JP2009287573A - Turbo molecular pump and method for predicting breakdown thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To predict time of breakdown (breakdown of a moving blade) of a turbo molecular pump. <P>SOLUTION: The turbo molecular pump P, which is provided with a stationary blade 3 in a rotor chamber 2, and a motor 11 wherein a rotor shaft 4a mounted with the moving blades 5 is rotatably supported in the rotor chamber 2 through radial magnetic bearings 7a, 7b and a thrust magnetic bearing 8 to rotate the rotor shaft 4a at a high speed in the pump, comprises a displacement sensor 7b' for detecting vibration of the rotor shaft 4a, a control part for recognizing whether the vibration is pulse variation or not, a second control part for authorizing the pulse variation recognized by the control part as shaft displacement which causes the breakdown of the turbo molecular pump, and an integrating means to count the number of the shaft displacement causing the breakdown which is authorized by the second control part. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a turbo molecular pump used in a semiconductor manufacturing process and a failure prediction method thereof.

The semiconductor process is realized by various processes including optical processing and chemical processing. Typical examples of the optical processing include exposure processing for baking a circuit pattern on the wafer surface, and chemical processing includes, for example, surface processing such as forming a thin film on the wafer surface, etching processing, cleaning processing, and the like. It is done. In order to realize these processes, an exposure apparatus is used for optical processing, and various chemicals and various devices for safely handling these are used for chemical processing. In these various processes or various devices and equipment, as the demand for further higher integration of semiconductors and the like is increasing, each is required to have a high technical level and further development is required. In order to achieve this, intensive research and development are going on at various places concerned.

Among them, a specific technique is an etching technique for forming a groove on the surface of a substrate when paying attention to a chemical treatment process. This etching is a technique in which a source gas is supplied to a substrate such as a wafer and plasma is generated to form a desired groove on the substrate through a chemical reaction on the substrate. This technology is indispensable for realizing high integration of semiconductors such as thinning of gates and reduction of inter-wiring capacitance.

By the way, in order to realize the above-described etching, an apparatus for realizing a stable supply of gas, and an environmental maintenance that keeps the area around the substrate surface clear so as to effectively advance the chemical reaction on the substrate surface. Equipment is needed. In general, many gases used in etching are extremely toxic, and sufficient care must be taken in handling them. Therefore, it is indispensable to consider this point with respect to gas supply equipment and equipment for recovering it. In addition, as a method of “keeping the area around the substrate surface clear”, specifically, a means for revealing a vacuum atmosphere is generally taken, and therefore a vacuum exhaust system is prepared to realize this. It becomes.

As the evacuation system, a system constituted by a plurality of pumps such as a rotary pump, a diffusion pump, and a turbo molecular pump is generally used so as to enable multi-stage evacuation from atmospheric pressure. Among these, in the vacuum exhaust system including the turbo molecular pump, an ultra-high vacuum whose vacuum degree reaches about 10 ⁻¹⁰ Torr is realized. As is well known, a turbo molecular pump has a configuration in which gas molecules are struck and exhausted by a rotor rotating at about several tens of thousands rpm per minute.

Conventionally, there has been an attempt to store an event immediately before an abnormality of a turbo molecular pump so that the stored result can contribute to an investigation of the cause of the abnormality (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2000-74063 (FIG. 3)

However, in the case of the above-mentioned Patent Document 1, since a failure that would occur in the future (for example, damage to a moving blade) could not be predicted, in the worst case, the moving blade was damaged, and the turbo molecular pump was In addition to stopping, there is a risk of stopping the entire apparatus.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a turbo molecular pump capable of predicting a failure and a failure prediction method thereof.

The present invention employs the following means in order to solve the above problems.
The turbo molecular pump according to claim 1, wherein a stator blade is provided in a rotor chamber, a rotor shaft to which a moving blade is attached is rotatably supported in the rotor chamber via a magnetic bearing, and the rotor shaft is rotated at a high speed. In a turbo molecular pump equipped with a motor in a pump, a displacement sensor for detecting vibration of the rotor shaft, the vibration value of the rotor shaft, the rotation speed of the motor, and the current value of the motor are compared with predetermined conditions. When the condition is satisfied, the control unit recognizes the vibration value as a pulse-like fluctuation, and transmits a signal indicating that the pulse-like fluctuation has occurred after a predetermined time has passed to the second control unit. When the current value of the motor when the transmission means and the transmission means transmit a signal is equal to or less than a predetermined value, the pulse-like fluctuation recognized by the control unit And includes a second control unit to certify that the axial displacement causes the failure of the flop, and integrating means for said second control unit counts the number of axial displacement causes the failure certified, the It is characterized by having.

