JP4186763B2 - Process tube leak inspection method - Google Patents

Description

  The present invention relates to an inspection method for inspecting leakage of a process tube used in a core tube of a heat treatment furnace.

  Currently, in semiconductor wafer manufacturing processes and device manufacturing processes, heat treatment is performed under various conditions in order to oxidize and diffuse the wafer and improve the quality of the wafer.

  FIG. 2 is a schematic configuration diagram showing the structure of a horizontal heat treatment furnace which is one of typical heat treatment furnaces for heat-treating a semiconductor wafer or forming a CVD film. As shown in FIG. 2, a horizontal heat treatment furnace 11 that is generally used conventionally does not need a process tube 1 made of SiC or quartz for loading and processing a semiconductor wafer, and is not necessary in the case of SiC. However, in the case of quartz, an SiC soaking tube 12 into which the process tube 1 is inserted is disposed, and a heater 13 disposed around the SiC soaking tube 12 is provided. The process tube 1 has a cylindrical portion main body 14 that forms a heat treatment space, and a first gas introduction portion 2 that introduces a process gas into the process tube 1 at one end portion of the cylindrical portion main body 14, Moreover, the 2nd gas introducing | transducing part 3 which introduces the kind of process gas different from the 1st gas introducing | transducing part 2 as needed is formed, and is connected to the gas supply pipe | tube (not shown), respectively. The other end of the process tube 1 is formed with a loading port 4 for loading and unloading the semiconductor wafer. Further, on the loading port 4 side, a gas introduced into the process tube 1 is discharged. A discharge part 5 is formed.

  Then, using such a horizontal heat treatment furnace 11, for example, the atmospheric gas is continuously introduced into the process tube 1 from the first gas introduction unit 2 and the second gas introduction unit 3, and a desired temperature is obtained by the heater 13. The semiconductor wafer 16 held on the wafer boat 15 can be heat-treated by heating up to.

  When performing heat treatment on a semiconductor wafer using such a heat treatment furnace 11, it is necessary to replace the inside of the process tube 1 with an atmospheric gas in order to perform heat treatment stably, and the process tube used as a core tube of the heat treatment furnace It is necessary to use the one having high airtightness without causing leakage. In particular, in the heat treatment of a semiconductor wafer, hydrogen gas or the like may be used as an atmosphere gas. When heat treatment is performed using hydrogen gas or the like in this way, the atmosphere gas may leak from the process tube during the heat treatment. Unacceptable. Therefore, when performing heat treatment or the like, a leak inspection is performed in order to confirm whether or not there is a leak in the process tube before operation.

  In a conventional process tube leak inspection, for example, a method of visually inspecting a process tube from the outside is used. Normally, if there is a leak in the process tube, the portion has a rainbow color. Therefore, the presence or absence of the leak can be confirmed by visually observing the appearance of the used process tube. However, such a visual leak inspection can detect a relatively large leak, but it is very difficult to detect a small leak, so the reliability of the inspection result is low. In addition, a new process tube just delivered is difficult to observe because there is no rainbow color even if there is a leak.

  As a method for detecting small leaks existing in the process tube, for example, as shown in FIG. 3, the first gas introduction part 2 and the second gas introduction part 3 of the process tube 1 are plugged with a rubber stopper 19 or the like. A gas detector 18 and a vacuum pump 17 are connected to the discharge part 5 on the inlet 4 side. First, the inside of the process tube 1 is evacuated by the vacuum pump 17 to form a vacuum state, and then from the outside of the process tube 1. There is a method of performing a leak inspection by blowing a gas to a portion (leak inspection portion) where leakage is inspected with the nozzle 20 or the like and measuring the amount of leakage of the gas with a gas detector 18.

  Conversely, the second gas inlet 3 and the inlet 4 of the process tube 1 are plugged with a rubber plug 19 and the like, and the gas detector 18 and the vacuum pump 17 are connected to the first gas inlet 2. The inside of the process tube 1 is evacuated by the vacuum pump 17 to form a vacuum state, and then a gas is blown from the outside of the process tube 1 to a portion to be inspected for leakage by the nozzle 20 or the like. There is also a method of performing a leak inspection by measuring.

  By measuring the amount of leakage by blowing gas from outside the process tube 1 in which a vacuum state is formed in this way to measure the amount of leakage, the amount of leakage to be measured increases if there is a leakage in the inspection region. In addition, it is possible to detect the presence of relatively small leaks. The amount of leak is generally used as a measure of how much gas leaks in a vacuum vessel or the like, and indicates the flow rate of gas passing through the leak.

