High frequency power supply device and high frequency power supply method

A device includes an amplifier for amplifying and supplying a high frequency power supplied to a load, a parameter detector for detecting a parameter of a current, a voltage, or a power from the amplifier to the load, a current supply unit for supplying a driving current for the amplifier, and an output unit for outputting a command signal for changing an amplification degree of the amplifier based on the detected parameter such that the parameter becomes a target value. The device further includes a first abnormality detector for detecting an abnormality by monitoring the command signal, and/or a current detector for detecting the driving current, a current data storage unit storing an upper and a lower limit value of the driving current, and a second abnormality detector for detecting the abnormality based on at least one of the upper limit value or the lower limit value.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2019-061350, filed on Mar. 27, 2019, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a high frequency power supply device and a high frequency power supply method.

BACKGROUND

In a semiconductor device manufacturing process, for example, a plasma processing apparatus for performing film formation or etching on a substrate using plasma has been proposed. The plasma processing apparatus includes, e.g., a high frequency power supply device for supplying a high frequency power amplified by an amplifier to a plasma electrode. A processing gas is supplied into, e.g., a processing chamber and the high frequency power is supplied to the plasma electrode to generate a high frequency electric field in the processing chamber. Then, the plasma of the processing gas is generated and plasma treatment is performed on the substrate using the generated plasma.

For example, Japanese Patent Application Publication No. 2018-143368 discloses a high frequency power supply device including a plurality of vacuum tubes connected in parallel. The high frequency power supply device includes a voltage calculation unit for calculating a voltage change rate of each vacuum tube with respect to an average value of cathode voltages of the parallel-connected vacuum tubes and a current calculation unit for calculating a current change rate of each vacuum tube with respect to an average value of currents of the parallel-connected vacuum tubes. Then, it is determined whether or not each vacuum tube has reached the end of its lifespan by comparing the voltage change rate of each vacuum tube with a voltage lifespan setting value and comparing the current change rate of each vacuum tube with a current lifespan setting value.

The present disclosure provides a technique for detecting deterioration of an amplifier or abnormality (defect) of a detector in supplying a high frequency power.

SUMMARY

In accordance with an aspect of the present disclosure, there is provided a high frequency power supply device including: an amplifier configured to amplify a high frequency supplied from an oscillator and supply a high frequency power therefrom to a load; a parameter detector configured to detect a parameter of a current, a voltage, or a power supplied from the amplifier to the load; a current supply unit configured to supply a driving current for driving the amplifier; and a command signal output unit configured to output a command signal for changing an amplification degree of the amplifier based on the detected parameter such that the parameter becomes a target value. The high frequency power supply device further includes a first abnormality detector configured to detect an abnormality by monitoring the command signal, and/or the high frequency power supply device further includes a current detector configured to detect the driving current, a current data storage unit configured to store an upper limit value and a lower limit value of the driving current, and a second abnormality detector configured to detect the abnormality based on at least one of the upper limit value or the lower limit value of the driving current.

DETAILED DESCRIPTION

Hereinafter, a high frequency power supply device according to an embodiment of the present disclosure will be described. As shown inFIG. 1, a high frequency power supply device1is configured to amplify a high frequency power using an amplifier2and to supply the amplified high frequency power to a load4. The amplifier2serving as a rear-stage amplifier is formed by combining a plurality of transistors. A reference numeral ‘22’ inFIG. 1denotes a current supply unit for supplying a DC current as a driving current to the amplifier2. In this example, the high frequency power supply device1measures a high frequency power inputted to the load4, and the high frequency power supply device1increases or decreases an amplification factor of the amplifier2based on the measured high frequency power to adjust the high frequency power to a set target value.

As shown inFIG. 1, the high frequency power supply device1includes a power detector6for measuring a high frequency power. The power detector6is an example of a parameter detector. The power detector6measures a voltage at a high frequency and calculates a measured power value based on an amplitude of the voltage, for example.