According to such a turbo molecular pump, the vibration of the rotor shaft is detected by the displacement sensor, the control unit recognizes whether the vibration is pulse-like , and the pulse-like fluctuation recognized by the control unit is detected. If the second control unit recognizes whether or not the shaft displacement is a cause of failure of the turbo molecular pump , as a result, if the shaft displacement causes the failure of the turbo molecular pump, As a signal to the integrating means, and the number of times is counted by the integrating means.
That is, the number of shaft displacements that cause a failure that has occurred in the rotor shaft is stored in the integrating means.

The turbo molecular pump according to claim 2, wherein an alarm is issued when the number of integrations counted by the integration unit exceeds a predetermined number, or when the number of times counted by the integration unit exceeds a predetermined number within a predetermined time. And alarm means for emitting

According to such a turbo-molecular pump, when the number of integrations counted by the integration unit exceeds a predetermined number, or when the number of times counted by the integration unit exceeds a predetermined number within a predetermined time, an alarm unit alarms. Can be emitted.

The failure prediction method for a turbo molecular pump according to claim 3, wherein a rotor blade is provided in a rotor chamber, and a rotor shaft to which a rotor blade is attached is rotatably supported in the rotor chamber via a magnetic bearing. In a turbo molecular pump having a motor that rotates the motor at high speed, the vibration value of the rotor shaft, the rotation speed of the motor, and the current value of the electric motor are compared with predetermined conditions, and the conditions are satisfied. In addition, after the first stage for recognizing the vibration value as a pulse-like fluctuation, and after the first stage, the current value of the motor is compared with a predetermined value, and the first value is less than or equal to the predetermined value. A second stage that recognizes that the pulse-like fluctuation recognized in the stage is a shaft displacement that causes a failure of the turbo molecular pump, and a cumulative number of shaft displacements that cause the fault that is recognized in the second stage Ah There is characterized in that it comprises a third step of counting the number of occurrences, the

According to such a failure prediction method of the turbo molecular pump, to detect the vibration of the rotor shaft, it recognizes whether the vibration is of a pulsed, further recognized pulsed variation of the turbo molecular pump It is determined whether or not the shaft displacement is a cause of failure . As a result, if the shaft displacement is a cause of failure of the turbo molecular pump , the number of times of accumulation or occurrence is counted.
That is, the number of axial displacements that cause a failure in the rotor shaft is counted.

5. The turbo molecular pump failure prediction method according to claim 4, wherein the cumulative number counted in the third stage exceeds a predetermined number, or the occurrence number counted in the third stage is within a predetermined time. And a step of issuing an alarm when the predetermined number of times is exceeded.

According to such a failure prediction method for a turbo molecular pump, an alarm is issued when the counted number exceeds a predetermined number or when the counted number exceeds a predetermined number within a predetermined time. .

The turbo molecular pump and its failure prediction method according to the present invention have the following effects.
According to the turbo molecular pump according to claim 1 or the turbo molecular pump failure prediction method according to claim 3, the number of axial displacements that cause a failure in the rotor shaft is counted, and the number can be easily determined. Since it is possible to know, it is possible to predict the failure time of the turbo molecular pump only by looking at the number of times, and it is possible to inspect or replace parts before the failure, thereby avoiding the stoppage of the device due to the failure.
In addition, the most efficient maintenance is possible according to the time, and the turbo molecular pump and the entire apparatus can always be maintained in a good state.
Furthermore, since the time of maintenance becomes clear, it is sufficient to prepare necessary spare parts according to the time, and planned preparation is possible.

According to the turbo molecular pump according to claim 2 or the turbo molecular pump failure prediction method according to claim 4, when the counted number exceeds a predetermined number, or the counted number reaches a predetermined number within a predetermined time. If it exceeds the limit, an alarm is issued, so that the failure time can be ascertained reliably, human error can be eliminated, and reliable maintenance and inspection work can be performed.

