteristics and are highly doped with volatile dopants such as antimony (Sb), red phosphorus (P), and arsenic (As). There is an increasing demand for silicon wafers having a low resistance of 20 mΩcm or less. The manufacture of such a silicon single crystal doped with a volatile dopant is disclosed in Patent Document 1, for example.

  A water ring pump is usually used in an exhaust line for producing a single crystal using such a volatile dopant. In particular, the operation using red phosphorus as a dopant is accompanied by the risk of ignition. Therefore, an oil rotary pump and a dry pump are not suitable for exhaust, and a water ring pump is used to avoid the risk of ignition.

FIG. 6 is a schematic view when a water ring pump is used in the exhaust line of the silicon single crystal manufacturing apparatus.
As shown in FIG. 6, the water ring pump 64 connected to the furnace 61 is inferior to other types of vacuum pumps in terms of exhaust capacity (vacuum level), so an air ejector 63 is added to improve the vacuum level. Yes. For example, while flowing Ar gas, the gas in the furnace 61 is exhausted by the combination of the water ring pump 64 and the air ejector 63 to perform the decompression operation. The furnace pressure is controlled by a conductance valve 62.

  FIG. 7 is an explanatory diagram of the air ejector. When the gas sucked by the pump passes through the air ejector, the air ejector increases the gas flow velocity when the gas passes through the constricted part of the pipe and the pressure decreases. Air is sucked from other pipes connected to the part. With such a structure, the exhaust capacity of the water ring pump is improved.

JP 2008-280211 A

  However, oxides emitted from operations that use volatile dopants adhere to the inside of the air ejector, and especially when dopants are added and the operation time increases, oxides accumulate, and the exhaust capacity of the air ejector Decreases. When the exhaust capacity is lowered, the furnace pressure rapidly increases, and the furnace pressure cannot be controlled to the target operating pressure, so that a stable quality crystal cannot be obtained.

  The present invention has been made in view of the above-mentioned problems, and in manufacturing a silicon single crystal using a volatile dopant, prevents a reduction in exhaust capacity of an exhaust line due to oxides deposited on an air ejector. An object of the present invention is to provide a silicon single crystal manufacturing method and a silicon single crystal manufacturing apparatus capable of manufacturing a high-quality silicon single crystal with a high yield.

  In order to achieve the above object, the present invention provides a method of manufacturing a silicon single crystal doped with a volatile dopant by a CZ method, wherein the exhaust for exhausting a gas in a furnace during the manufacture of the silicon single crystal. As a line, two or more air ejectors connected in parallel, a switching valve installed before and after the air ejector, a sequencer for controlling opening and closing of the switching valve, and a subsequent stage of the air ejector are connected. The water ejector pump is provided, and the air ejector is switched during the production of the silicon single crystal by controlling the opening and closing of the switching valve by the sequencer during the exhaust of the gas in the furnace. A method for producing a silicon single crystal is provided.

In this way, by providing two or more air ejectors connected in parallel, the air ejector can be easily switched while exhausting during the production of a single crystal, and oxide is deposited in the air ejector. It is possible to effectively prevent the exhaust capability from being lowered. In addition, a switching valve installed before and after the air ejector is provided, and the switching valve is opened and closed by a sequencer, so that the switching valve is opened and closed in order, and air is introduced into the air ejector and exhausted. However, the air ejector can be switched by preventing the backflow of air or water seal water. Further, by exhausting with a water ring pump, it can be safely exhausted even in the production of a single crystal using a volatile dopant.
If the silicon single crystal manufacturing method of the present invention is as described above, a desired resistance doped with a volatile dopant while stabilizing the exhaust capability of the air ejector and preventing poor furnace pressure control by a simple method. It is possible to manufacture a silicon single crystal with a high yield.

At this time, the volatile dopant to be doped is preferably red phosphorus.
In this way, it is preferable to use the method for producing a silicon single crystal of the present invention when producing a single crystal in which oxides that are likely to adhere to the inside of the air ejector are discharged and flammable red phosphorus is doped.