Further, the high frequency power supply device1includes a controller (control device)5that is a command signal output unit. As will be described in detail later, the controller5outputs a digital signal that is a command signal for changing an amplification degree of a high frequency signal in an amplifying device3based on a difference between a target power value set by a host device100and a power value measured by the power detector6.

The high frequency power supply device1further includes a high frequency oscillator20and the amplifying device3for increasing and decreasing a high frequency output supplied from the high frequency oscillator20to the amplifier2. The amplifying device3serving as a front-stage amplifier includes a D/A converter31, an amplifier circuit32including transistors and the like. In the amplifying device3, a command value (command signal) that is a digital signal is converted to an analog voltage by the D/A converter31. The amplifier circuit32amplifies a high frequency signal with an amplification degree corresponding to the analog voltage.

In the high frequency power supply device1, the amplifier2may gradually deteriorate during the supply of the high frequency power and eventually malfunction. Conventionally, for example, a measured power value is monitored and an alarm is issued or the operation of the device is stopped when the measured power value becomes smaller than a threshold. However, the conventional control is performed based on whether or not the high frequency power supplied to the load4has decreased during the operation of the device. Therefore, the power supplied to the load4may become insufficient, which leads to the processing failure on the load4side. If the load4is a component of an apparatus for processing a semiconductor wafer W, as will be described later, the processing of the semiconductor wafer W becomes poor and the yield decreases. Further, if a component for replacement or a replacement work is prepared at the time when the amplifier2cannot be used due to malfunction, a long period of time is required to recover the high frequency power supply device1and the processing of the semiconductor wafer W is delayed during that period.

Therefore, in the high frequency power supply device1according to an embodiment of the present disclosure, the controller5monitors an adjusting amount to be described later and a current value of the driving current supplied from the current supply unit22to the amplifier2so that the deterioration of the amplifier2can be detected before the power outputted from the amplifier2decreases significantly.

FIG. 2is a block diagram showing the controller5. The controller5includes a CPU91, a power controller93A, an adjusting amount abnormality detector93B serving as a first abnormality detector, and a current abnormality detector93C serving as a second abnormality detector. A reference numeral ‘90’ inFIG. 2denotes a bus. The controller5further includes a memory92including a command value storage unit92A, an adjusting amount data storage unit92B, and a current data storage unit92C. An alarm unit94is connected to the controller5. A target power value is inputted from the host device100to the controller5, and a measured power value is inputted from the power detector6to the controller5. In addition, a current value is inputted from a current detector21, provided to detect a current value of a DC current for driving the amplifier2shown inFIG. 1, to the controller5.

The power controller93A outputs, as the adjusting amount, the digital signal based on the difference between the target power value inputted from the host device100and the measured power value inputted from the power detector6as described above. The digital signal is outputted such that the amplification factor in the amplifying device3increases (the adjusting amount increases) as the difference increases. As described above, the digital signal is outputted from the controller5and the amplification factor is changed by the change in the digital signal. However, for the sake of convenience in description, in graphs to be described later, it is assumed that the change in the digital signal is the change in the parameter of the analog signal value, and the parameter of the analog signal value will be described as the adjusting amount.

The adjusting amount abnormality detector93B of the present embodiment determines abnormality of the amplifier2based on the adjusting amount and an upper limit threshold and a lower limit threshold of the adjusting amount stored in the adjusting amount data storage unit92B.FIG. 3is a graph schematically showing a relational expression stored in the adjusting amount data storage unit92B. A hatched region inFIG. 3indicates values between a first upper limit threshold and a first lower limit threshold of the adjusting amount and dotted regions outside the hatched region indicate values between a second upper limit threshold and a second lower limit threshold of the adjusting amount.

A first lower limit threshold S1minof the adjusting amount is set based on a lower limit value of an adjusting amount that is obtained by, for example, controlling a high frequency power with the power controller93A when the high frequency power is outputted using a newly provided amplifier2while setting a target power value to a value of ‘P.’ A second lower limit threshold S2minof the adjusting amount, which is smaller than the first lower limit threshold S1min, is set based on a value of the adjusting amount at which it can be determined with certainty that the high frequency power supply device is malfunctioning.