  Further, as another method, there is a method of performing a leak inspection on a process tube by applying a leak inspection apparatus for a vacuum processing chamber disclosed in Patent Document 1. For example, after evacuating the process tube with a vacuum pump as described above to form a vacuum state, the process tube leak is measured by measuring the differential pressure in the process tube before and after a certain time and comparing it with a reference value. Can be automatically inspected.

  However, in recent years, with the increase in the diameter of semiconductor wafers, the size of process tubes into which wafers are charged has also increased. Therefore, when inspecting for leaks in the process tube using the method described above, it takes a very long time to exhaust the inside of the process tube with a vacuum pump to form a vacuum state, and it takes a very long time. Therefore, there is a problem that a difference in the degree of vacuum is generated, and the leak check cannot be accurately performed at a portion where the degree of vacuum is insufficient.

  In recent years, as semiconductor devices have been miniaturized and highly integrated, demands for improving the quality of semiconductor wafers have increased, and it is possible to control the processing conditions such as heat treatment applied to the wafers with higher accuracy. is needed. For this reason, a heat treatment apparatus that performs heat treatment itself is required to have a higher quality, and the leak inspection of the process tube as described above can be performed with higher accuracy, and the presence or absence of a leak can be determined with high reliability. Development of inspection methods is desired.

JP-A-9-280995

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to perform a leak inspection of a process tube used in a heat treatment furnace or the like quickly and with high accuracy. An object of the present invention is to provide a method for inspecting a process tube with high reliability of the inspection result.

  In order to achieve the above object, according to the present invention, there is provided a method for inspecting a leak in a process tube, wherein a vacuum exhaust means is connected to each of at least two openings formed in the process tube and the vacuum is provided. A gas detector is further connected to one of the openings connected to the exhaust means, and the process tube is exhausted to a predetermined degree of vacuum by at least two vacuum exhaust means connected to the openings, and then the gas Close the opening other than the opening to which the detector is connected, and then blow the gas from the outside to the process tube and measure the leak amount of the process tube with the gas detector, thereby checking the leak of the process tube. A method for inspecting a leak in a process tube is provided (claim 1).

  By inspecting process tube leaks using such a method, there is no insufficient vacuum attainment in the process tube, and leaks are detected with very high accuracy, and the presence or absence of leaks is accurately determined. Therefore, a highly reliable leak test can be performed stably. Further, by using such a leak inspection method, the inspection time can be greatly reduced as compared with the conventional case, so that the leak inspection of the process tube can be performed quickly in a short time.

At this time, it is preferable that the inside of the process tube is evacuated to a degree of vacuum of 50 Pa or less by the evacuation means.
Thus, by evacuating the inside of the process tube to a vacuum degree of 50 Pa or less with a vacuum exhaust means, when measuring the amount of leak with a gas detector after blowing gas to the process tube, the measurement of the amount of leak was excellent. Since it can be performed with the measurement sensitivity, the leak inspection of the process tube can be performed with higher accuracy.

Moreover, it is preferable to use helium gas as the gas blown to the process tube, and to use a helium gas leak detector as the gas detector.
Thus, by using helium gas as the gas blown to the process tube and using the helium gas leak detector as the gas detector, a small leak existing in the process tube can be detected with very high accuracy. Further, since the helium gas is inert and easy to handle, the leak inspection can be easily performed.

Furthermore, it is preferable that the opening connecting the gas detector is an opening located at a position close to a leak inspection site of the process tube.
If the opening for connecting the gas detector is an opening at a position close to the leak inspection site of the process tube, the gas detector can further measure the amount of leak when the gas is blown to the leak inspection site. Since the measurement can be performed with excellent measurement sensitivity, it is possible to determine the presence or absence of a leak at the leak inspection site with extremely high accuracy.

In the process tube leak inspection method of the present invention, the process tube can be inspected for leaks having an inner diameter of 160 mm or more and / or a length of 1000 mm or more. A leak inspection can be performed on a tube made of SiC or quartz.
The process tube leak inspection method of the present invention is particularly suitable for performing a leak inspection on a large-sized process tube having an inner diameter of 160 mm or more and / or a length of 1000 mm or more, or a process tube made of SiC or quartz. If a leak test is performed on such a process tube by the leak test method of the present invention, the presence or absence of leak can be determined in a short time and with high reliability.