At this time, it is preferable to switch the air ejector within 30 hours after the start of operation.
By switching the air ejector within 30 hours after the start of such operation, the air ejector can be switched before the inside of the air ejector is clogged and the exhaust capacity is reduced, and it is possible to easily and reliably prevent in-core pressure control failure.

At this time, switching of the air ejector is performed by detecting the furnace pressure, and automatically controlling the opening and closing of the switching valve by the sequencer when the detected furnace pressure exceeds a set pressure. It is preferable to perform switching.
In this way, by detecting the furnace pressure and automatically switching the air ejector when the detected furnace pressure exceeds the set pressure, it is easy to reduce the exhaust capacity due to clogging of the air ejector by detecting the furnace pressure. Therefore, the air ejector can be switched efficiently so as not to affect the operation.

At this time, it is preferable that the set pressure is a pressure that is 3 hPa higher than the target operating pressure in the furnace.
In this way, by setting the set pressure to be 3 hPa higher than the target operating pressure in the furnace, even if there is a fluctuation in the furnace pressure during switching of the air ejector, the total fluctuation in the furnace pressure does not affect the crystal quality. The air ejector can be switched within the range.

At this time, the switching valve is preferably opened and closed within 2 seconds for each switching valve.
In this way, the switching valve is opened and closed within 2 seconds for each switching valve, so that fluctuations in the furnace pressure during switching of the air ejector are kept within an allowable range, and air can flow back into the furnace. Can be prevented.

  The present invention is an apparatus for producing a silicon single crystal doped with a volatile dopant by a CZ method, and two or more air ejectors connected in parallel as an exhaust line for exhausting gas in the furnace, A switching valve installed before and after the air ejector, a sequencer for controlling the opening and closing of the switching valve, and a water ring pump connected to the rear stage of the air ejector are provided, and exhaust of gas in the furnace The silicon single crystal manufacturing apparatus is characterized in that the air ejector can be switched by controlling the opening and closing of the switching valve by the sequencer.

Thus, if the manufacturing apparatus is provided with two or more air ejectors connected in parallel, the air ejector can be easily switched while exhausting during the production of the silicon single crystal. It is possible to effectively prevent a reduction in exhaust capacity due to the deposition of oxide. In addition, a switching valve installed before and after the air ejector and a sequencer for controlling the opening and closing of the switching valve are provided, so that the switching valve can be opened and closed in order. Even while air is introduced and exhausted, the air ejector can be switched by preventing the backflow of air or water seal water. Further, by exhausting with a water ring pump, it can be safely exhausted even in the production of a single crystal using a volatile dopant.
With the silicon single crystal manufacturing apparatus of the present invention as described above, a silicon single crystal having a desired resistivity doped with a volatile dopant can be obtained while stabilizing the exhaust capability of the air ejector and preventing poor furnace pressure control. The device can be manufactured with a high yield.

The doped volatile dopant is preferably red phosphorus.
As described above, it is preferable to use the silicon single crystal manufacturing apparatus of the present invention for a single crystal manufacturing apparatus in which oxides that easily adhere to the inside of the air ejector are discharged and dope flammable red phosphorus.

The air ejector is preferably switched within 30 hours after the start of operation.
If the air ejector is switched within 30 hours after the start of the operation, the switching is performed before the oxide is deposited and the exhaust capacity of the air ejector is reduced. It becomes a device that can be prevented.

The switching of the air ejector detects the pressure in the furnace, and when the detected pressure in the furnace exceeds a set pressure, the switching of the switching valve is automatically controlled by the sequencer to switch the air ejector. It is preferable to do it.
In this way, if the furnace pressure is detected and the detected air pressure exceeds the set pressure, the air ejector is automatically switched. It becomes a device that can easily detect and switch the air ejector efficiently so as not to affect the operation.

The set pressure is preferably 3 hPa higher than the target operating pressure in the furnace.
In this way, if the set pressure is 3 hPa higher than the target operating pressure in the furnace, the air ejector should be switched within a range that does not affect the crystal quality even if the furnace pressure fluctuation during the air ejector switching is taken into account. Can do.

