JP2009029659A - Single crystal pulling device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a single crystal pulling device and a method in which a means for avoiding hazard associated with damages in a cooling piping system is improved by improving the configuration of the cooling piping system constituting a cooler. <P>SOLUTION: The single crystal pulling device 1 is equipped with a cooler 10 for cooling a single crystal 32 during being pulled; wherein the cooler 10 includes a cooling piping system, the cooling piping system where cooling water is circulated is divided into a plurality of lineages along the pulling direction of the single crystal 32, and a top chamber 50 is provided with a rupture plate 60 that can respond to leaked water from one of the plurality of lineages in the cooling piping system. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a single crystal pulling apparatus and method. In particular, the present invention relates to a CZ method single crystal pulling apparatus and method including a cooler for cooling a pulling single crystal by the Czochralski method (hereinafter referred to as CZ method) and means for avoiding the danger caused by the cooler.

  Conventionally, a method of pulling a single crystal by the CZ method and a single crystal pulling apparatus by the CZ method are known. Furthermore, there is known a single crystal pulling apparatus provided with a cooler for cooling the single crystal pulled from the raw material melt when pulling the single crystal by the CZ method. By cooling the pulled single crystal using the cooler, crystal defects of the single crystal can be reduced and the pulling rate can be increased to increase the production efficiency.

Here, the cooler used by the CZ method is generally realized by a cooling piping system that passes cooling water around a single crystal. When such a cooling piping system is broken and cooling water leaks out, there is a possibility of damaging the entire single crystal pulling apparatus. Therefore, Patent Document 1 discloses a single crystal pulling apparatus in which a top chamber is provided with a safety valve (rupture plate) for releasing water vapor generated in the chamber to the atmosphere in case the cooling water leaks from the cooling piping system. Has been proposed. By working this safety valve (rupture plate), it is possible to prevent water vapor leaking from the cooling piping system from being lifted by the top chamber and splashing on surrounding workers.
JP 2000-344592 A

  However, the top chamber is packed with a lot of equipment such as a cooler lifting mechanism, a heat shielding plate lifting mechanism, a cooling pipe system for cooling the top chamber itself, and an observation window for observing the inside of the furnace. The space where the rupture plate can be installed is gradually limited. In addition, a solenoid that provides an appropriate magnetic field to the single crystal to be pulled up is disposed in the side surface of the chamber in close proximity, making it unsuitable as a location for the rupture plate. Furthermore, in the rupture plate installed on the side surface of the chamber, there is a positional relationship limit in order to effectively suppress the floating of the top chamber.

  Therefore, it is desired to provide a rupture plate that can be disposed in a limited space on the top chamber. Furthermore, it is desired to provide a rupture plate that can cope with an increase in the size of the cooler as the diameter of the single crystal to be pulled increases.

  Accordingly, the present invention has been made in view of such problems, and a single crystal pulling apparatus in which means for avoiding a risk associated with breakage of the cooling piping system is improved by improving the configuration of the cooler and the rupture plate. And to provide a method.

  More specifically, the present invention provides the following.

(1) A single crystal pulling apparatus for pulling a single crystal from a raw material melt in a crucible by a CZ method,
In a single crystal pulling apparatus equipped with a cooler for cooling the single crystal being pulled,
Including a cooling piping system constituting the cooler,
The cooling pipe system through which the cooling water flows is divided into a plurality of systems in the pulling direction of the single crystal,
A single crystal pulling apparatus, wherein a top chamber is provided with a rupture plate capable of handling leaked water from one of a plurality of cooling piping systems.

  According to such a configuration of the present invention, the single crystal pulling apparatus includes a cooler that cools the single crystal being pulled, and the cooler includes a cooling pipe system, and the cooling pipe system through which cooling water flows is provided. The top chamber is provided with a rupture plate configured to be divided into a plurality of systems in the pulling direction of the single crystal and capable of handling leakage water from one of the plurality of systems of the cooling piping system.

  Thus, the rupture plate has a size that can accommodate leaked water from one of the plurality of systems of the cooling piping system. Therefore, the rupture plate has a smaller size than before dividing the cooling piping system, and the degree of freedom in designing the installation location in the top chamber can be improved.

  As a result, the single crystal pulling apparatus can arrange a rupture plate having a smaller size in the top chamber.

  In this way, the single crystal pulling device requires only a small measure in the event that one of the cooling piping systems is damaged and the cooling water leaks into the device, and the degree of freedom in designing the location of the rupture plate can be reduced. Can be improved. In the cooling piping system divided into a plurality of systems, it is considered very unlikely that water leaks from the plurality of systems at the same time, so a small rupture plate is secured in the top chamber while ensuring a substantial safety margin. Can be arranged.