Furthermore, in the present invention, the leak inspection can be performed on a process tube used as a core tube of a heat treatment furnace (claim 7).
As described above, the present invention can perform a leak test on a process tube used as a core tube of a horizontal heat treatment furnace or a vertical heat treatment furnace, for example, before performing heat treatment on a semiconductor wafer. If the leak inspection of the process tube installed in the heat treatment furnace is performed by the leak inspection method of the invention, the presence or absence of leak in the process tube can be confirmed in a short time and with high reliability.

  As described above, according to the present invention, the leak of the process tube can be detected with very high accuracy, and the presence / absence of the leak can be accurately determined in a short time. It can be performed quickly and stably.

Hereinafter, although an embodiment is described about the present invention, the present invention is not limited to these.
The present inventor investigated the conventional leak inspection method as shown in FIG. 3 and found that the conventional leak inspection method takes a very long time to form a vacuum state by evacuating the process tube as described above. In addition to this problem, the process tube is evacuated by only one vacuum pump connected to one end of the process tube. In particular, in the case of a large-diameter process tube having an inner diameter of 160 mm or more, the internal volume is increased, so the process tube It has been found that a situation in which the degree of vacuum is insufficient occurs on the other end of the tube, and a stable vacuum state cannot be formed in the entire process tube such that the degree of vacuum varies depending on the position of the process tube. That is, in the conventional leak inspection, the inner diameter is not so large in the small-diameter process tube having an inner diameter of less than 160 mm, so there is not much problem. However, in the case of the large-diameter process tube, the process tube has an unstable vacuum. Because of this state, it became clear that even if there was a leak in the process tube at a position where the degree of vacuum was low, it could not be detected with high accuracy, and there was a lack of reliability in the inspection results.

  Therefore, the present inventor can solve the above-described problems, and can detect a leak in the process tube with high accuracy in a short time and promptly perform a highly reliable leak inspection. In order to develop a method that can do this, intensive research and examination were repeated. As a result, by connecting at least two evacuation means to the process tube and evacuating the process tube to a predetermined degree of vacuum, a stable vacuum state can be formed in the process tube in a short time. The present invention has been completed by finding that a leak inspection of a process tube can be performed with very high accuracy by spraying gas and measuring the amount of leak with a gas detector.

  Hereinafter, the process tube leak inspection method of the present invention will be described with reference to the drawings, but the present invention is not limited thereto. Here, FIG. 1 is a schematic explanatory view for explaining a leak inspection method for a process tube according to the present invention.

  The process tube leak inspection method of the present invention can be used for leak inspection of a process tube 1 used as a core tube of a horizontal heat treatment furnace 11, for example, as shown in FIG. The process tube 1 is formed with a first gas introduction portion 2 and a second gas introduction portion 3 for introducing a process gas to one tip portion, and a wafer is charged at the other end of the process tube 1. In addition, a charging port 4 for taking out is formed. Further, a discharge portion 5 for discharging the gas introduced into the process tube 1 is formed on the input port 4 side of the process tube 1.

  When leak inspection is performed on a process tube installed in a horizontal heat treatment furnace in this manner, first, an evacuation unit is connected to each of at least two openings formed in the process tube, and these vacuums are connected. A gas detector is further connected to one of the openings connected to the exhaust means.

  For example, as shown in FIG. 1, the first gas introduction part 2 formed at one end of the process tube and the discharge part 5 formed on the opposite side of the first gas introduction part 2 are each evacuated. A vacuum pump 6 is connected as a means, and a helium gas leak detector 7 capable of measuring the amount of He gas leak is connected to the first gas introduction unit 2 as a gas detector before the vacuum pump 6. Further, a valve 8 is provided between the discharge unit 5 and the vacuum pump 6 so that the valve 8 can be opened and closed. Further, for example, a rubber plug 9 is provided in the second gas introduction unit 3 to which no vacuum exhaust means is connected. Plug in.

  In the present invention, the connection position of the vacuum exhaust means and the gas detector is not limited to the above. For example, the vacuum pump can be connected to each of the second gas introduction unit 3 and the discharge unit 5, or can be connected to the first gas introduction unit 2 and the second gas introduction unit 3. In order to form a stable vacuum state by evacuating, it is preferable that a vacuum pump is connected to each side of the process tube 1 as shown in FIG. In the present invention, when the process tube has three openings such as the first gas introduction part, the second gas introduction part, and the discharge part, or more openings, three or more openings are formed. A vacuum pump can also be connected to the part.