The switching valve is preferably opened and closed within 2 seconds for each switching valve.
In this way, if the switching valve is opened and closed within 2 seconds per switching valve, the pressure fluctuation in the furnace during the switching of the air ejector is suppressed within an allowable range, and the air flows back into the furnace. This is also reliably prevented.

  With the method and apparatus for producing a silicon single crystal according to the present invention as described above, when producing a silicon single crystal doped with a volatile dopant, the exhaust pressure of the air ejector is stabilized and the furnace pressure control is poor. While preventing, a crystal having a desired resistivity can be manufactured with a high yield.

It is the schematic which shows an example of the embodiment of the silicon single crystal manufacturing apparatus of this invention. It is a flowchart which shows the procedure of the switching of the air ejector of the silicon single crystal manufacturing apparatus of this invention. It is a graph which shows the relationship between the furnace pressure in Example 1, and a comparative example, and operation time. It is a graph which shows the relationship between the furnace pressure in Example 3, and switching time. It is a graph which shows the relationship by the opening / closing time of the switching valve | bulb of the furnace pressure in Example 2, and switching time. It is the schematic which shows an example of the conventional silicon single crystal manufacturing apparatus. It is explanatory drawing for demonstrating the structure of an air ejector.

Hereinafter, the silicon single crystal manufacturing method and silicon single crystal manufacturing apparatus of the present invention will be described in detail as an example of an embodiment with reference to the drawings. However, the present invention is not limited to this.
FIG. 1 is a schematic view showing an example of an embodiment of the silicon single crystal manufacturing apparatus of the present invention. FIG. 2 is a flowchart showing the procedure for switching the air ejector of the silicon single crystal manufacturing apparatus of the present invention.

  The silicon single crystal manufacturing apparatus 19 of the present invention shown in FIG. 1 has two or more air ejectors 12a and 12b connected in parallel and air ejectors 12a and 12b as an exhaust line 11 for exhausting the gas in the furnace 10. Switching valves 16a, 16b, 17a, 17b installed before and after the switch, a sequencer 21 for controlling opening and closing of the switching valves 16a, 16b, 17a, 17b, and a water seal connected to the rear stage of the air ejectors 12a, 12b A pump 13 is provided, and switching between the air ejector 12a and the air ejector 12b is performed by controlling the opening and closing of the switching valves 16a, 16b, 17a, and 17b by the sequencer 21 while the gas in the furnace 10 is being exhausted. It is something that can be done.

  In this way, if the manufacturing apparatus is provided with two or more air ejectors 12a and 12b connected in parallel, the air ejector 12a can be easily switched from the air ejector 12a to the air ejector 12b while exhausting during the production of the silicon single crystal. It can be performed, and it is possible to effectively prevent a reduction in exhaust capacity due to the accumulation of oxide inside the air ejector. In addition, the switching valves 16a, 16b, 17a, and 17b are arranged in order in order by providing the switching valves installed before and after the air ejector and the sequencer 21 for controlling the opening and closing of the switching valves. The air ejector can be switched from the air ejector 12a to the air ejector 12b, for example, by preventing the backflow of air or water-sealed water even when the air ejector is opened and closed and the air is introduced and exhausted. Moreover, by exhausting with the water ring pump 13, it can be safely exhausted even in single crystal production using a volatile dopant.

  Such air ejectors 12a and 12b, for example, as shown in FIG. 1, open the air introduction valves 15a and 15b and perform exhaust while introducing air, but improve the exhaust capability of the water seal pump 13. In addition to the function, it also has a function of preventing the backflow of water-sealed water into the furnace 10 when the water-sealed pump 13 is stopped. Therefore, in order to switch the air ejectors 12a and 12b safely without impairing the above functions, it is necessary to open the air introduction valves 15a and 15b and perform switching while continuing air introduction. For this reason, in the case of the apparatus of the present invention, the switching valves 16a, 16b, 17a, 17b are provided before and after the air ejectors 12a, 12b, and the sequencer 21 opens and closes the air so that the air enters the furnace 10. It is possible to reliably prevent backflow.