A first upper limit threshold S1maxof the adjusting amount is set based on an upper limit value of an adjusting amount that is obtained by, for example, controlling a high frequency power with the power controller93A when a target power value is set to the value of ‘P’ and the high frequency power is outputted using an amplifier2that is able to output a sufficient high frequency voltage but has deteriorated through use. A second upper limit threshold S2maxof the adjusting amount, which is greater than the first upper limit threshold S1max, is set based on a value of the adjusting amount at which it can be determined that the amplifier2is malfunctioning.

In the high frequency power supply device1, when the target power value P increases, the amplification degree needs to be increased and, thus, the adjusting amount also increases. Therefore, the upper limit threshold and the lower limit threshold of the adjusting amount are set to become greater as the target power value P inputted from the host device100becomes greater.

The adjusting amount abnormality detector93B detects whether or not the abnormality has occurred by comparing the adjusting amount outputted from the amplifier circuit32with the first upper limit threshold S1max, the first lower limit threshold S1min, the second upper limit threshold S2max, and the second lower limit threshold S2minof the adjusting amount set based on the target power value P.

When the adjusting amount is greater than the first upper limit threshold S1maxor smaller than the first lower limit threshold S1min, the alarm unit94issues an alarm to notify the deterioration of the amplifier2. When the adjusting amount is greater than the second upper limit threshold S2maxor smaller than the second lower limit threshold S2min, the operation of the high frequency power supply device is stopped for maintenance such as the replacement of the amplifier2.

The current abnormality detector93C of the present embodiment determines whether or not the amplifier2is abnormal by comparing the current value of the driving current for driving the amplifier2with an upper limit threshold and a lower limit threshold of the current value stored in the current data storage unit92C.FIG. 4is a graph schematically showing a relational expression stored in the current data storage unit92C. A hatched region inFIG. 4indicates values between a first upper limit threshold and a first lower limit threshold of the current value, and dotted regions outside the hatched region indicate values between a second upper limit threshold and a second lower limit threshold of the current value.

A first lower limit threshold A1minof the current value is set based on a lower limit value of a current value that is obtained by, for example, controlling a high frequency power with the power controller93A when the high frequency power is outputted using a newly provided amplifier2while setting a target power value to a value of ‘P.’ A second lower limit threshold A2minof the current value, which is smaller than the first lower limit threshold A1min, is set based on a value of the current value at which it can be determined with certainty that the high frequency power supply device is malfunctioning.

A first upper limit threshold A1maxof the current value is set based on an upper limit value of a current value that is obtained by, for example, controlling a high frequency power with the power controller93A when a target power value is set to the value of ‘P’ and the high frequency power is outputted using an amplifier2that is able to output a sufficient high frequency voltage but has deteriorated through use. A second upper limit threshold A2maxof the current value, which is greater than the first upper limit threshold A1max, is set based on a value of the current value at which it can be determined that the amplifier2currently experiences malfunctions.

In the high frequency power supply device1, when the target power value P increases, the amplification degree needs to be increased and, thus, the current value also increases. Therefore, the upper limit threshold and the lower limit threshold of the current value are set to become greater as the target power value P inputted from the host device100becomes greater.

The current abnormality detector93C detects whether or not the abnormality has occurred by comparing the current value of the driving current supplied to the amplifier2with the first upper limit threshold A1max, the first lower limit threshold A1min, the second upper limit threshold A2max, and the second lower limit threshold A2minof the current value set based on the target power value P.

When the current value is greater than the first upper limit threshold A1maxor smaller than the first lower limit threshold A1min, the alarm unit94issues an alarm to notify the deterioration of the amplifier2. When the current value is greater than the second upper limit threshold A2maxor smaller than the second lower limit threshold A2min, the operation of the high frequency power supply device1is stopped for the maintenance such as the replacement of the amplifier2.