  The cooling piping system may be formed by bending a pipe into a coil shape, or may be a so-called jacket structure in which a plurality of members are formed by welding or the like.

  (2) Divide the piping size of the cooling piping system so that the temperature rise of the cooling water per system after the division of the cooling piping system is equal to or less than the temperature rise of the cooling water before the division. The single crystal pulling apparatus according to (1), wherein the single crystal pulling apparatus is configured to be thinner than before.

  According to such a configuration of the present invention, the single crystal pulling apparatus is configured such that the temperature rise of the cooling water per system after the division of the cooling pipe system is equal to or less than the temperature rise of the cooling water before the division. Thus, the piping size of the cooling piping system is configured to be narrower than before dividing.

  This makes it possible for the single crystal pulling apparatus to further reduce the water retention amount of the cooling piping system per system while maintaining the same cooling capacity as before the division, and to install a rupture plate having a smaller size. It can be arranged in the top chamber. In general, the cooling capacity of a cooler is proportional to the amount of cooling water that flows per unit time. The longer the cooling piping system is, the smaller the piping size is, the smaller the piping size is, the more cooling water flows through the cooling piping system due to pressure loss. Since the cooling piping system is divided, the length of the cooling piping system is shortened, and the degree of freedom in the direction of reducing the piping size is improved.

  As a result, the single crystal pulling device maintains the same cooling capacity as before the division, while the space occupied by the cooler in the device is reduced, and the created new space can be used for other purposes. It becomes. At the same time, it is possible to ensure a safety margin in the event of a rupture plate having a smaller size in the top chamber.

  (3) The single crystal pulling apparatus according to (1) or (2), wherein the cooler is movable in a pulling direction of the single crystal.

  According to such a configuration of the present invention, in the single crystal pulling apparatus, the cooler is movable in the pulling direction of the single crystal.

  Thus, the single crystal pulling apparatus can appropriately cool the pulled single crystal as required by moving the cooler in the pulling direction of the single crystal.

  (4) The single crystal pulling apparatus according to any one of (1) to (3), wherein the cooler is movable in the pulling direction of the single crystal independently for each system.

  According to such a configuration of the present invention, in the single crystal pulling apparatus, the cooler is movable in the pulling direction of the single crystal independently for each system.

  Thus, the single crystal pulling apparatus can appropriately cool the pulled single crystal as required by moving the cooler up and down independently for each system.

  (5) In any one of (1) to (4), a space for observing the inside of the furnace is provided between the cooling piping systems divided into a plurality of systems in the pulling direction of the single crystal. The single crystal pulling apparatus as described.

  According to such a configuration of the present invention, the single crystal pulling apparatus provides a space for observing the inside of the furnace between the cooling piping systems divided into a plurality of systems in the pulling direction of the single crystal.

Thereby, the single crystal pulling apparatus can observe the state in the furnace through the space provided between the coolers divided in the pulling direction of the single crystal.
By covering the space with the annular quartz glass 10c, it is possible to prevent disturbance of the gas flow in the furnace.

  (6) In a single crystal pulling apparatus that pulls a single crystal ingot having a diameter of about 300 mm or more, the cooling piping system is divided into two systems in the pulling direction of the single crystal ingot, and the height in the pulling direction is about 200 mm. The single crystal pulling apparatus according to any one of (1) to (5), wherein the diameter of the rupture plate is approximately 270 mm or less.

  (7) The single crystal pulling apparatus according to (6), wherein a piping size of the cooling piping system is approximately 12.7 mm or more and approximately 17.0 mm or less.

  (8) The single crystal pulling apparatus according to (7), wherein the length of the piping per system of the cooling piping system is set to about 11 m or less.

