JP4983354B2 - Single crystal growth equipment - Google Patents

Description

  The present invention relates to a single crystal growth apparatus used for manufacturing a silicon single crystal, which is the most basic substrate material in semiconductor device manufacturing, and more particularly to a single crystal growth apparatus for growing a silicon single crystal by the Czochralski method.

  There are various methods for producing a silicon single crystal (hereinafter, sometimes simply referred to as “single crystal”). Among them, the Czochralski method (hereinafter, referred to as “CZ method”) is common. . In the production of a single crystal by the CZ method, a seed crystal is immersed in a silicon melt stored in a quartz crucible in a furnace in a reduced-pressure atmosphere, and the seed crystal is rotated while rotating the crucible and the seed crystal from this state. Pull up gradually. As a result, a silicon single crystal is grown below the seed crystal to obtain a substantially cylindrical single crystal.

  In pulling a single crystal by such a CZ method, it is known that the defect distribution in the crystal cross section depends on the crystal growth rate, that is, the pulling rate. As the pulling speed is increased, the ring-shaped OSF generation region moves to the outer peripheral portion, and is finally excluded outside the crystal effective portion. Conversely, by lowering the pulling speed, the ring-shaped OSF generation region moves to the crystal center, and finally disappears at the center.

  Both the outside and inside of the OSF generation area are defect generation areas, but the types of defects are different between the outside and the inside. Further, it is known that when the pulling speed is increased, the productivity is naturally improved and the defects are further miniaturized. For these reasons, as one direction in crystal growth, speeding up of the pulling has been pursued.

  As a technique for realizing high-speed pulling, arrangement of a heat shield is known. The heat shield is an inverted frustoconical cylindrical heat insulating member provided so as to surround the periphery of the single crystal, and mainly radiates heat from the melt in the crucible and the heater disposed outside the crucible. Block it. Thereby, since heating of the single crystal pulled up from the melt is suppressed, cooling of the single crystal is promoted as a result, and the pulling rate is increased.

  Furthermore, recently, a technique for arranging a cylindrical cooling body that is forcibly water-cooled inside the heat shield has also attracted attention (see, for example, Patent Document 1). By providing a cylindrical cooling body that circulates cooling water inside the heat shield so as to surround the periphery of the single crystal, cooling of the single crystal particularly in the high-temperature part is further promoted, and the pulling speed is increased. Further speedup is achieved.

  By the way, in the growth of a single crystal by such a CZ method, when an unplanned drop or the like of the single crystal occurs, various hot zone components such as a crucible (such as a heat shield and a cooling body) are not damaged. can not deny. However, among the components that increase the pulling speed, damage to the heat shield does not cause a significant problem.

  However, if the cooling body is damaged, a serious accident may occur. Due to the breakage of the cooling body, the cooling water flowing through the inside of the cooling body leaks into the furnace body, and when the leaked cooling water comes into contact with a melt or the like having a very high temperature, vaporization occurs at once and the furnace body The pressure rises rapidly. In other words, it can cause a steam explosion. Further, even when the cooling body is not damaged, the cooling water may spontaneously leak due to aging or the like. In this case, there is a concern of the same steam explosion.

  For such problems in safe operation, in the conventional single crystal growth apparatus, the flow rate of the cooling water flowing into the cooling body and the flow rate of the cooling body flowing out of the cooling body are respectively measured with a flow meter. The abnormal leakage of the cooling water is determined based on only the flow rate difference (see, for example, Patent Document 2). This is because when there is no water leakage in the cooling body, the amount of cooling water flowing into the cooling body matches the amount of cooling water flowing out of the cooling body, while when water leakage occurs in the cooling body, This is because the outflow amount from the cooling body is reduced as compared with the inflow amount. With such a single crystal growing apparatus, it is possible to detect water leakage from the cooling body during operation, and as a result, appropriate measures can be taken before a serious accident occurs.