In such a silicon single crystal manufacturing apparatus 19 of the present invention, for example, a conductance valve 14 for controlling the furnace pressure and a backflow prevention valve 18 can be provided in front of the water seal pump 13. Further, a changeover switch 20 for giving an instruction to the sequencer 21 for switching the air ejectors 12a and 12b by opening and closing the changeover valves 16a, 16b, 17a and 17b can be provided.
Note that the number of air ejectors is not limited to two as long as they are connected in parallel, and three or more can be connected.

Next, the case where the silicon single crystal manufacturing method of the present invention is carried out using, for example, the silicon single crystal manufacturing apparatus of the present invention as shown in FIG. 1 will be described.
In the method for producing a silicon single crystal of the present invention, the silicon single crystal is pulled up from a silicon melt charged with a volatile dopant by a CZ (Czochralski) method.

  For example, a crucible having a diameter of 45 cm (18 inches) in the furnace 10 is charged with 40 to 80 kg of polycrystalline raw material, and the melting conditions are a target operating pressure in the furnace of 5 to 300 hPa, a gas flow rate of 10 to 300 l / min, A polycrystalline raw material can be melted at an electric power of 100 to 150 kW.

A dopant is introduced during melting, and the volatile dopant to be doped in the present invention is not particularly limited. For example, arsenic and antimony can be used, but red phosphorus is preferably used.
By exhausting with a water ring pump, it is possible to operate safely even with red phosphorus, and during the production of single crystals, oxides that are likely to deposit inside the air ejector are generated, which is also necessary for the discharge. The production method and production apparatus of the present invention capable of switching the air ejector are suitable.

In such silicon single crystal production, from the melting stage, Ar gas or the like is allowed to flow into the furnace 10, while the gas in the furnace 10 is exhausted by the exhaust line 11 to melt while controlling the furnace pressure. Then, the silicon single crystal is pulled up.
The conditions for pulling up the silicon single crystal by doping with red phosphorus are, for example, a gas flow rate of 10 to 300 l / min, a target operating pressure in the furnace of 5 to 300 hPa, a total length of 1000 to 1100 mm (straight barrel 600 to 700 mm), and a diameter of 200 mm. The silicon single crystal can be pulled up. In addition, said melting conditions and pulling conditions can be changed suitably.

In the apparatus of the present invention shown in FIG. 1, the gas is exhausted as described above, with the switching valves 16b and 17b being closed, and the switching valves 16a and 17a are fully opened to pass through the air ejector 12a (main line). Then, the gas in the furnace 10 is exhausted.
As shown in FIG. 2, the switching from the air ejector 12a to the air ejector 12b is performed by turning on the selector switch 20, and the sequencer 21 fully opens the switching valve 17b, fully opens the switching valve 16b, fully closes the switching valve 16a, and switches the switching valve. By opening and closing in the order of 17a fully closed, switching to the line (preliminary line) passing through the air ejector 12b is completed. By switching the switching valves 16a, 16b, 17a and 17b in such a procedure, switching from the air ejector 12a to the air ejector 12b can be performed while introducing air into the air ejectors 12a and 12b and exhausting. It can be done safely. Even during switching, the air introduction valves 15a and 15b of the air ejectors 12a and 12b are fully opened to introduce air in order to prevent backflow of the water seal water.

In this case, since the amount of oxide deposited inside the air ejector 12a varies depending on the amount of volatile dopant to be doped and the operation time, switching from the air ejector 12a to the air ejector 12b is appropriately performed before the furnace pressure largely fluctuates. For example, it is preferable to switch the air ejectors 12a and 12b within 30 hours after the start of operation.
Thus, if it is within 30 hours after the start of operation, switching can be performed before the oxide is deposited inside the air ejector to the extent that the exhaust capacity is lowered, and the in-furnace pressure control failure can be efficiently prevented. In this case, the starting point of operation can be the starting point of melting of the raw material or the starting point of pulling up of the single crystal. Capability reduction can be prevented.