  According to the present invention, the rupture plate of the single crystal pulling apparatus has a size capable of accommodating leaked water from one of the plurality of systems of the cooling piping system. Therefore, the rupture plate has a smaller size than before dividing the cooling piping system, and the degree of freedom in designing the installation location in the top chamber can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  [Overall Configuration] A CZ method single crystal pulling apparatus 1 according to the present invention includes a crucible 30 for manufacturing and storing a silicon melt 31 in a chamber, which is a sealed container, in the same manner as a normal CZ method single crystal pulling apparatus. And a heater 21 for heating the crucible 30. In addition to this, as in a normal CZ method single crystal pulling apparatus, an electrode for supplying power to the heater 21, a crucible receiver for supporting the crucible 30, a pedestal for rotating the crucible 30, a heat insulating material, a melt receive, An inner cylinder is provided. In addition, this apparatus includes a heat shield 20 for shielding heat radiation to the silicon ingot 32 pulled up from the silicon melt 31 and the heater 21, and a cooler 10 disposed inside the heat shield 20. , Is provided. The top chamber 50 is provided with a rupture plate 60 as a rupture plate in order to prevent the top chamber 50 from being lifted by water vapor in the event that water leaks from the cooler 10. The rupture plate 60 discharges water vapor and suppresses damage to the apparatus when the pressure in the chamber exceeds a predetermined pressure due to generation of water vapor and the like, and the top chamber 50 is lifted so that surrounding workers can Accidents such as bathing can be prevented in advance.

  Such a CZ method single crystal pulling apparatus 1 pulls a single crystal while the pulling silicon ingot 32 and the crucible 30 rotate in the same direction or in the opposite direction, as in a normal CZ method single crystal pulling apparatus. Here, the crucible 30 is moved up and down by a lifter (not shown) provided at the lower part of the crucible 30. Unless otherwise specified, the crucible 30 moves up and down in such a manner that the crucible 30 is raised in accordance with the lowering of the silicon melt liquid level accompanying the pulling up of the silicon single crystal ingot.

  The CZ method single crystal pulling apparatus 1 according to the present invention is provided with an inert gas introduction / exhaust system that is normally provided in this type of CZ method single crystal pulling apparatus, although not particularly shown. Under such a system, the thermal shield 20 also has a function of adjusting the flow path of the inert gas. In this apparatus, a vacuum pump for exhausting the chamber 11 is connected.

  Further, the CZ method single crystal pulling apparatus 1 according to the present invention is provided with a solenoid for applying a magnetic field to the silicon melt 31. By applying a magnetic field to the silicon melt 31 by this solenoid, minute convection generated in the silicon melt 31 can be suppressed, and crystal defects can be reduced and stable pulling can be further promoted. become.

  [Cooler] In the CZ method single crystal pulling apparatus 1 according to the present invention, a cooler 10 constituted by piping through which cooling water flows is disposed inside the heat shield 20. As shown in FIG. 1, the cooler 10 is composed of a laminated body (cooling pipe stack) of piping surrounding the pulled silicon ingot 32, and cooling water is circulated through the piping. The cooling water is supplied through a supply pipe.

  FIG. 2 is a block diagram showing a coil portion of the cooler 10. Unlike the case of a single cooling piping system in the conventional cooler shown in FIG. 2A, the cooler 10 according to the present invention shown in FIGS. 2B and 2C includes an upper pipe 10a and a lower pipe. It is divided into two systems 10b. The upper pipe 10a and the lower pipe 10b are provided with independent supply pipes, and cooling water is also supplied independently. As a result, even if the coil portions have the same height, the length of the cooling piping system per system can be reduced to about half.

  By dividing the cooling piping system into two systems in this way, it becomes possible to shorten the length of the cooling piping system per system while maintaining the same cooling capacity. Furthermore, since the temperature rise of the cooling water can also be suppressed, the temperature on the downstream side can be suppressed lower than before the division, and safety is improved.

  Moreover, as shown in FIG.2 (c), the cooler 10 which concerns on this invention can be comprised so that an upper stage pipe 10a and a lower stage pipe 10b can move up and down independently. Further, using the gap formed between them, the inside of the furnace including the seed crystal 31a can be observed from a monitoring window provided in the upper chamber 50 or the like. It is possible to prevent the gas flow in the furnace from being disturbed by covering the gap with the annular quartz glass 10c.

  FIG. 3 is a block diagram showing the cooling piping system 100 of the CZ method single crystal pulling apparatus 1 according to an example of the preferred embodiment of the present invention. In FIG. 3, the upper pipe 10 a and the lower pipe 10 b are present in the chamber. The cooling water enters from the water supply side (left side in FIG. 3) of the cooling piping system 100, branches into two systems, enters the upper pipe 10a and the lower pipe 10b via the emergency shut-off valves 101a and 101b, and then exits the thermometer. It rejoins and recirculates through 104a and 104b, check valve or emergency shut-off valve 105a and 105b. The cooling piping system 100 can also be configured in three or more stages, and in that case, it can be realized by further branching the branching portion of FIG.