JP-A-11-92272 JP 2002-104895 A

  However, in the conventional single crystal growth apparatus described above, in determining the abnormal leakage of cooling water, there is actually a flow rate difference in the flow of cooling water into and out of the cooling body even though the cooling body is healthy and there is no leakage. As a result, it may be misjudged that there is water leakage. This is because the water supply pressure of the cooling water to the cooling body becomes unstable depending on the capacity of the water supply pump, the operating condition, etc., or the output from the flowmeter is affected by flying noise. When such a misjudgment occurs, the operation is interrupted in order to confirm the presence or absence of water leakage, which hinders stable operation.

  Therefore, the present invention has been made in view of the above problems, and is excellent in stable operability capable of detecting water leakage from the cooling body with high accuracy while increasing the pulling speed using the cooling body. An object of the present invention is to provide a single crystal growth apparatus.

  In order to achieve the above object, a single crystal growth apparatus according to the present invention includes the following configuration in a single crystal growth apparatus for growing a single crystal from a raw material melt in a furnace by a CZ method. A cooling body that surrounds a single crystal grown from a raw material melt in a furnace and is cooled by cooling water flowing through the inside to cool the single crystal. An inflow side flow meter for detecting a flow rate of the cooling water flowing into the cooling body. An outflow side flow meter for detecting a flow rate of the cooling water flowing out of the cooling body. A pressure gauge for detecting the pressure in the furnace body. The flow rate difference between them is calculated from the detection values of the inflow side flow meter and the outflow side flow meter, the pressure fluctuation per unit time is calculated from the detection value of the pressure gauge, and based on the flow rate difference and the pressure fluctuation. A control unit for determining whether or not the cooling water leaks.

  With such a configuration, the leakage of the cooling water from the cooling body is determined based on the flow rate difference and the pressure fluctuation, but the flow rate difference and the pressure fluctuation are separate phenomena caused by the water leakage. The determination of water leakage based on both is highly accurate.

Here, based on the practicality, wherein, within a predetermined period of less than 5 seconds 1 seconds, when the flow rate difference and the pressure variation exceeds a preset threshold, you determined that there leakage .

  Further, from the viewpoint of preventing a serious accident, a water supply pipe connected to the cooling water inlet to the cooling body and provided with the inflow side flow meter in the path, and the cooling body from the cooling body A drain pipe connected to the cooling water outlet and provided with the outflow side flow meter in the path, a branch pipe branched from the drain pipe and opened to the outside, and water supply for opening and closing the path of the water supply pipe A pipe valve, a drain pipe valve that opens and closes a path of the drain pipe downstream from a branch point to the branch pipe, and a branch pipe valve that opens and closes the path of the branch pipe, and the control unit includes: When it is determined that there is water leakage, it is preferable that the water supply pipe valve and the drain pipe valve are switched from the open state to the closed state, and the branch pipe valve is switched from the closed state to the open state.

  According to the single crystal growing apparatus of the present invention, water leakage from the cooling body can be detected with high accuracy, and stable operation can be performed.

  Hereinafter, an embodiment of a single crystal growth apparatus of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a longitudinal sectional view showing a configuration of a single crystal growing apparatus according to an embodiment of the present invention, and FIG. 2 is a transverse sectional view of the single crystal growing apparatus. As shown in FIGS. 1 and 2, the single crystal growing apparatus is generally called a pulling furnace, and includes a cylindrical main chamber 1 and a pull chamber 2 as a furnace body constituting an outer shell. The pull chamber 2 is smaller in diameter and longer than the main chamber 1 and is coaxially disposed on the main chamber 1.

  A crucible 3 is arranged in the center of the main chamber 1. The crucible 3 has a double structure, and is composed of an inner quartz crucible filled with polycrystalline silicon and a graphite support crucible fitted outside. The crucible 3 is supported on a support shaft (not shown) called a pedestal, and rotates in the circumferential direction or moves up and down in the axial direction according to the rotational drive and lift drive of the support shaft.