Moreover, it is preferable to switch the air ejectors 12a and 12b when the furnace pressure is detected and the detected furnace pressure exceeds the set pressure.
In this way, by detecting the furnace pressure, it is possible to easily detect a reduction in exhaust capacity due to clogging of the air ejector, and when the detected furnace pressure exceeds the set pressure, the air ejector is automatically switched. If it is a thing, favorable furnace pressure control can be performed reliably.
This set pressure is not particularly limited, and is preferably a pressure 3 hPa higher than the target operating pressure in the furnace. Thereby, even if the pressure in the furnace changes during switching of the air ejector, it can be suppressed within an allowable range that does not affect the quality of the single crystal to be pulled up. Also, if the target operating pressure has a width of 3 hPa, the air ejector will automatically switch even if the furnace pressure has changed slightly from the target operating pressure due to other reasons, even though the exhaust capacity has not dropped. There is no impact on operability.

At this time, it is preferable that the switching valves 16a, 16b, 17a, and 17b be opened and closed within 2 seconds for each switching valve.
Thus, by opening and closing one switching valve within 2 seconds, the backflow of air can be effectively prevented. In addition, since the total time for switching the air ejector is within 8 seconds and the fluctuation of the pressure in the furnace during switching is within 2 hPa, the set pressure for automatically performing the switching as described above is 3 hPa higher than the target operating pressure in the furnace. By setting the pressure, the total fluctuation of the furnace pressure can be suppressed to within 5 hPa, switching can be performed smoothly, and the crystal quality and operability are not affected.

  With the method and apparatus for producing a silicon single crystal according to the present invention as described above, when producing a silicon single crystal doped with a volatile dopant, the exhaust pressure of the air ejector is stabilized and the furnace pressure control is poor. While preventing, a crystal having a desired resistivity can be manufactured with a high yield.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.
(Example 1, comparative example)
The silicon single crystal is manufactured using the silicon single crystal manufacturing apparatus (Example 1) of the present invention as shown in FIG. 1 and the conventional silicon single crystal manufacturing apparatus (comparative example) as shown in FIG. It was.
The silicon single crystal is manufactured by charging a crucible having a diameter of 45 cm (18 inches) with 70 kg of polycrystalline raw material, doping with red phosphorus, a gas flow rate of 40 l / min (target operating pressure in the furnace 40 hPa), and a gas flow rate of 100 l. A silicon single crystal having a diameter of 200 mm was manufactured under three conditions of / min (target operation pressure in the furnace 70 hPa) and gas flow rate 125 l / min (target operation pressure in the furnace 120 hPa).

At this time, in Example 1, the air ejector was switched in the procedure shown in FIG. 2 30 hours after the start of operation. Moreover, in the comparative example, it operated without replacing | exchanging an air ejector.
FIG. 3 shows the relationship between operating time and furnace pressure in Example 1 and Comparative Example.

  As can be seen from FIG. 3, in Example 1, the furnace pressure can be stably controlled even after 70 hours of operation, and in the comparative example, as the gas flow rate increases, the furnace pressure control becomes difficult in a shorter operation time. However, after 30 hours from the start of operation, the furnace pressure could not be controlled. All of the incompressible pressure control in the comparative example was caused by clogging of the air ejector.

(Example 2)
Using the silicon single crystal manufacturing apparatus of the present invention as shown in FIG. 1, the air ejector was switched while controlling the furnace pressure at a gas flow rate of 125 l / min (target operating pressure in the furnace of 120 hPa). At this time, the switching valve was opened and closed according to the procedure shown in FIG. 2, and the opening and closing time of one switching valve was performed under two conditions of 2 seconds and 5 seconds, respectively. FIG. 5 shows the relationship between the switching time and the furnace pressure at this time.