  [Parameter Adjustment] FIG. 4 shows the relationship between the design parameters of the cooler 10 and the rupture plate 60 of the CZ method single crystal pulling apparatus 1 according to an example of the preferred embodiment of the present invention. In order to obtain a predetermined endothermic amount (for example, 40 KW), it is advantageous that the height of the coil portion of the cooler 10 is higher (for example, 200 mm), but the amount of cooling water that may leak from the cooling piping system by that amount. (Water retention amount; amount of initial leakage water) increases, and the size of the rupture plate required in the event of an emergency increases. On the other hand, when the length of the pipe of the cooling piping system 100 is increased, the pressure loss in the piping increases, the cooling water becomes difficult to flow, and the temperature rise of the cooling water in the chamber increases. In addition, increasing the inner diameter of the pipe to suppress pressure loss also increases the outer diameter of the pipe, increasing the overall size of the cooler and increasing interference with other equipment in the chamber, which can be an obstacle to observation in the furnace. Become. Thus, when designing the cooler 10 and the rupture plate 60, it is necessary to search for the optimum value by adjusting the trade-off relationship of such parameters.

  FIG. 5 is a graph showing the temperature rise with respect to the cooling water flow rate by the CZ method single crystal pulling apparatus according to an example of the preferred embodiment of the present invention. FIG. 5B is an enlarged view of FIG. Here, if the required endotherm is 40 KW and the rising temperature threshold is 20 ° C., when realized with one cooling piping system, 40 KW per system is required, so the rising temperature is 20 ° C. or less. It is understood that a cooling water flow rate of about 29 L / min is necessary to achieve this. On the other hand, when the two systems are divided, it is sufficient that the heat absorption amount per system is 20 KW, so the required cooling water flow rate is about 14 L / min. Thus, by branching the cooling piping system into two systems, the required cooling water flow rate can be reduced by about 50%.

Table 1 shows the required cooling water flow rate when the rising temperature is 10 ° C. to 40 ° C. by the same calculation. As can be seen from this table, if the rising temperature is allowed to 40 ° C., 14.3 L / min water may be passed in one system. Moreover, when it accept | permits to 30 degreeC, it turns out that 19.1 L / min is required. On the other hand, when divided into two systems, it is necessary to pass water of 7.2 L / min and 9.6 L / min, respectively. Thus, it can be seen that even at an allowable temperature increase of 10 ° C. to 40 ° C., it is sufficient to divide the system into two systems so that approximately half the cooling water flow rate is sufficient.

  FIG. 6 is a graph showing the relationship between the inner diameter of the pipe and the water retention amount when the height of the coil portion of the cooler of the CZ method single crystal pulling apparatus according to an example of the preferred embodiment of the present invention is changed. The size of the rupture plate that can be arranged on the top chamber is about φ270 mm or less, and the water retention amount (that is, the amount of initial leakage water) that can be tolerated with this size is 3390 cc or less as shown in FIG. It can be seen that there is no problem if the inner diameter of the pipe is about 20 mm or less when the height of the coil portion is 100 mm (that is, when the coil portion is divided into two systems) in order to make it 3390 cc or less. On the other hand, when the height of the coil portion is 200 mm (that is, when realized with one system), it is understood that the inner diameter of the pipe needs to be 15 mm or less. Thus, the freedom degree of the design of the internal diameter of a pipe for making a water retention amount into a predetermined amount or less can be raised by using two cooling piping systems. As described above, if the inner diameter of the pipe can be increased, it is advantageous because the cooling water easily flows even when the length of the pipe is increased in relation to the pressure loss.

  FIG. 7 is a graph showing a simulation result of the outflow of steam at the time of water leakage when the size of the rupture plate of the CZ method single crystal pulling apparatus according to an example of the preferred embodiment of the present invention is changed. This is a simulation when a droplet having a diameter of 2 mm evaporates at an in-machine gas temperature of 800K as a precondition. More specifically, when the pipe breaks, the amount of water leaking into the chamber is the amount of initial leaked water (the amount of water remaining in the pipe) and the cooling water that flows in until the emergency shutoff valve works and stops. Total. Since a check valve is installed on the downstream side of the pipe, there is no back flow from the downstream side.