  On the outer side of the crucible 3, a resistance heating type heater 4 is concentrically arranged so as to surround the crucible 3, and on the further outer side, a heat insulating cylinder 5 is arranged along the inner surface of the main chamber 1. The heater 4 melts the polycrystalline silicon filled in the crucible 3, whereby the silicon melt 6 is stored in the crucible 3.

  On the other hand, above the crucible 3, a wire 7 as a pulling shaft is suspended through the center portion in the pull chamber 2. The wire 7 is rotationally driven by a pulling mechanism provided at the upper part of the pull chamber 2 and is driven up and down in the axial direction. A seed chuck for holding the seed crystal is attached to the lower end of the wire 7. The seed crystal held in the seed chuck is immersed in the melt 6 in the crucible 3, and the wire 7 is driven to gradually raise the seed crystal while rotating the seed crystal. Will grow.

  Above the crucible 3, a substantially cylindrical heat shield 9 is provided concentrically near the melt 6 in the crucible 3 so as to surround the single crystal 8. The heat shield 9 is made of graphite and plays a role of blocking radiant heat from the melt 6 and the heater 4 in the crucible 3. In order to effectively exhibit the heat shielding effect, the heat shielding body 9 gradually increases in diameter from the lower side to the upper side, and the lower part thereof is inserted into the crucible 3 and above the melt 6 in the crucible 3. A preferred inverted frustoconical shape (tapered shape) is preferred.

  A substantially cylindrical cooling body 10 is provided concentrically inside the heat shield 9. The cooling body 10 is made of a copper-based metal having good thermal conductivity, and a water passage for circulating cooling water is formed therein. A water supply pipe 14 is connected to the cooling body 10 at the inlet of the water passage, and a drain pipe 15 is connected to the outlet of the water passage. The water supply pipe 14 and the drain pipe 15 are also made of a copper-based metal. Cooling water flows into the cooling body 10 through the water supply pipe 14, and the inflowing cooling water flows out of the cooling body 10 through the water passage and is discharged through the drain pipe 15. Thus, the cooling body 10 is forcibly cooled by the cooling water flowing through the inside.

  The cooling body 10 is disposed in the lower part of the heat shield 9 and surrounds the high temperature portion of the single crystal 8, particularly immediately after solidification, thereby promoting the cooling of the high temperature portion. The cooling body 10 also has a tapered shape in which the diameter is gradually increased from the bottom to the top as in the case of the heat shield 9. The water supply pipe 14 and the drain pipe 15 are welded in a state where no load is applied to the cooling body 10.

  The cooling body 10 is supported in the furnace body by a plurality of support arms 13 arranged radially around a pulling axis in the furnace body. The support arm 13 is a substantially inverted L-shaped bar that extends horizontally from the upper inner surface of the main chamber 1 toward the center of the furnace body and curves downward from the middle. The cooling body 10 has an upper edge portion. The support arms 13 are detachably connected to the tip portions of the support arms 13 with bolts or the like. Each support arm 13 is made of stainless steel here, and is forcibly cooled by water flowing through a system different from the cooling body 10.

  The main chamber 1 is connected to a vacuum exhaust pipe 11 connected to a vacuum pump (not shown). By driving the vacuum pump, the air inside the furnace body is exhausted through the vacuum exhaust pipe 11, and the furnace body is brought into a reduced pressure atmosphere. A butterfly valve (not shown) is provided in the path of the vacuum exhaust pipe 11, and the pressure in the furnace body is adjusted according to the degree of opening and closing of the butterfly valve. The butterfly valve is driven by a command from the control unit 22 shown in FIG.

  A purge gas introduction pipe (not shown) for introducing an inert gas such as Ar gas into the furnace body is connected to the upper portion of the pull chamber 2. An inert gas is supplied into the furnace body through a purge gas introduction pipe, and the furnace body is brought into an inert gas atmosphere under reduced pressure. The amount of inert gas introduced into the furnace is adjusted by the mass flow provided in the path of the purge gas introduction pipe. The mass flow is driven by a command from the control unit 22 shown in FIG.