It is a vertical side view of the turbo-molecular pump in one embodiment of this invention. It is a graph for demonstrating the pulse-like fluctuation | variation which arises in a rotor shaft. It is a schematic block diagram for demonstrating the logic by this invention. It is the graph which showed the frequency | count of the pulse-like axial displacement which occurred from the operation start of the turbo molecular pump until a rotor blade destroyed.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
A turbo molecular pump, which is a type of rotary vacuum pump, is widely used for vacuuming semiconductor manufacturing equipment. FIG. 1 shows a schematic structure of a turbo molecular pump.

The turbo molecular pump P has a configuration in which various components are provided inside the casing 1. In the casing 1, an intake port 1 c is formed in the upper half 1 a and an exhaust port 1 d is formed in the lower half 1 b. Has been.

A rotor 4 is disposed in the rotor chamber 2 inside the casing 1. The rotor 4 has a configuration including a rotor shaft 4a erected vertically and moving blades 5 arranged radially around the rotor shaft 4a. A stationary blade 3 is fixed to the casing upper half 1a. Since the rotor 4 is a member that rotates at a high speed, it is generally preferable to select an aluminum alloy or the like that is lightweight and has high stress strength as the material.

A thrust magnetic disk 6 is provided at the lower end of the rotor shaft 4a. Thrust magnetic bearings 8 are provided on the upper and lower surfaces of the thrust magnetic disk 6 so as to oppose them. Further, radial magnetic bearings 7a and 7b are respectively provided above and below the facing surface between the rotor shaft 4a and the casing lower half 1b. Further, a ball bearing 9 provided as a radial upper protective bearing is provided at the upper end portion of the rotor shaft 4a, and a ball bearing 10 provided as a radial and thrust lower protective bearing is provided at the lower end neck portion. A rotor driving motor 11 is provided in the casing lower half 1b.

On the other hand, the radial magnetic bearings 7a, 7b and the thrust magnetic bearing 8 are provided with position sensors (displacement sensors) 7a ', 7b', 8 ', respectively, and the current value flowing through the electromagnets of these magnetic bearings 7a, 7b, 8 Are controlled by feedback from signals from the position sensors 7a ′, 7b ′, 8 ′ to adjust the generated electromagnetic force and support the rotor 4 in a non-contact manner to operate as a bearing.

During vacuum evacuation, if the motor 11 is driven to rotate the rotor 4, compression is performed between the moving blade 5 and the stationary blade 3 by the rotation of the rotor 4, and then flows in the direction of the exhaust port 1 d. And evacuated.

Now, the inventor repeatedly performs the test operation of the turbo molecular pump P as described above, and the rotor generated when the reaction product adheres (particularly, when the process ends and the motor load decreases). It is newly found that there is a correlation between the number of occurrences of pulse-like fluctuations in the shaft 4a and the failure time of the turbo molecular pump P (in the actual test, when the rotor blades of the turbo molecular pump P are destroyed). I found it.
In other words, the failure time of the turbo molecular pump P can be predicted by counting (accumulating) such pulse-like fluctuations in the rotor shaft 4a with a counter (integrator).
The reaction product referred to here includes, for example, aluminum chloride (AlCl ₃ ), ammonium chloride (NH ₄ Cl), tungsten pentachloride (WCl ₅ ), indium iodide (InI ₃ ), and the like.

The pulse-like fluctuation of the rotor shaft 4a is, for example, as shown in FIG. FIG. 2 shows the vibration value of the rotor shaft 4a at a certain time (between 18:23:00 and 18:25:00 in the figure) when a test operation is performed using a turbo molecular pump P of 1400 liter class. [mu] m], a graph showing changes in motor current value (mA) and rotation speed (rps). In the test operation shown in FIG. 2, it can be seen that the rotor shaft 4a is operated at about 519 revolutions per second (31,140 revolutions per minute). It can also be seen that the motor current decreased from about 1430 mA (1.43 A) to about 660 mA over time because the process was completed at 18:23:30 and the motor load was reduced.