All of the initial leakage water becomes an aggregate of saturated droplets of a constant diameter in an infinitesimal time. The smaller the size of the droplet, the more the area that receives heat, and the faster the evaporation speed. A collection of saturated droplets of a constant diameter evaporates in a finite time with a pool boiling burnout heat flux according to the Kuterraladze equation. Further, the evaporation amount per unit area of the droplet surface area is obtained by dividing the burnout heat flux by the latent heat. Further, the evaporation amount of water vapor can be obtained by multiplying the evaporation amount per unit area by the total area of the droplets. The generated water vapor is heated to the in-machine gas temperature in an infinitesimal time, and the pressure at that time is calculated. In this manner, the simulation was performed to determine how much water vapor is released from the rupture plate 60, the top chamber 50, the lower rupture, and the vacuum pump, in which the calculated pressure is excreted in the top chamber 50.
If released from the rupture plate, there is no problem considering the installation location of the rupture plate, but when releasing from the top chamber, it is difficult to control the direction of water vapor release, and the operator may be nearby, It is extremely dangerous and it is necessary to install a rupture plate that is large enough to prevent discharge from the top chamber.

FIG. 7 is a simulation result when the rupture plate size is changed when the water retention amount is 2000 cc.
As can be seen from FIG. 7A, when the size of the rupture plate 60 disposed in the top chamber 50 is 114 mm, a large amount of water vapor is contained in the rupture plate 60 (TC rupture) and the lower rupture disposed in the top chamber 50. It can be seen that there is almost no discharge from the top chamber and vacuum pump. In this case, it is considered that the top chamber 50 does not float.

  On the other hand, as shown in FIG. 7B, when the size of the rupture plate 60 disposed in the top chamber 50 is 1 cm, a large amount of water vapor is discharged from the top chamber 50 and the rupture disposed in the top chamber 50. It can be seen that the discharge from the plate 60 (TC rupture) and the lower rupture is not sufficient. In this case, it is assumed that the top chamber 50 is lifted. That is, in this simulation, it can be seen that the size of the rupture plate 60 is not 100 mm, and 114 mm is necessary.

  FIG. 8 is a graph showing the required rupture plate size with respect to the initial leakage water amount of the CZ method single crystal pulling apparatus according to an example of the preferred embodiment of the present invention. Specifically, it is understood that the predetermined initial leakage water amount needs to be 3390 cc or less by repeatedly performing the simulation shown in FIG.

  FIG. 9 is a diagram illustrating an example of design of each parameter of the CZ method single crystal pulling apparatus according to an example of the preferred embodiment of the present invention. Specifically, on the assumption of the above calculation and simulation, a rupture installed in the top chamber with a coil portion height of 200 mm, a pipe length of 11000 mm or less, and a heat absorption amount of 40 KW was obtained. In order to set the plate diameter to 270 mm or less, the cooling water rising temperature to 20 ° C. or less, and the piping pressure loss to 60 KPa or less, the cooling water flow rate of 29 L / min is required when there is one cooling piping system. When the pressure loss is taken into consideration, it has been found that the inner diameter of the pipe needs to be 16.1 mm or more.

  Since the thickness of the cooler pipe is as thin as about 2 mm or more, the following danger increases when the pipe and the pipe are extended by welding to extend the length. That is, when build-up occurs inside the pipe of the welded portion, there is an increased risk that the prescribed amount of cooling water cannot be passed due to piping resistance. In addition, when the welding operation is insufficient and a portion having a thin wall is formed, there is an increased risk of cooling water leaking into the furnace. Therefore, it is ideal to have a structure with no welds. The maximum pipe length that can be prepared without a weld is about 11 m. If it exceeds this limit, it cannot be manufactured because the handling of pipes and handling during processing are restricted.

  Here, “equivalent to φ270 mm of the rupture plate” means that the pressure receiving area of water vapor is equivalent. Due to space restrictions on the top chamber, there is no problem in appropriately manufacturing the shape not only in a circular shape but also in an oval shape with a corresponding area or a combination of semicircles on both short sides of a rectangle. On the other hand, when the amount of water retained is taken into consideration, it is understood that the inner diameter of the pipe needs to be about 15 mm or less in one system. Then, it turns out that it is impossible to set the inner diameter of the pipe that satisfies the requirements of these parameters in one system.

  Next, when the cooling piping system is divided into two systems, the same calculation is performed, so that the cooling water flow rate needs to be 14 L / min, and when the pressure loss is taken into consideration, the inner diameter of the pipe needs to be 12.7 mm or more. I understand that there is. On the other hand, it is understood that the inner diameter of the pipe needs to be about 17 mm or less in the two systems when the water retention amount is taken into consideration. Then, it can be seen that, in the two systems, the design satisfying the requirements of these parameters can be performed by setting the inner diameter of the pipe to 12.7 mm or more and 17 mm or less.