Hereinafter, the operation of the high frequency power supply device1according to the embodiment of the present disclosure will be described. When the high frequency power supply device1is powered on, the target power value P is inputted from the host device100to the controller5. At this time, the high frequency power is not supplied to the load4and, thus, the controller5outputs the adjusting amount to the amplifying device3based on the difference between the target power value P and the measured power value obtained by the power detector6. Then, the amplifying device3amplifies the high frequency with an amplification degree according to the adjusting amount and outputs the amplified high frequency to the amplifier2. The high frequency is further amplified by the amplifier2and the further amplified high frequency is outputted to the load4.

The adjusting amount abruptly increases and stabilizes to a constant value as the difference between the target power value P and the measured power value decreases. For example, after a predetermined period of time elapses from the start of outputting the command value from the controller5to the amplifying device3, the controller5obtains the adjusting amount at predetermined time intervals and calculates an average value of the obtained adjusting amounts. In the following description, the average value thus obtained is used as the adjusting amount used for comparison with the thresholds.

The adjusting amount abnormality detector93B compares the adjusting amount (the average value) with the upper limit threshold and the lower limit threshold of the preset adjusting amount set based on the target power value P. Further, the current value of the driving current of the amplifier2detected by the current detector21is inputted to the controller5. The current abnormality detector93C compares the current value with the upper limit threshold and the lower limit threshold of the set current value set based on the target power value P.

When the amplifier2is normally functioning without significant deterioration, the adjusting amount is in a range between the first upper limit threshold S1maxand the first lower limit threshold S1minof the preset adjusting amount corresponding to the target power value P shown inFIG. 3. Further, the current value is in a range between the first upper limit threshold A1maxand the first lower limit threshold A1maxof the preset current value corresponding to the target power value P shown inFIG. 4. Therefore, the supply of the high frequency power to the load4is continued without causing the alarm unit94to issue an alarm through the adjusting amount abnormality detector93B and the current abnormality detector93C.

However, the amplifier2gradually deteriorates while the high frequency power supply device1is being used. Therefore, the output of the high frequency power tends to be decreased with respect to the adjusting amount inputted to the amplifier2(that is, the high frequency power is not outputted in proportion to the adjusting amount). Accordingly, the difference between the target power value P and the measured power value increases, and the large value of the adjusting amount is outputted in order to increase the amplification degree in the amplifying device3. Further, due to the deterioration of the amplifier2, the resistance of the amplifier2increases and, thus, the current value of the driving current of the amplifier2increases.

If the degree of deterioration of the amplifier2further increases, the adjusting amount inputted to the amplifier2exceeds, e.g., the first upper limit threshold S1maxwhen the adjusting amount abnormality detector93compares the adjusting amount inputted to the amplifier2with the upper limit threshold and the lower limit threshold of the preset adjusting amount set based on the target power value P. Accordingly, the adjusting amount abnormality detector93causes the alarm unit94to issue an alarm to notify the deterioration of the amplifier2.

Further, for example, even when the adjusting amount inputted to the amplifier2is between the first upper limit threshold S1maxand the first lower limit threshold S1minof the adjusting amount, if the current value of the driving current of the amplifier2exceeds the first upper limit threshold A1maxof the preset current value set based on the target power value P, the alarm unit94issues an alarm to notify the deterioration of the amplifier2.

As described above, the alarm unit94issues an alarm when the adjusting amount inputted to the amplifier2exceeds a predetermined upper limit threshold or when the current value of the driving current of the amplifier2exceeds a predetermined upper limit threshold, so that a user can recognize the deterioration of the amplifier2. At this time, an adjusting amount greater than the upper limit threshold S1maxof the preset adjusting amount set based on the target power value P is inputted to the amplifier2. Therefore, the amplifier2receives the adjusting amount largely increased due to the deterioration. Therefore, although the amplifier2is deteriorated, a large amount of the high frequency power can be outputted therefrom. Thus, a sufficient amount of the high frequency power can be supplied to the load4. Accordingly, the user can recognize the deterioration of the amplifier2in a state where the sufficient amount of the high frequency power is supplied to the load4, so that an alternative device to the high frequency power supply device or a plan for stopping the process can be prepared.