  As shown in FIG. 5 (a), when the switching valve was opened and closed in 2 seconds, the furnace pressure fluctuation during the air ejector switching was within 1 hPa, and the switching could be performed within a range that had no influence on the crystal quality. On the other hand, as shown in FIG. 5 (b), when the switching valve was opened and closed in 5 seconds, the pressure fluctuation in the furnace during the air ejector switching slightly increased to about 3 hPa.

(Example 3)
As in Example 1, except that the silicon single crystal was produced while controlling the furnace pressure at a gas flow rate of 125 l / min (target operation pressure in the furnace of 120 hPa), the furnace pressure was detected, and the target operation pressure (120 hPa) was detected. When the pressure reached 3 hPa higher (123 hPa), switching of the air ejector was started. The switching valve at the time of switching was opened and closed for 2 seconds per valve (total switching time was 8 seconds). The relationship between the switching elapsed time and the furnace pressure at this time is shown in FIG. In FIG. 4, the position of 0 on the switching time axis is the switching start time.

  As shown in FIG. 4, the change in the furnace pressure was within 5 hPa, including the change before switching, and the crystal quality was not affected.

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

10 ... furnace, 11 ... exhaust line, 12a, 12b ... air ejector,
13 ... Water ring pump, 14 ... Conductance valve,
15a, 15b ... air introduction valve,
16a, 16b, 17a, 17b ... switching valve,
18 ... Backflow prevention valve, 19 ... Silicon single crystal manufacturing device,
20 ... changeover switch, 21 ... sequencer.

Claims (12)

A method for producing a silicon single crystal doped with a volatile dopant by a CZ method,
Two or more air ejectors connected in parallel as an exhaust line for exhausting the gas in the furnace during the production of the silicon single crystal, a switching valve installed before and after the air ejector, and the switching valve A sequencer for controlling the opening and closing of the air ejector and a water ring pump connected to the rear stage of the air ejector, and controlling the opening and closing of the switching valve by the sequencer during the exhaust of the gas in the furnace, respectively A method for producing a silicon single crystal, wherein the air ejector is switched during the production of the silicon single crystal.   The method for producing a silicon single crystal according to claim 1, wherein the volatile dopant to be doped is red phosphorus.   The method for producing a silicon single crystal according to claim 1, wherein the air ejector is switched within 30 hours after the start of operation.   The switching of the air ejector is performed by detecting the pressure in the furnace and controlling the opening and closing of the switching valve automatically by the sequencer when the detected furnace pressure exceeds a set pressure. The method for producing a silicon single crystal according to claim 1, wherein the method is performed.   5. The method for producing a silicon single crystal according to claim 4, wherein the set pressure is set to a pressure 3 hPa larger than a target operation pressure in the furnace.   The method for producing a silicon single crystal according to any one of claims 1 to 5, wherein the switching valve is opened and closed within 2 seconds for each switching valve. An apparatus for producing a silicon single crystal doped with a volatile dopant by a CZ method,
As an exhaust line for exhausting the gas in the furnace, two or more air ejectors connected in parallel, a switching valve installed before and after the air ejector, and a sequencer for controlling opening and closing of the switching valve And a water ring pump connected to the subsequent stage of the air ejector, and switching the air ejector by controlling the opening and closing of the switching valve by the sequencer during the exhaust of the gas in the furnace. An apparatus for producing a silicon single crystal, characterized in that   The silicon single crystal manufacturing apparatus according to claim 7, wherein the volatile dopant to be doped is red phosphorus.   9. The silicon single crystal manufacturing apparatus according to claim 7, wherein the air ejector is switched within 30 hours after the start of operation.   The switching of the air ejector detects the pressure in the furnace, and when the detected pressure in the furnace exceeds a set pressure, the switching of the switching valve is automatically controlled by the sequencer to switch the air ejector. The silicon single crystal manufacturing apparatus according to any one of claims 7 to 9, wherein the apparatus is used.   The silicon single crystal manufacturing apparatus according to claim 10, wherein the set pressure is a pressure 3 hPa larger than a target operation pressure in the furnace. The silicon single crystal manufacturing apparatus according to any one of claims 7 to 11, wherein the switching valve is opened and closed within 2 seconds for each switching valve.

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