  The main chamber 1 is provided with a pressure gauge 12 for detecting the pressure inside the furnace body. However, the detection of the in-furnace pressure is not limited to this, and any pressure that can substantially detect the in-furnace pressure may be used. For example, the gas pressure discharged outside the furnace may be detected.

  FIG. 3 is a system diagram of a water leakage monitoring system in the single crystal growing apparatus. As shown in FIG. 3, the water supply pipe 14 is provided with a first flow meter 17 and an automatic first on-off valve 19 in the path. The first flow meter 17 detects the flow rate of the cooling water flowing into the cooling body 10 through the water supply pipe 14. An ultrasonic type can be applied as the first flow meter 17. The first on-off valve 19 opens the path of the water supply pipe 14 in the open state, and blocks the path of the water supply pipe 14 in the closed state. Here, the first flow meter 17 is provided with a pipe length within 3 m from the cooling body 10, and the first on-off valve 19 is provided on the upstream side of the first flow meter 17. In the upstream area of the water supply pipe 14, a water supply pump (not shown) for sending cooling water is disposed.

  Similarly, the drain pipe 15 is provided with a second flow meter 18 and an automatic second on-off valve 20 in the path. The second flow meter 18 detects the flow rate of the cooling water flowing out from the cooling body 10 through the drain pipe 15. An ultrasonic type can be applied as the second flow meter 18. The second on-off valve 20 opens the path of the drain pipe 15 in the open state and blocks the path of the drain pipe 15 in the closed state. The second flow meter 18 here is provided with a pipe length within 3 m from the cooling body 10, and the second on-off valve 20 is provided on the downstream side of the second flow meter 18.

  A branch pipe 16 branched from between the second flow meter 18 and the second on-off valve 20 is attached to the drain pipe 15. The branch pipe 16 is equipped with a dedicated automatic third on-off valve 21 in the path. The third on-off valve 21 opens the path of the branch pipe 16 in the open state and blocks the path of the branch pipe 16 in the closed state. The downstream end of the branch pipe 16 is opened outside the furnace body.

  The first flow meter 17 and the second flow meter 18 are connected to the control unit 22, and the control unit 22 receives signals relating to the flow rates L 1 and L 2 detected by the first flow meter 17 and the second flow meter 18, respectively. . Further, the pressure gauge 12 is connected to the control section 22, and the control section 22 receives a signal related to the pressure P in the furnace detected by the pressure gauge 12. The first on-off valve 19, the second on-off valve 20, and the third on-off valve 21 are operated by commands from the control unit 22.

  Next, an operation example of crystal growth using such a single crystal growing apparatus will be described.

  The crucible 3 is charged with 100 kg of polycrystalline silicon raw material, and then the furnace is filled with an Ar atmosphere of 200 Pa. The polycrystalline silicon raw material in the crucible 3 is melted by the heater 4 provided outside the crucible 3, and a single crystal 8 having a diameter of 200 mm is grown thereunder using a seed crystal of 100 orientation.

  At this time, the crucible 3 is gradually raised according to crystal growth so that the liquid level of the melt 6 in the crucible 3 is maintained constant. Further, the crucible 3 is rotated in the same direction as the rotation direction of the single crystal 8 or in the opposite direction.

  In normal operation, both the first on-off valve 19 and the second on-off valve 20 are opened, while the third on-off valve 21 is closed. If it does so, a cooling water will distribute | circulate to the cooling body 10 through the water supply pipe 14 and the drain pipe 15 with which the path | route was opened, and the cooling body 10 will be forcedly cooled. Thereby, the high-temperature part of the single crystal 8 particularly immediately after solidification is forcibly cooled. As a result, the pulling speed of the single crystal 8 was 2 mm / min or more. Incidentally, the achieved pulling speed when the cooling body 10 was not used was about 1 mm / min. In addition, since the path | route of the branch pipe 16 is interrupted | blocked, a cooling water does not distribute | circulate.