  10 to 15 are graphs showing the relationship between the cooling water flow rate and the pressure loss of the CZ method single crystal pulling apparatus according to an example of the preferred embodiment of the present invention. As described above, it is necessary to design the pressure loss so as not to exceed the upper limit of 60 KPa. As shown in FIG. 10, when the inner diameter of the pipe is set to 16.7 mm, it can be seen that the same condition is satisfied even when the cooling water flow rate is 30 L / min. As shown in FIG. 11, it can be seen that even when the inner diameter of the pipe is 16.1 mm, the same condition is satisfied even when the cooling water flow rate is 30 L / min. As shown in FIG. 12, when the inner diameter of the pipe is 13.3 mm, in one system, the pressure loss exceeds 60 KPa at about 16 L / min or more, and the cooling water does not flow. Here, as shown in FIG. 5, in the case of one system, 29 L / min is required to obtain an endothermic amount of 40 KW, and it is understood that a realistic design is impossible. On the other hand, when divided into two systems, it can be seen that the pressure loss exceeds 60 KPa at about 22 L / min or more. Here, as shown in FIG. 5, in order to obtain an endothermic amount of 20 KW, a cooling water flow rate of about 14 L / min is required, so a realistic design is required between 14 L / min and 22 L / min. It turns out that it is possible.

  Similarly, as shown in FIG. 13, when the inner diameter of the pipe is 12.7 mm, a realistic design is impossible with one system, and with two systems, the cooling water flow rate is about 14 L / min. It turns out that realistic design is possible. Similarly, as shown in FIGS. 14 and 15, when the inner diameter of the pipe is 9.8 mm and 9.4 mm, respectively, it is understood that realistic design is impossible even with two systems.

[Cooler pipe design] Here, as shown in Table 2, based on the pipe dimensions according to Japanese Industrial Standards, if a thickness of 2 mm or more is secured in consideration of the risk of breakage, the pipe has an outer diameter of 21.7 mm. The inner diameter is 17.5 mm. Similarly, when the outer diameter is 17.3 mm, the inner diameter is 13.3 mm, and when the outer diameter is 13.8 mm, the inner diameter is 9.8 mm. In reality, the design is based on the pipe size.

Table 3 shows the maximum flow rates at the inner diameters of the pipes of one system and two systems when the cooler height is 200 mm. In addition, the flow rate is an integer value, and if it is calculated up to an integer, it can flow a little more. As can be seen from Table 3, if the internal system is 16.1 mm or more, it is possible to pass water of 30 L / min or more.

Table 4 shows the inner diameters of pipes that can be used for one system and two systems for each allowable temperature rise. As can be seen from Table 4, it can be seen that a pipe with a smaller inner diameter can be used when divided into two systems for the same allowable temperature rise than when one system is used. From this, it can be seen that the degree of freedom in design is improved in the pipe size when the system is divided into two systems.

Table 5 shows the relationship between the pipe diameter that can be practically designed and the initial leakage water. As can be seen from Table 5, when the target height of the coil portion is 200 mm, the amount of leaked water increases as the inner diameter of the pipe increases. Further, when the pipe length is up to 11 m, it can be seen that if it is realized with one system, the length of the pipe of the coil portion exceeds 11 m, so that a realistic design cannot be performed. On the other hand, by dividing into two systems, it can be seen that a realistic design is possible except for the one designed with a pipe inner diameter of 13.8 mm.

[Definition of symbols] The definitions of each symbol used here are as follows.

・・・・・・・・・・（１）

・・・・・・・・・・（２）

・・・・・・・・・・（３） [In-machine pressure balance model] Here, an in-machine pressure balance model is created. First, a case is modeled in which there is no leakage water, only purge gas is supplied, and the gas is discharged by a vacuum pump having a constant exhaust speed. In-machine pressure calculation is as follows.

(1)

(2)

(3)

・・・・・・・・・・（４）

・・・・・・・・・・（５）

・・・・・・・・・・（６） Since it is a one-component system with only purge gas, it is as follows.

(4)

(5)

(6)

・・・・・・・・・・（７） Here, when the discharge to the outside of the apparatus is performed only by the vacuum pump, the following occurs.

(7)

・・・・・・・・・・（８）

・・・・・・・・・・（９）

・・・・・・・・・（１０）

・・・・・・・・・（１１） The piping loss of the route to the vacuum pump is as follows.

(8)

(9)

... (10)

.... (11)

・・・・・・・・・（１２） The amount discharged by a vacuum pump with a constant pumping speed is as follows.