  Further, the gas detector is preferably connected to an opening located at a position near the leak inspection site. Generally, process tube leaks often occur at connection points such as a connection portion between the cylindrical portion main body of the process tube and the first gas introduction portion, or a connection portion between the cylindrical portion main body and the second gas introduction portion. Therefore, it is important to perform a leak inspection on a portion where such a leak is likely to occur. Therefore, for example, in the case of mainly inspecting the leak in the vicinity of the connection portion between the cylindrical portion main body of the process tube and the first gas introduction portion, as shown in FIG. It is preferable to connect to the first gas inlet 2 that is close, so that, as will be described below, when measuring the amount of leak of He gas with the helium gas leak detector 7, the measurement of the amount of leak is further improved. Can be performed. On the other hand, when it is desired to inspect the leak on the inlet 4 side, it is preferable to connect the detector to the discharge part 5 side.

  After connecting the vacuum pump 6 and the helium gas leak detector 7 to the process tube 1 as described above, the inside of the process tube 1 is exhausted by the two vacuum pumps 6 connected to the first gas introduction part 2 and the discharge part 5, respectively. Then, the pressure is reduced to a predetermined degree of vacuum, for example, a degree of vacuum of 50 Pa or less. In this way, a stable vacuum state can be formed in the process tube in a short time by evacuating the process tube to a vacuum degree of 50 Pa or less, particularly about 30 to 20 Pa, with two vacuum pumps installed on both sides. .

  And after evacuating the inside of a process tube to a predetermined vacuum degree in this way and forming the stable vacuum state, opening parts other than the opening part to which the gas detector is connected are closed. That is, as shown in FIG. 1, when the helium gas leak detector 7 is connected to the first gas introduction unit 2, the valve 8 installed in the discharge unit 5 is closed.

  After that, using nozzle 10 from the outside of the process tube 1, for example, as shown in FIG. 1, He gas is blown onto an inspection site such as a connection portion between the cylindrical body of the process tube 1 and the first gas introduction unit 2. The He gas leak detector 7 measures the amount of He gas leak in the process tube 1. Thus, if He gas is blown from the outside of the process tube and the He gas leak amount is measured with the gas detector, the measured value (leak amount) of the gas detector increases if there is a leak in the process tube. When there is no leak, the measured value hardly changes, and therefore the presence or absence of a leak in the process tube can be easily determined in a short time of about several seconds. In this case, since He gas is used as the gas blown to the process tube, even a very small leak can be detected with high accuracy.

  At this time, since the inside of the process tube is depressurized to a vacuum degree of 50 Pa or less as described above, if there is a leak in the process tube, the change in the leak amount can be measured with excellent measurement sensitivity. Further, when the helium gas leak detector 7 is connected to the first gas introduction part 2 as shown in FIG. 1, for example, in the vicinity of the connection part between the cylindrical part body of the process tube 1 and the first gas introduction part 2. If there is a leak when He gas is blown, the change in the leak amount can be measured quickly and with very good sensitivity by the detector 7 connected near the gas introduction part 2, so that such a leak is likely to occur. It is possible to perform a leak inspection at a connection location with extremely high accuracy.

  By conducting a leak test on the process tube as described above, it is possible to detect leaks existing in the process tube with very high accuracy and accurately determine the presence or absence of leaks. It can be performed stably. In addition, if such a leak inspection method is used, the inspection time can be greatly reduced as compared with the conventional case, so that the leak inspection of the process tube can be performed quickly in a short time.

  In particular, the leak inspection method of the present invention leaks into a large process tube having an inner diameter of 160 mm or more and / or a length of 1000 mm or more and having a large degree of vacuum distribution, or a process tube made of SiC or quartz. It can be used very suitably when performing an inspection, and the leak inspection of such a process tube can be performed in a short time and with very high accuracy, and the presence or absence of a leak can be determined with high reliability.

  The process tube leak inspection method according to the present invention can be used not only for leak inspection of a process tube used as a core tube of a horizontal heat treatment furnace as shown in FIG. 1, but also, for example, a process tube used for a vertical heat treatment furnace. It can be used in the same manner for leak inspection, and can also be applied to quality inspection of a process tube before being installed in a heat treatment furnace.

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)
As an example, a leak test was performed on a SiC process tube having an inner diameter of 270 mm and a length of 2000 mm installed in a horizontal heat treatment furnace. As shown in FIG. 1, the process tube to be inspected this time has a first gas introduction portion 2 and a second gas introduction portion 3 formed at one end portion thereof, and also on the inlet 4 side of the process tube 1. The discharge part 5 is formed.