  Here, the operation of the water leakage monitoring system performed during the operation will be described below.

  FIG. 4 is a flowchart showing the operation of the water leakage monitoring system in the single crystal growing apparatus. As shown in FIG. 4, first, at step # 5, the control unit 22 sends a signal related to the inflow flow rate L1 of the cooling water from the first flow meter 17 to the cooling body 10 from the second flow meter 18 to the cooling body 10. Are sequentially received from the pressure gauge 12 and a signal relating to the pressure P in the furnace.

  In subsequent step # 10, the control unit 22 sequentially calculates the flow rate difference ΔL (= L1−L2) between the inflow flow rate L1 and the outflow flow rate L2 from the received signals regarding the inflow flow rate L1 and the outflow flow rate L2. To do. At the same time, the pressure fluctuation ΔP per unit time is sequentially calculated from the signal related to the furnace pressure P.

  Next, in step # 15, the control unit 22 sequentially compares the calculated flow rate difference ΔL with a preset threshold value ΔLB. Information regarding the threshold ΔLB for the flow rate difference is stored in a memory mounted on the control unit 22. The threshold value ΔLB may be set in consideration of the detection accuracy of the first flow meter 17 and the second flow meter 18, and is preferably set to 30 cc / second or more from the detection accuracy of the current flow meter and the cooling water amount.

  At the same time, the calculated pressure fluctuation ΔP and a preset threshold value ΔPB are sequentially compared. Information regarding the threshold value ΔPB for the pressure fluctuation is also stored in the memory mounted in the control unit 22. The threshold value ΔPB is desirably set so that it is determined to be abnormal when there is a pressure fluctuation more than twice the maximum value of the pressure fluctuation in the furnace during normal operation without water leakage from the cooling body. .

  In step # 20, it is sequentially determined whether or not the flow rate difference ΔL exceeds the threshold value ΔLB. When water leakage occurs in the cooling body 10, the amount of water leakage appears as a flow rate difference ΔL. Here, the presence or absence of water leakage can be temporarily determined based on whether or not the flow rate difference ΔL exceeds the threshold value ΔLB. If the flow rate difference ΔL does not exceed the threshold value ΔLB, it is temporarily determined that there is no water leak and proceeds to step # 25. If it exceeds the flow rate difference ΔL, it is temporarily determined that there is water leak and the process proceeds to step # 30.

  In step # 25, it is sequentially determined whether or not the pressure fluctuation ΔP exceeds the threshold value ΔPB. When water leakage occurs in the cooling body 10, the water leakage is vaporized in the furnace body and the pressure in the furnace body rises, and this appears as a pressure fluctuation ΔP. The presence or absence can be temporarily determined. If the pressure fluctuation ΔP does not exceed the threshold value ΔPB, it is determined that there is no water leakage and the process returns to step # 5 to continue monitoring. If it exceeds the pressure fluctuation ΔP, it is temporarily determined that there is water leakage and the process proceeds to step # 35. .

If it is temporarily determined in step # 20 that there is water leakage, it is sequentially determined in step # 30 whether or not the pressure fluctuation ΔP has exceeded the threshold value ΔPB within a predetermined period starting from the time when the flow rate difference ΔL has exceeded the threshold value ΔLB. judge. That is, it is determined whether or not the pressure fluctuation ΔP exceeds the threshold value ΔPB almost simultaneously with the flow rate difference ΔL exceeding the threshold value ΔLB. The predetermined time period, from the viewpoint of reducing the influence of the flying noise on the flow meter output and one second or more, to set within 5 seconds from the viewpoint of reducing the damage caused by water leakage from the cold heat sink.

