This application is a U.S. national phase application under 35 U.S.C. § 371 of international application number PCT/JP2019/021925 filed on Jun. 3, 2019, which claims the benefit of priority to JP application number 2018-114954 filed Jun. 15, 2018. The entire contents of each of international application number PCT/JP2019/021925 and JP application number 2018-114954 are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a vacuum pump and a temperature control device, and particular to a vacuum pump and a temperature control device capable of preventing, with a simple configuration, overheating and overcooling of a pump that are caused due to abnormality in a temperature sensor used to control a heater or a water-cooling solenoid valve that is provided to prevent the deposition of products.

BACKGROUND

With the recent development of electronics, the demand for semiconductors such as memories and integrated circuits has been increasing rapidly.

These semiconductors are manufactured by providing electrical properties by doping extremely pure semiconductor substrates with impurities or by forming a fine circuit on a semiconductor substrate by means of etching.

These tasks need to be performed in a chamber in a high vacuum state in order to avoid the impact of dust and the like in the air. Typically a vacuum pump is used to exhaust the chamber, and particularly a turbomolecular pump, which is a type of a vacuum pump, is often used less from the perspective of gas and easy maintenance.

Furthermore, the process of manufacturing a semiconductor includes many steps of causing various process gases to act on a semiconductor substrate, wherein a turbomolecular pump is used not only to make the chamber vacuum, but also to exhaust these process gases from the chamber.

Incidentally, the process gases may be introduced into the chamber at a high temperature in order to increase the reactivity. These process gases may become solid once these process gases are cooled to a certain temperature at the time of exhaustion, and thereby deposit products in an exhaust system. Subsequently, these types of process gases may become solid upon reaching a low temperature within the turbomolecular pump, and consequently adhere to and accumulate on the inside of the turbomolecular pump.

When the deposits of the process gases accumulate inside the turbomolecular pump, these accumulated products narrow a pump flow path, reducing the performance of the turbomolecular pump.

In order to solve this problem, conventionally, a heater or an annular water cooling pipe is wrapped around an outer circumference of a base portion or the like of the turbomolecular pump, and, for example, a temperature sensor is embedded in the base portion or the like, wherein the base portion is heated by the heater or cooled by the water cooling pipe to keep the temperature of the base portion in a constant range of high temperatures on the basis of a signal from the temperature sensor (temperature management system (hereinafter referred to as TMS)) (see Japanese Patent Application Publication No. 2002-257079 and Japanese Patent No. 5782378).

Because the higher the control temperature by the TMS, the more difficult it is for the products to accumulate, it is preferred that the temperature of the base portion be as high as possible.

On the other hand, when the temperature of the base portion is high, an electronic circuit provided in the main body of the turbomolecular pump exceeds a limit temperature in a case where, for example, due to changing to the high temperature of the electronic circuit with a case the exhaust load fluctuates or the ambient temperature becomes high, possibly destroying a storage means of a semiconductor memory. In such a case, the semiconductor memory is destroyed, resulting in loss of maintenance information data such as pump startup time and error history.

Loss of the maintenance information data makes it impossible to determine when to perform maintenance and

inspection or when to replace the turbomolecular pump. Consequently, a major problem occurs in the operation of the turbomolecular pump. For this reason, the base portion is cooled by the water cooling pipe when the temperature of the base portion exceeds a predetermined temperature.

An example of the TMS control is illustrated in a flowchart inFIG. 7and a timing chart inFIG. 8. In the timing chart inFIG. 8, the horizontal axis represents the times at which the heater is controlled and the vertical axis represents temperature values measured by the temperature sensor. The ON state and the OFF state of the heater are also shown on the vertical axis. Note that opening and closing of the solenoid valve for controlling the flow of water into the water cooling pipe take place in the form of control by a temperature sensor, independent of the control of the heater, the temperature sensor being provided separately. However, since this control method of the solenoid valve is the same as the control of the heater, a flowchart and a timing chart for the control of the solenoid valve are omitted herein.

In this example, the temperature of the base portion of the turbo molecular pump is measured by the temperature sensor, and a heating command is sent to the heater or the solenoid valve is opened and closed to control the flow of water into the water cooling pipe, so that the measured temperature becomes equal to or lower than an allowable temperature of the base portion that is set in advance.

In other words, inFIGS. 7 and 8, after the operation starts, the control device turns the heater ON during an initial stage up to time t2and continues to heat the base portion. At this moment, the processing is performed by a control CPU on the basis of the flowchart illustrated inFIG. 7. Specifically, the TMS control is activated according to this flowchart, every certain sampling cycle Δt. First, up to time t1, the control of the heater begins in step 1 (abbreviated as S1in the diagram, and the same applies hereinafter), and since the temperature measured by the temperature sensor is determined to be lower than a lower limit in step 2, the heater is turned ON in step 3, and then the control ends in step 4. This operation is repeated for the control performed every sampling cycle Δt up to time t1.

During the sampling cycle Δt from time t1to time t2, the control of the heater begins in step 1, and in step 2, since the temperature measured by the temperature sensor is determined to be equal to or higher than the lower limit, the processing proceeds to step 5. However, in step 5, since the measured temperature is lower than an upper limit, the processing proceeds to step 4 where the control is ended. That is, until time t2where the upper limit is reached, the heater remains ON and continues to be heated.