Meanwhile, when the driving of the high frequency power supply device1is continued even after an alarm is issued by the alarm unit94, the adjusting amount corresponding to the target power value P further increases due to the progress of the deterioration of the amplifier2. Then, the adjusting amount eventually exceeds the second upper limit threshold S2max. At this time, the adjusting amount abnormality detector93B causes the alarm unit94to issue an alarm and the operation of the high frequency power supply device1is stopped.

Further, as the deterioration of the amplifier2progresses, the current value corresponding to the target power value P further increases. Therefore, the current value eventually exceeds the second upper limit threshold A2max. Accordingly, the current abnormality detector93C causes the alarm unit94to issue an alarm and the operation of the high frequency power supply device1is stopped.

For example, when the power detector6is defective, the measured power value may increase. In this case, the difference between the target power value P and the measured power value decreases and the command value decreases, so that the adjusting amount decreases.

In the present embodiment, when the adjusting amount is monitored, whether or not the adjusting amount is greater than or equal to the lower limit threshold of the amplification degree corresponding to the target power value P is also monitored. Therefore, in the case where the amplification degree is excessively small, if the adjusting amount becomes smaller than the first lower limit threshold S1min, the alarm unit94issues an alarm. Then, the user can recognize the defect of the power detector6. Further, when the adjusting amount becomes smaller than the second lower limit threshold S2min, the operation of the high frequency power supply device1is stopped.

Since the power outputted from the amplifier2decreases as the adjusting amount decreases, the current value of the driving current also decreases. In the high frequency power supply device1according to the embodiment of the present disclosure, when the current value is monitored, whether or not the current value is greater than equal to the lower limit threshold of the current value corresponding to the target power value P is also monitored. Accordingly, the defect of the power detector6can also be detected.

The above-described high frequency power supply device1of the present embodiment can be applied to, e.g., a plasma processing apparatus for performing plasma treatment on a semiconductor wafer (hereinafter, referred to as “wafer”) serving as a substrate. As shown inFIG. 5, the plasma processing apparatus40includes a processing chamber10, and a mounting table15for substantially horizontally mounting thereon the wafer W is disposed in the processing chamber10through a supporting column16. A reference numeral ‘11’ denotes a loading/unloading port for the wafer W that is formed at a side surface of the processing chamber10. A reference numeral ‘12’ denotes a gate valve. A vacuum exhaust unit14is connected to the processing chamber10through a gas exhaust line13.

A metal shower head17for supplying a processing gas for substrate processing toward the wafer W is disposed at a ceiling surface of the processing chamber10through an insulating member17a. The shower head17is configured to supply the processing gas from a processing gas supply source18into the processing chamber10. The high frequency power supply device1is connected to the shower head17through a matching unit19. Therefore, the shower head17in this example corresponds to the load4shown inFIG. 1.

In the plasma processing apparatus40, the processing gas is supplied into the processing chamber10in a vacuum atmosphere and the high frequency power is supplied to the shower head17to generate a high frequency electric field in the processing chamber10. Accordingly, plasma of the processing gas is generated and the wafer W is processed by the plasma thus generated. However, if the wafer W is processed without recognizing the deterioration of the high frequency power supply device1, e.g., the deterioration of the amplifier2, the amplifier2may experience the malfunction during the processing of the wafer W. If the malfunction of the amplifier2occurs during the processing of the wafer W, the high frequency electric field cannot be generated in the processing chamber10and the conversion of the processing gas to the plasma becomes insufficient. Accordingly, the processing of the wafer W becomes insufficient, thereby causing the defect of the wafer W.