  When the flow rate difference ΔL and pressure fluctuation ΔP exceed the threshold values ΔLB and ΔPB almost simultaneously, two different phenomena due to water leakage appeared at the same timing in time. In this case, there is water leakage with high accuracy. It can be judged. If it is determined in step # 30 that there is water leakage, the process proceeds to step # 40 and appropriate safety measures are taken.

  On the other hand, when the flow rate difference ΔL and the pressure fluctuation ΔP do not substantially exceed the threshold values ΔLB and ΔPB almost simultaneously, two different phenomena due to water leakage appear at timings that are spaced apart from each other. Is not actually occurring, it can be assumed that the flow rate difference ΔL and the pressure fluctuation ΔP are erroneously detected, and it can be determined that there is no water leakage with high accuracy. If it is determined in step # 30 that there is no water leakage, the process returns to step # 5 and monitoring is continued.

  If it is temporarily determined in step # 25 that there is water leakage, in step # 35, the flow rate difference ΔL is the threshold value within a predetermined period, preferably within 1 second, starting from the time when the pressure fluctuation ΔP exceeds the threshold value ΔPB. It is sequentially determined whether or not ΔLB is exceeded. That is, it is determined whether or not the flow rate difference ΔL exceeds the threshold value ΔLB almost simultaneously with the pressure fluctuation ΔP exceeding the threshold value ΔPB.

  When the pressure fluctuation ΔP and the flow rate difference ΔL exceed the threshold values ΔPB and ΔLB almost simultaneously, it can be determined that there is water leakage with high accuracy as in step # 30. If it is determined in step # 35 that there is water leakage, the process proceeds to step # 40 and appropriate safety measures are taken.

  On the other hand, if the pressure fluctuation ΔP and the flow rate difference ΔL do not exceed the threshold values ΔPB and ΔLB almost simultaneously, it can be determined that there is no water leak with high accuracy, as in step # 30. If it is determined in step # 35 that there is no water leakage, the process returns to step # 5 and monitoring is continued.

  In step # 40, the following safety measures are taken.

  First, the control unit 22 sends a command to the first on-off valve 19, the second on-off valve 20, and the third on-off valve 21, and switches the first on-off valve 19 and the second on-off valve 20 from the open state to the closed state. Then, the third on-off valve 21 is switched from the closed state to the open state (see FIG. 3). If it does so, since the path | route of the water supply pipe 14 and the drainage pipe 15 will be interrupted | blocked, the water supply to the cooling body 10 is stopped forcibly. Together with this, the cooling water staying in the cooling body 10 is discharged to the outside through the branch pipe 16 whose path is opened. Here, the cooling water that has stopped flowing inside the cooling body 10 is heated under the influence of a high temperature in the furnace body, and is rapidly heated and vaporized, thereby causing volume expansion and high pressure. It will be ejected to the outside through the branch pipe 16 opened to the outside. Therefore, a steam explosion due to water leakage is prevented and safety is improved.

  Secondly, the fact that there is water leakage from the cooling body 10 is notified by uttering a warning sound or turning on a patrol light. Thereby, it can be recognized that water leakage has occurred in the cooling body 10.

  Third, energization of the heater 4 is stopped. At the same time, the rotation and elevation of the crucible 3 storing the melt 6 is stopped, and the rotation and elevation of the wire 7 suspending the single crystal 8 are stopped.

  In this single crystal growth apparatus, an example of processing based on detection values from the first flow meter 17, the second flow meter 18, and the pressure gauge 12 is shown in Table 1 below.

  Here, cases 1 to 3 are shown as an example. In any case, the threshold value ΔLB for the flow rate difference ΔL was set to 50 cc / second, and the threshold value ΔPB for the pressure fluctuation ΔP was set to 0.00013 MPa.

  In Case 1, the flow rate difference ΔL is 60 cc / second, which exceeds the threshold value ΔLB. The pressure fluctuation ΔP is 0.00005 MPa, which is within the threshold value ΔPB. In this case, it is determined that there is no water leakage regardless of the generation timing of the flow rate difference ΔL and the pressure fluctuation ΔP.