At 18:23:55, the aforementioned pulse-like fluctuation of the rotor shaft 4a (in this case, a large amplitude of about once per second, so-called 1-second pulse) can be seen. At this time, it can be seen that the vibration value that was stable at about 2.5 μm suddenly increased to about 11 μm, and the motor current value that was about 660 mA rapidly increased to about 900 mA.
Here, such a pulse-like fluctuation of the vibration value also occurs, for example, when a valve (valve) provided adjacent to the turbo molecular pump P is closed. However, when the valve provided adjacent to the turbo molecular pump P is closed, the pulse-like fluctuation of the motor current value is not detected, so that the valve provided adjacent to the fluctuation or the cause of failure is closed. It is possible to determine whether the fluctuation is due to disturbance such as by looking at the change in the current value.
In FIG. 2, after 18:24:10, it seems that the vibration value of the rotor shaft 4a is settled at about 4.5 μm, but gradually decreases with time, and the original vibration value (about Finally return to 2.5 μm). The vibration value can be obtained by measuring the voltage of a position sensor (displacement sensor) 7b ′ provided below the radial magnetic bearing 7b. For example, when the voltage value is 0.089 V, the vibration value is 9 μm.

Next, the logic according to the present invention for counting such pulse-like fluctuations will be described with reference to FIG.
This logic is composed mainly of a control unit (determination unit) 21, a second control unit 22, a counter (integration unit) C, an alarm unit (alarm unit) A, and a display unit D. It is.
The control unit 21 is constantly sent with vibration value, motor current, and motor rotation number data. In the control unit 21, the motor current value is 0.7A or more, the motor current value is 2.0A or less, and the motor rotation number is 519r. p. s. When all of the above conditions are met, a steady process state is defined, and a vibration value of 9 μm or more in that state is recognized (determined) as a pulse-like variation.
Then, after 30 seconds, a signal indicating that there has been a pulse-like variation is sent from the control unit 21 to the second control unit 22, and at that time (a signal indicating that there has been a pulse-like variation from the control unit 21) Data of the motor current (when it is sent) is sent to the second controller. If the motor current value at this time is 2.0 A or less, a signal is sent to the counter C and counted, assuming that the shaft displacement (shaft vibration) that causes the failure has occurred once. The count can store the cumulative total from the start of operation until now, and can also store the number of occurrences every day.
The reason that the motor current value is 2.0 A or less is that the motor current value becomes higher than 2.0 A during the vacuum chamber cleaning process. That is, it is to prevent counting of pulse-like fluctuations of the rotor shaft 4a that occur during the cleaning process.

FIG. 4 shows how many times the count in the counter C has been performed on what day from the start of operation, how much the count has accumulated, and how much the motor current value at that time is. is there. In FIG. 4, ● represents the number of times counted by the counter C on the day (vibration frequency), ■ represents the total number of times counted by the counter C until that day (vibration cumulative number), and ◆ represents the motor current value on that day. ing.
When the 10th count (the 77th count in total) is performed on the last day of the data, that is, on the 380th day after starting the operation, the rotor blades of the turbo molecular pump P are damaged and the turbo The molecular pump P has stopped.

As shown in FIG. 4, the rotor blades of the turbo molecular pump P were destroyed after a while (after 80 days) from the day (300th day) when the total number of times counted by the counter C began to increase rapidly. Yes. Further, after a while (50 days later) from the day (day 330) when the number of times counted by the counter C reaches 10 times a day, the moving blades of the turbo molecular pump P have been destroyed.

Therefore, the turbo is soon (not too far away) from the day when the total number of times counted by the counter C starts to increase suddenly or the day when the number counted by the counter C reaches 10 times a day. It can be predicted that the moving blades of the molecular pump P will be destroyed.
Although it is not impossible to predict the failure of the turbo molecular pump P by looking at the increase in the current value, it is possible to more reliably detect the failure by looking at the vibration frequency or the cumulative number of vibrations that increase more rapidly than the current value. Can be predicted.

In the case of the turbo molecular pump P of 1400 liter class used in the test operation, it was found that there was a tendency as described above. For example, the total number of times counted by the counter C started to increase rapidly. After 60 days from the day, or after 30 days from the day when the number counted by the counter C reaches 10 times a day, the operation of the turbo molecular pump P is stopped and maintenance work such as parts replacement is performed. It is possible to prevent the rotor blades of the turbo molecular pump P from being destroyed.

In this way, since the day when the rotor blade of the turbo molecular pump P will be destroyed can be accurately predicted, it is possible to inspect before the failure or replace the parts, and to avoid stopping the device due to the failure. Yes (preventive maintenance).
In addition, the most efficient maintenance is possible according to the time, and the turbo molecular pump P and the entire apparatus can always be maintained in a good state.
Furthermore, since the time of maintenance becomes clear, it is sufficient to prepare necessary spare parts according to the time, and planned preparation is possible.