In step 5, it is determined that the measured temperature exceeds the upper limit for the first time at time t2. Thus, the processing proceeds to step 6 where the heater is turned OFF.

In view of the heat capacity even after the heater is turned OFF at the upper limit, the temperature of the base portion does not drop suddenly, resulting in drawing an overshoot curve. On the other hand, around the time when the measured temperature exceeds the upper limit, the control of the solenoid valve is performed separately, in which the solenoid valve is opened and water is supplied from the water cooling pipe.

After the overshoot, during the sampling cycle Δt up to time t3, it is determined in step 2 that the measured temperature is not lower than the lower limit and in step 5 that the measured temperature is not higher than the upper limit; the processing proceeds to step 4. Thus, the heater remains OFF.

Then, when the temperature of the base portion becomes lower than the lower limit at time t3, it is determined in step 2 that the temperature of the base portion is lower than the lower limit, and the processing proceeds to step 3 where the heater is turned ON again. Around the time when the temperature of the base portion becomes lower than the lower limit, the solenoid valve is closed by the solenoid valve control that is carried out separately.

SUMMARY

Incidentally, in some cases a thermistor is used as the temperature sensor in order to perform the TMS control. In such a case, when a cable breaks, the resistance value of the thermistor becomes infinite. At that time, a temperature of, for example, −150 degrees is detected as the temperature value obtained by converting the resistance value into a voltage. On the other hand, when the cable shorts out, the resistance value becomes zero, and an abnormal temperature of, for example, 600 degrees is detected as the voltage-converted temperature value.

Furthermore, in a case where the temperature sensor is not placed correctly due to, for example, a gap formed between the temperature sensor and a wall portion of the pump or a short circuit caused via the aluminum of the wall portion, the measured temperature value may not be a specific value as described above.

Additionally, in a case where the temperature sensor uses serial communication, the temperature may be locked to the last measured temperature when the temperature sensor system has malfunctioned.

If the TMS control continues without being able to detect such circumstances, overheating, overcooling or the like of the pump occurs, resulting in impairment of the function of the pump.

The present disclosure has been contrived in view of these problems of the prior art, and an object thereof is to provide a vacuum pump and a temperature control device that are capable of preventing, with a simple configuration, overheating and overcooling of a pump that are caused due to abnormality in a temperature sensor used to control a heater or a water-cooling solenoid valve that is provided to prevent the deposition of products.

Thus, the present disclosure is a disclosure of a vacuum pump, including: a temperature sensor that measures a temperature of a pump; and temperature control that controls a heater and/or a cooling device in such a manner that the temperature measured by the temperature sensor repeatedly changes back and forth between an upper limit and a lower limit, wherein the temperature control has a specified time that is set so as to include an elapsed time in which the temperature changes from the upper limit to the lower limit following said upper limit and an elapsed time in which the temperature changes from the lower limit to the upper limit following said upper limit during a normal operation of the vacuum pump, and, when the specified time elapses without confirming a change in a state of the upper limit or the lower limit, the temperature control forcibly controls the heater and/or the cooling device to change the state and/or to notify abnormality.

In the temperature control, the specified time is set so as to include an elapsed time in which the temperature changes from the upper limit to the next lower limit and an elapsed time in which the temperature changes from the lower limit to the next upper limit during the normal operation.

When the temperature sensor operates normally, the control is performed repeatedly between the upper limit and the lower limit. For this reason, the specified time is not exceeded.

However, when the specified time is exceeded without being able to confirm the change in the state of the upper limit or lower limit, it is determined that abnormality has occurred in a temperature sensor system. In this case, the control of the heater and/or the cooling device is forcibly carried out, to change the state of the upper limit or the lower limit. As a result, the operation of the pump can be sustained safely. In addition, the abnormality can be notified. The determination can be realized by means of software processing without the need for a separate temperature sensor for monitoring abnormality.

Furthermore, the present disclosure is a disclosure of a vacuum pump, wherein the specified time is set so as to include an elapsed time in which the temperature is lower than the lower limit, and an elapsed time in which the temperature exceeds the upper limit.

Not only can a risk of failure in the temperature sensor system arise between the two temperature thresholds of the upper limit and the lower limit, but also failure of the temperature sensor system is conceivable even in areas where the measured temperature is lower than the lower limit and areas where the measured temperature is higher than the upper limit. Thus, breakage of the temperature sensor system can be detected in all temperature ranges.

Furthermore, the present disclosure is a disclosure of a temperature control device that controls an object to be temperature-controlled, a temperature sensor that measures a temperature of the object, and, so that the temperature measured by the temperature sensor repeatedly changes back and forth between an upper limit and a lower limit, a heater and/or a cooling device, wherein the temperature control device has a specified time that is set so as to include an elapsed time in which the temperature changes from the upper limit to the lower limit following said upper limit and an elapsed time in which the temperature changes from the lower limit to the upper limit following said lower limit during a normal operation, and, when the specified time elapses without confirming a change in a state of the upper limit or the lower limit, the temperature control device forcibly controls the heater and/or the cooling device to change the state and/or to notify abnormality.

According to the present disclosure described above, when the specified time elapses without confirming a change in the state of the upper limit and/or the lower limit, the temperature control forcibly controls the heater and/or the cooling device to change the state and/or to notify the abnormality. Thus, the operation of the pump can be sustained safely. In addition, abnormality can be notified. The determination can be realized by means of software processing without the need for a separate temperature sensor for monitoring abnormality.