... (12)

  [Leaked Water Evaporation Model] Here, when leaked water enters the machine, the evaporation process can be modeled as follows.

・・・・・・・・・（１３）

・・・・・・・・・（１４）

・・・・・・・・・（１５） (1) It becomes an aggregate of saturated droplets having a fixed diameter in an infinitesimal time.
(2) A collection of saturated droplets having a constant diameter evaporates in a finite time by a pool boiling burnout heat flux according to the Kuteradze equation.
(3) The produced saturated steam is heated to the in-machine gas temperature in an infinitesimal time. Here, the leaked water mass and steam mass in the machine can be calculated as follows.

.... (13)

... (14)

... (15)

Here, the value of Q / L (evaporation amount per unit area in burnout heat flux) is as follows depending on the pressure from the water saturation table and the Kuteradze pool boiling burnout heat flux equation. give.

・・・・・・・・・（１６）

・・・・・・・・・（１７） Here, the in-machine partial pressure of steam is similar to the equations (2) and (3) as follows.

(16)

... (17)

・・・・・・・・・（１８）

・・・・・・・・・（１９）

・・・・・・・・・（２０） [Two-component system model] Next, the two-component system model integrates the input / output of the leaked water evaporation model part into the in-machine pressure balance model part to obtain the in-machine pressure balance considering the purge gas and the above two components. Using the output of the leakage water evaporation model part, (4) to (6) are rewritten as follows.

(18)

... (19)

.... (20)

・・・・・・・・・（２１）

・・・・・・・・・（２２） However, (20) is not used for the mass flow rate because a mass conservation model described later is calculated. Conversely, the following calculation is performed to feed back the result to the in-machine mass balance.

(21)

.... (22)

・・・・・・・・・（２３）

・・・・・・・・・（２４）

・・・・・・・・・（２５）

・・・・・・・・・（２６） [Rupture Plate Discharge Model] Discharge from the rupture plate and the top chamber (hereinafter collectively referred to as a rupture plate) can be modeled as follows.
(1) Solve the equation of motion of the rupture plate taking into account the in-machine pressure, dead weight, atmospheric pressure from the outside, and the spring deflection force (if any).
(2) The minimum displacement of the rupture plate is zero, and the maximum is the set value.
(3) At the minimum displacement position, the lower limit value of acceleration is set to zero, but the upper limit value is not set.
At the maximum displacement position, the upper limit value of acceleration is set to zero, but the lower limit value is not set.
Between the two, no lower limit upper limit value of acceleration is set.
(4) When the minimum or maximum displacement is reached, the speed is forced to zero (hard stop operation).
(5) The mass driven by the difference between the internal pressure and the atmospheric pressure flows out from the opening area due to the displacement under a constant resistance coefficient and incompressible process. The minimum value of the outflow velocity is zero, and the maximum value is the sound velocity.
The movement of the TC rupture plate is as follows under the restrictions (2) to (4). Under this limitation, the integral constant and interval cannot be expressed in mathematical formulas, so the integral is displayed indefinitely.

... (23)

... (24)

.... (25)

.... (26)

・・・・・・・・・（２７）

・・・・・・・・・（２８）

・・・・・・・・・（２９）

・・・・・・・・・（３０） Since the maximum displacement on the mechanism of the TC rupture plate is not defined, the displacement that corresponds to the opening area corresponding to the pressure receiving area is defined as the maximum displacement value. A top chamber is obtained as well.

... (27)

... (28)

... (29)

.... (30)

・・・・・・・・・（３１）

・・・・・・・・・（３２）

・・・・・・・・・（３３）

・・・・・・・・・（３４） The same applies to the lower rupture plate, but the spring load is taken into account when deriving the acceleration.

... (31)

.... (32)

.... (33)

.... (34)

・・・・・・・・・（３５）

・・・・・・・・・（３６）

・・・・・・・・・（３７） [Mass Conservation Model] The mass conservation model integrates the input and output of the rupture plate discharge model part into the in-machine pressure balance model part, and obtains the in-machine pressure balance considering the discharge amount from each rupture plate. Using the output of the rupture plate discharge model part, (7) is rewritten as follows.

... (35)

.... (36)

.... (37)

  All the above formulas are combined, the amount of water leakage into the machine is given as a function of time, and the top chamber displacement is solved at each time to obtain it as a function of time.