By applying the high frequency power supply device1according to the embodiment of the present disclosure to the plasma processing apparatus40, the deterioration of the amplifier2can be detected before the malfunction of the amplifier2. Therefore, it is possible to suppress the generation of defective products due to the malfunction of the amplifier2during the processing of the wafer W. In addition, since the alternative high frequency power supply device1can be prepared or the product processing can be intentionally stopped before the malfunction of the amplifier2, unnecessary downtime caused by the malfunction during the processing of the wafer W can be reduced.

The load4is not limited to the shower head17and may be an electrode disposed at the mounting table15. The electrode to which the high frequency power is supplied is used for attracting ions in the plasma to the wafer W on the mounting table15.

In the above-described embodiment, the amplification degree of the amplifier2is controlled such that the high frequency power outputted from the high frequency power supply device1for amplifying a high frequency and supplying a high frequency power to the load4becomes a set target power value P. The adjusting amount of the amplification degree is monitored, and the alarm unit94issues an alarm when the adjusting amount is not in a range between the upper limit threshold and the lower limit threshold of the preset adjusting amount set to correspond to the target power value P. Further, the current value of the current for driving the amplifier2is monitored, and the alarm unit94issues an alarm when the current value is not in a range between the upper limit threshold and the lower limit threshold of the preset current value set to correspond to the target power value P. Accordingly, the deterioration of the amplifier2can be detected.

With the configuration including one of the adjusting amount abnormality detector93B for detecting the abnormality by monitoring the adjusting amount and the current abnormality detector93C for detecting the abnormality by detecting the current value of the amplifier2, it is possible to detect the deterioration of the amplifier2. However, the configuration including both of the adjusting amount abnormality detector93B and the current abnormality detector93C can further increase the accuracy in detecting the occurrence of the abnormality of the amplifier2.

The parameter detector may be a voltage detector for detecting a high frequency voltage outputted from the amplifier2or a current detector for detecting a high frequency current outputted from the amplifier2. The adjusting amount may be determined based on the detected current or the detected voltage, and the parameter detector may be configured to detect the occurrence of the abnormality based on the determined adjusting amount. When detecting the current, the detected current may be converted to a voltage to calculate the measured value, in the same manner as the case of detecting the power as described above. However, it is preferable to detect the power in order to improve accuracy.

When the amplifier2is in a normal state, the range between the upper limit threshold and the lower limit threshold of the adjusting amount inputted to the amplifier2varies depending on the target power value P. Further, when the amplifier2is in a normal state, the range between the upper limit threshold and the lower limit threshold of the current value of the driving current for driving the amplifier2varies depending on the target power value P.

For example, in the plasma processing apparatus, the processing time and the required target value P of the high frequency power may vary depending on recipes performed on the wafer W. Therefore, the appropriate range between the upper and the lower limit threshold of the adjusting amount and the appropriate range between the upper and the lower limit threshold of the current value of the driving current vary depending on the recipes. Accordingly, it is preferable to set, for each target power value P, the range between the upper and the lower limit threshold of the adjusting amount and the range between the upper and the lower limit threshold of the current value of the driving current.

Alternatively, for example, the range between the upper and the lower limit threshold of the adjusting amount and the range between the upper and the lower limit threshold of the current value of the driving current may be set for each recipe.

In the above-described Japanese Patent Application Publication No. 2018-143368, the deterioration state of the vacuum tube is detected based on the current supplied to the vacuum tube, whereas there is no process of detecting the occurrence of the abnormality by setting the upper and the lower limit threshold of the supplied current and comparing the supplied current with the upper and the lower limit threshold.

Further, the occurrence of the abnormality in the amplifier2may be detected based on changes in the temperature of the amplifier2. The power detector6, the controller5, the amplifying device3, a voltage supply source33, the high frequency oscillator20, and the amplifier2are disposed in a housing201. As shown inFIG. 6, the circuit constituting the amplifier2is included in, e.g., an integrated circuit chip200. The chip200is mounted on a circuit board202disposed in the housing201. A temperature sensor203is disposed on the surface of the chip200, so that the controller5can obtain the temperature detected by the temperature sensor203.