  In order to perform a leak test on such a process tube 1, as shown in FIG. 1, a helium gas leak detector 7 and a vacuum pump 6 are connected to the first gas introduction unit 2, while a valve 8 is connected to the discharge unit 5. The vacuum pump 6 was connected via The second gas introduction part 3 was plugged with a rubber plug 9.

Next, the process tube 1 was evacuated for 30 minutes with two vacuum pumps 6 connected to the first gas introduction part 2 and the discharge part 5, respectively, and the pressure was reduced to 30 Pa. Subsequently, after the valve 8 is closed, He gas is blown onto the connecting portion between the cylindrical portion main body of the process tube 1 and the first gas introducing portion 2 using the nozzle 10 and the He gas leak amount is measured by the helium gas leak detector 7. did. As a result, the measured value of the helium gas leak detector 7 increased from 1.2 × 10 ⁻⁷ Pa · m ³ / S to 7.0 × 10 ⁻⁵ Pa · m ³ / S. It was confirmed that there was a leak at the site where this He gas was sprayed.

(Comparative example)
In order to perform a leak test on the same process tube 1 as in the above embodiment by a conventional method, the first gas inlet 2 and the second gas inlet 3 are plugged with rubber stoppers 19 and discharged as shown in FIG. The gas detector 18 and the vacuum pump 17 were connected to the unit 5. Next, after the process tube 1 is evacuated for 30 minutes using only the vacuum pump 17 connected to the discharge unit 5, He gas is blown to the same part as in the above embodiment using the nozzle 20, and the leak amount is reduced by the gas detector 18. It was measured. As a result, the measured value of the gas detector 18 remained almost unchanged at a value of 1.2 × 10 ⁻⁷ Pa · m ³ / S, and therefore no leak could be confirmed.

  The present invention is not limited to the above embodiment. The above embodiment is merely an example, and the present invention has the same configuration as that of 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.

  For example, in the above description, the case where the leak inspection is mainly performed in the connection portion between the cylindrical portion main body of the process tube and the gas introduction portion is described as an example, but the present invention is not limited to this, By changing the portion to which the gas is blown when measuring the leak amount, the leak inspection can be performed at various positions of the process tube. Furthermore, the present invention can be similarly applied even if the process tube has various shapes.

It is a schematic explanatory drawing explaining the leak test method of the process tube of this invention. It is a schematic block diagram which shows the structure of a horizontal type heat processing furnace. It is a schematic explanatory drawing explaining the leak inspection method of the conventional process tube.

Explanation of symbols

1 ... process tube, 2 ... first gas introduction part,
3 ... second gas introduction part, 4 ... inlet, 5 ... discharge part,
6 ... Vacuum pump (evacuation means),
7 ... Helium gas leak detector (gas detector), 8 ... Valve,
9 ... rubber plug, 10 ... nozzle, 11 ... horizontal heat treatment furnace,
12 ... SiC soaking tube, 13 ... Heater, 14 ... Cylindrical body,
15 ... Wafer boat, 16 ... Semiconductor wafer,
17 ... Vacuum pump, 18 ... Gas detector, 19 ... Rubber stopper,
20 ... Nozzle.

Claims (7)

  A method for inspecting a leak in a process tube, wherein a vacuum exhaust means is connected to each of at least two openings formed in the process tube, and a gas detection is further detected in one of the openings connected to the vacuum exhaust means. And after evacuating the process tube to a predetermined degree of vacuum with at least two vacuum evacuation means connected to the opening, open an opening other than the opening to which the gas detector is connected. A process tube leak inspection method comprising: closing and then injecting gas from outside into the process tube and measuring a leak amount of the process tube with the gas detector to perform a leak inspection of the process tube.   2. The process tube leak inspection method according to claim 1, wherein the vacuum exhaust means exhausts the inside of the process tube to a vacuum degree of 50 Pa or less.   3. The process tube leak inspection method according to claim 1, wherein a gas to be blown onto the process tube is helium gas, and a helium gas leak detector is used as the gas detector.   4. The process tube according to claim 1, wherein the opening connecting the gas detector is an opening located at a position close to a leak inspection site of the process tube. 5. Leak inspection method.   The leak inspection method for a process tube according to any one of claims 1 to 4, wherein a leak inspection is performed on the process tube having an inner diameter of 160 mm or more and / or a length of 1000 mm or more. .   6. The process tube leak inspection method according to claim 1, wherein a leak inspection is performed on the process tube made of SiC or quartz.   The process tube leak inspection method according to any one of claims 1 to 6, wherein the leak inspection is performed on a process tube used as a core tube of a heat treatment furnace.

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