  In Case 2, the flow rate difference ΔL is 60 cc / second, which exceeds the threshold value ΔLB. The pressure fluctuation ΔP is 0.00020 MPa, which also exceeds the threshold value ΔPB. However, the generation timing of the flow rate difference ΔL and the pressure fluctuation ΔP is not simultaneous, but is longer than a predetermined period. In this case, it is determined that there is no water leakage.

  In Case 3, as in Case 2, the flow rate difference ΔL exceeds the threshold ΔLB at 60 cc / sec, and the pressure fluctuation ΔP exceeds 0.0Threshold MPa and the threshold ΔPB. However, the flow rate difference ΔL and the pressure fluctuation ΔP are generated at the same time. In this case, it is determined that there is water leakage.

  As described above, in the single crystal growth apparatus of the present embodiment, the leakage of the cooling water from the cooling body is determined based on the flow rate difference ΔL and the pressure fluctuation ΔP, and the flow rate difference ΔL and the pressure fluctuation ΔP are respectively determined. Since this is a separate phenomenon caused by water leakage, the determination of water leakage based on both is highly accurate. Therefore, leakage from the cooling body can be detected with high accuracy, and stable operation can be performed.

  In the single crystal growing apparatus of the present invention, water leakage from the cooling body can be detected with high accuracy and excellent in stable operability. Therefore, the present invention is extremely useful for a single crystal growth apparatus that uses a cooling body to increase the pulling speed.

It is a longitudinal section showing the composition of the single crystal growth device which is one embodiment of the present invention. It is a cross-sectional view of the single crystal growing apparatus of FIG. It is a systematic diagram of a water leak monitoring system. It is a flowchart which shows operation | movement of a water leak monitoring system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main chamber 2 Pull chamber 3 Crucible 4 Heater 5 Heat insulation cylinder 6 Melt 7 Wire 8 Single crystal 9 Heat shield 10 Cooling body 11 Vacuum exhaust pipe 12 Pressure gauge 13 Support arm 14 Water supply pipe 15 Drain pipe 16 Branch pipe 17 First flow rate Total 18 Second flow meter 19 First on-off valve 20 Second on-off valve 21 Third on-off valve 22 Control unit

Claims (2)

In a single crystal growth apparatus for growing a single crystal from a raw material melt in the furnace by the Czochralski method,
A cooling body that surrounds the single crystal grown from the raw material melt in the furnace and is cooled by cooling water flowing through the inside to cool the single crystal;
An outflow side flow meter for detecting the flow rate of the cooling water flowing out of the cooling body;
A pressure gauge for detecting the pressure in the furnace body;
The flow rate difference between them is calculated from the detection values of the inflow side flow meter and the outflow side flow meter, the pressure fluctuation per unit time is calculated from the detection value of the pressure gauge, and based on the flow rate difference and the pressure fluctuation. And a controller for determining the presence or absence of leakage of the cooling water ,
An apparatus for growing a single crystal characterized by determining that there is water leakage when the flow rate difference and the pressure fluctuation exceed a preset threshold value within a predetermined period of 1 second to 5 seconds . A water supply pipe connected to the cooling water inlet to the cooling body and provided with the inflow side flow meter in the path;
A drain pipe connected to an outlet of the cooling water from the cooling body and provided with the outflow side flow meter in the path;
A branch pipe branched from the drain pipe and opened to the outside;
A water supply pipe valve for opening and closing the path of the water supply pipe;
A drain valve for opening and closing the path of the drain pipe on the downstream side of the branch point to the branch pipe;
A branch pipe valve for opening and closing the path of the branch pipe,
The control unit, when it is determined that there is water leakage, switches the water supply pipe valve and the drain pipe valve from an open state to a closed state, and switches the branch pipe valve from a closed state to an open state. 1. The single crystal growth apparatus according to 1.

Images