Further, as shown in FIG. 3, it is more preferable that the result accumulated in the counter C (in other words, the graph as shown in FIG. 4) is displayed on the display device D to urge the user to call attention. It is.
By configuring in this way, it is not necessary for the user to access the counter C and perform confirmation work one by one, and the monitoring work can be simplified.

Further, a signal indicating that the total number of times counted by the counter C has begun to increase suddenly or that the number counted by the counter C has reached 10 times a day is sent to the alarm device A, It is more preferable to inform the user by sound or voice.
By configuring in this way, even if the user overlooks or mistakes the display displayed on the display device D, it is possible to reliably grasp the date when the moving blade of the turbo molecular pump P will be destroyed. It is possible to eliminate human error and to perform reliable maintenance inspection work.

The vibration values, motor currents, and motor rotation speeds described above are not limited to those described above, but may vary depending on the size of the turbo molecular pump P, usage conditions, and the like.

Further, the turbo molecular pump P is not limited to the one shown in FIG. 1, and may have any form as long as it has the same configuration.

Furthermore, in the above-described embodiment, the axial displacement of the rotor shaft 4a is detected by the position sensor (displacement sensor) 7b 'provided below the radial magnetic bearing 7b. However, the present invention is limited to this. Instead, it can also be detected by a position sensor (displacement sensor) 7 a ′ provided above the radial magnetic bearing 7 a and a position sensor (displacement sensor) 8 a provided below the thrust magnetic bearing 8.

2 Rotor chamber 3 Stator blade 4a Rotor shaft 5 Rotor blade 7a Radial magnetic bearing 7b Radial magnetic bearing 7b 'Position sensor (displacement sensor)
8 Thrust magnetic bearing 11 Motor 21 Control unit (judgment means)
A Alarm (alarm means)
C counter (accumulation means)

Claims (4)

In a turbo molecular pump provided with a stationary blade in a rotor chamber, a rotor shaft to which a rotor blade is attached is rotatably supported in the rotor chamber via a magnetic bearing, and a motor that rotates the rotor shaft at a high speed is provided in the pump. ,
A displacement sensor for detecting vibration of the rotor shaft;
A control unit that compares the vibration value of the rotor shaft, the rotation speed of the motor, and the current value of the motor with predetermined conditions, and recognizes the vibration value as a pulse-like variation when the conditions are satisfied;
A transmission means for transmitting a signal indicating that the pulse-like fluctuation has occurred to the second control unit after a predetermined time has elapsed;
When the current value of the motor when the transmission means transmits a signal is a predetermined value or less, the pulse-like fluctuation recognized by the control unit is an axial displacement that causes a failure of the turbo molecular pump. A second controller to authorize;
A turbo molecular pump comprising: an accumulating unit that counts the number of axial displacements that cause a failure that is recognized by the second control unit . Alarm means for issuing an alarm when the integration count counted by the integration means exceeds a predetermined count, or when the count counted by the integration means exceeds a predetermined count within a predetermined time. The turbo-molecular pump according to claim 1, wherein In a turbo molecular pump provided with a stationary blade in a rotor chamber, a rotor shaft to which a rotor blade is attached is rotatably supported in the rotor chamber via a magnetic bearing, and a motor that rotates the rotor shaft at a high speed is provided in the pump. ,
The vibration value of the rotor shaft, the rotational speed of the motor, and the current value of the electric motor are compared with a predetermined condition, and when the condition is satisfied, the vibration value is recognized as a pulse-like variation. Stages,
After the first stage, the current value of the motor is compared with a predetermined value, and when it is equal to or less than the predetermined value, the pulse-like fluctuation recognized in the first stage causes a failure of the turbo molecular pump. A second stage of identifying the axial displacement ;
A turbo molecular pump failure prediction method comprising: a third step of counting the number of times of axial displacement integration or occurrence that is a cause of the failure identified in the second step . A step for issuing an alarm when the case where the third cumulative number of times more counts the stage of exceeds a predetermined number of times, or the third counted number of occurrences by stage exceeds a predetermined number of times within a predetermined time, The turbo molecular pump failure prediction method according to claim 3, further comprising:

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