It is a block diagram which shows the CZ method single crystal pulling apparatus which concerns on an example of suitable embodiment of this invention. It is a block diagram which shows the coil part of the cooler of the CZ method single crystal pulling apparatus which concerns on an example of suitable embodiment of this invention. It is a block diagram which shows the cooling piping system of the CZ method single crystal pulling apparatus which concerns on an example of suitable embodiment of this invention. It is a figure which shows the correlation of each parameter of the CZ method single crystal pulling apparatus which concerns on an example of suitable embodiment of this invention. It is a graph which shows the temperature rise with respect to the cooling water flow rate by the CZ method single crystal pulling apparatus which concerns on an example of suitable embodiment of this invention. It is a graph which shows the relationship between the internal diameter of a pipe when the height of the coil part of the cooler of the CZ method single crystal pulling apparatus which concerns on an example of suitable embodiment of this invention, and a water retention amount. It is a graph which shows the simulation of the outflow of the vapor | steam at the time of water leakage at the time of changing the size of the rupture board of the CZ method single crystal pulling apparatus which concerns on an example of suitable embodiment of this invention. It is a graph which shows the size of the required rupture board with respect to the initial amount of leaked water of the CZ method single crystal pulling apparatus which concerns on an example of suitable embodiment of this invention. It is a figure which shows an example of the design of each parameter of the CZ method single crystal pulling apparatus which concerns on an example of suitable embodiment of this invention. It is a graph which shows the relationship between the cooling water flow rate and pressure loss of the CZ method single crystal pulling apparatus which concerns on an example of suitable embodiment of this invention. It is a graph which shows the relationship between the cooling water flow rate and pressure loss of the CZ method single crystal pulling apparatus which concerns on an example of suitable embodiment of this invention. It is a graph which shows the relationship between the cooling water flow rate and pressure loss of the CZ method single crystal pulling apparatus which concerns on an example of suitable embodiment of this invention. It is a graph which shows the relationship between the cooling water flow rate and pressure loss of the CZ method single crystal pulling apparatus which concerns on an example of suitable embodiment of this invention. It is a graph which shows the relationship between the cooling water flow rate and pressure loss of the CZ method single crystal pulling apparatus which concerns on an example of suitable embodiment of this invention. It is a graph which shows the relationship between the cooling water flow rate and pressure loss of the CZ method single crystal pulling apparatus which concerns on an example of suitable embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 CZ method single crystal pulling apparatus 10 Cooler 10a Upper stage pipe 10b Lower stage pipe 10c Quartz glass 20 Heat shielding board 21 Heater 30 Crucible 31 Silicon melt 31a Seed crystal 32 Silicon ingot 40 Motor 41 Encoder 42 Lifting block 50 Top chamber 60 Rupture board

Claims (8)

A single crystal pulling apparatus for pulling a single crystal from a raw material melt in a crucible by a CZ method,
In a single crystal pulling apparatus equipped with a cooler for cooling the single crystal being pulled,
Including a cooling piping system constituting the cooler,
The cooling pipe system through which the cooling water flows is divided into a plurality of systems in the pulling direction of the single crystal,
A single crystal pulling apparatus, wherein a top plate is provided with a rupture plate capable of handling leakage water from one of a plurality of systems of the cooling piping system.   The pipe size of the cooling piping system is made thinner than before the division so that the temperature rise of the cooling water per system after the division of the cooling pipe system is equal to or less than the temperature rise of the cooling water before the division. The single crystal pulling apparatus according to claim 1, wherein the single crystal pulling apparatus is configured.   The single crystal pulling apparatus according to claim 1, wherein the cooler is movable in a pulling direction of the single crystal.   The single crystal pulling apparatus according to any one of claims 1 to 3, wherein the cooler is movable in the pulling direction of the single crystal independently for each system.   The single unit according to any one of claims 1 to 4, wherein a space for observing the inside of the furnace is provided between the cooling piping systems divided into a plurality of systems in the pulling direction of the single crystal. Crystal pulling device.   In a single crystal pulling apparatus that pulls a single crystal ingot having a diameter of approximately 300 mm or more, the cooling pipe system is divided into two systems in the pulling direction of the single crystal ingot, and the height in the pulling direction is approximately 200 mm or more. The single crystal pulling apparatus according to any one of claims 1 to 5, wherein a diameter of the rupture plate is approximately 270 mm or less.   The single crystal pulling apparatus according to claim 6, wherein a pipe size of the cooling pipe system is set to approximately 12.7 mm or more and approximately 17.0 mm or less.   The single crystal pulling apparatus according to claim 7, wherein the length of the pipe per one line of the cooling pipe system is set to about 11 m or less.

Images