In this example, the controller5includes, e.g., a temperature storage unit92D storing an upper limit threshold and a lower limit threshold of the temperature detected by the temperature sensor203corresponding to the target power value P, and a third abnormality detector93D for comparing the temperature detected by the temperature sensor203with the upper limit threshold and the lower limit threshold of the detected temperature corresponding to the target power value P. The controller5shown inFIG. 6includes the temperature storage unit92D and the third abnormality detector93D in addition to the configuration of the controller5shown inFIG. 2that is not shown inFIG. 6.FIG. 7is a graph schematically showing a relational expression stored in the temperature storage unit92D. As described above, the temperature storage unit92D stores an upper limit temperature threshold Tmaxand a lower limit threshold Tminset for each target power value P.

For example, when the resistance of the circuit constituting the amplifier2increases due to the deterioration of the amplifier2, the heat generation increases and, thus, the detected temperature increases. Therefore, the temperature at which the deterioration of the amplifier2can be determined is stored as the upper limit threshold of the temperature for each target power value P. Further, the lower limit threshold of the range of the temperature detected when the amplifier2is functioning normally is stored as the lower limit threshold of the temperature corresponding to the target power value P.

The third abnormality detector93D causes the alarm unit94to issue an alarm when the temperature of the chip200exceeds the upper limit threshold of the temperature set to correspond to the target power value P. With this configuration, the deterioration of the amplifier can also be detected from the heat generated by the amplifier2. Accordingly, the deterioration of the amplifier2can be detected more reliably. In addition, the detected temperature may become lower than the lower limit threshold due to the defect of the temperature sensor203. In this case, the defect of the temperature sensor203can be estimated.

Similar to the range of the adjusting amount, it is possible to set a first upper limit threshold, a second upper limit threshold, a first lower limit threshold, and a second lower limit threshold of the range of the temperature detected by the temperature sensor203. Then, the alarm output and the operation stop of the high frequency power supply device can be separately performed based on the comparison result between the detected temperature and the thresholds. It is preferable to provide the temperature sensor203on the chip200because the changes in the operation state of the amplifier2can be accurately detected from the changes in the temperature as described above. However, as long as the temperature sensor203can detect the temperature corresponding to the temperature of the chip200constituting the amplifier2, the temperature sensor203may be disposed distant from the chip200in the housing201.

When the adjusting amount abnormality detector93B is used to detect the occurrence of the abnormality by monitoring the adjusting amount, it is not necessary to compare the adjusting amount with the upper limit threshold and the lower limit threshold of the adjusting amount corresponding to the power target value P. For example, it is also possible to measure the change rate of the adjusting amount per unit time and determine the deterioration of the amplifier2when the change rate of the adjusting amount exceeds a predetermined threshold.

In addition, the above-described control of monitoring the measured change rate of the adjusting amount per unit time may be combined with the conventional control of monitoring the measured power value and causing the alarm unit94to issue an alarm or stopping the operation of the device when the measured power value becomes smaller than a predetermined threshold.

Further, the D/A converter31of the amplifying device3may be included in the controller5. The amplifier2and the amplifying device3may be integrated, or each of them may be divided into two or more parts. In that case, the deterioration of each amplifier2and each amplifying device3may be detected in the above-described manner.

In this configuration, for the respective amplifiers2and the respective amplifying devices3, the measured current value or the measured adjusting amount that indicates the deterioration state of the respective amplifiers2and the respective amplifying devices3may be respectively added up and used for determining the abnormality based on the added current values or the added adjusting amounts.

In the above example, the amplification degree of the amplifier2is increased or decreased by increasing or decreasing a level of a gate signal while fixing a source voltage of a DC voltage (field effect transistor (FET)). However, the amplification degree of the amplifier2may be increased or decreased by increasing or decreasing the source voltage while fixing the level of the gate signal.

The embodiments of the present disclosure are illustrative in all respects and are not restrictive. The above-described embodiments can be embodied in various forms. Further, the above-described embodiments may be omitted, replaced, or changed in various forms without departing from the scope of the appended claims and the gist thereof.