Patent Publication Number: US-11031213-B2

Title: Microwave output device and plasma processing device

Description:
TECHNICAL FIELD 
     Embodiments of the present disclosure relate to a microwave output device and a plasma processing device. 
     BACKGROUND ART 
     A plasma processing device is used to manufacture an electronic device such as a semiconductor device. The plasma processing device includes various types of devices such as a capacitive coupling type plasma processing device and an inductive coupling type plasma processing device. In recent years, a plasma processing device of a type of exciting a gas by using microwaves has been used. 
     Patent Document 1 discloses a plasma processing device using microwaves. The plasma processing device includes a microwave output device outputting a microwave having a bandwidth. 
     Patent Document 2 discloses a microwave output device having a magnetron as a radio frequency oscillation source. The device includes a voltage control mechanism controlling a voltage to be applied to a radio frequency oscillator from a power supply. The voltage control mechanism includes a load control mechanism performing control such that a voltage corresponding to power obtained by adding power of a travelling wave of a microwave to power calculated on the basis of power of a reflected wave of the microwave is supplied to the radio frequency oscillator. 
     CITATION LIST 
     Patent Document 
     [Patent Document 1] Japanese Unexamined Patent Publication No. 2012-109080 
     [Patent Document 2] Japanese Unexamined Patent Publication No. 2014-154421 
     SUMMARY OF INVENTION 
     Technical Problem 
     It is necessary to generate stable plasma in manufacturing of an electronic device. The device disclosed in Patent Document 1 can stabilize plasma by output a microwave having a bandwidth. However, even when a microwave having a bandwidth is used, there is a condition in which plasma is unstable. 
     In order to realize stabilization of plasma, load control disclosed in Patent Document 2 may be applied to the device disclosed in Patent Document 1. Specifically, a device may be considered in which effective power supplied to a chamber main body is controlled to be constant while a microwave having a bandwidth is output. 
     However, the power of the microwave having a bandwidth disclosed Patent Document 1 is not constant, and the microwave normally has a waveform having different intensities. In the load control disclosed in Patent Document 2, it is necessary to stabilize microwave plasma by immediately supplying power when effective power of a microwave is reduced, and thus there is concern that power may not be immediately supplied. 
     Thus, there is a desire for a microwave output device and a plasma processing device capable of stably performing load control on a microwave having a bandwidth. 
     Solution to Problem 
     According to an aspect, there is provided a microwave output device. The microwave output device includes a microwave generation unit, an output portion, a first directional coupler, a second directional coupler, and a measurement unit. The microwave generation unit generates a microwave having a center frequency, power, and a bandwidth respectively corresponding to a setting frequency, setting power, and a setting bandwidth for which instructions are given from a controller. The output portion outputs the microwave propagating from the microwave generation unit. The first directional coupler outputs parts of travelling waves propagating toward the output portion from the microwave generation unit. The second directional coupler outputs parts of reflected waves returning to the output portion. The measurement unit determines first measured values indicating power levels of the travelling waves in the output portion on the basis of the parts of the travelling waves output from the first directional coupler, and determines second measured values indicating power levels of the reflected waves in the output portion on the basis of the parts of the reflected waves output from the second directional coupler. The microwave generation unit averages the first measured values and the second measured values at a predetermined movement average time and a predetermined sampling interval. The microwave generation unit controls a microwave such that a value obtained by subtracting the averaged second measured value from the averaged first measured value comes close to the setting power. The predetermined movement average time is 60 μs or less, and a relationship of y≥78.178x 0.1775  is satisfied when the predetermined sampling interval is indicated by x, and the predetermined movement average time is indicated by y. 
     The microwave output device controls the microwave such that a value obtained by subtracting the second measured values from the first measured values while generating the microwave having a bandwidth comes close to setting power. In other words, load control is performed on the microwave having a bandwidth. In this case, the microwave generation unit averages the first measured values and the second measured values at a predetermined movement average time and a predetermined sampling interval. In an averaging process, the predetermined movement average time is 60 μs or less. In the averaging process, a predetermined sampling interval x and a predetermined movement average time y satisfy a relationship of y≥78.178 0.1775 . A microwave is controlled such that a value obtained by subtracting the averaged second measured value from the averaged first measured value comes close to the setting power. The load control is performed under a condition in which a movement average time is 60 μs or less, and the relationship of y≥78.178x 0.1775  is satisfied, and thus it is possible to stably perform the load control on a microwave having a bandwidth. 
     In an embodiment, the measurement unit may include a first wave detection unit that generates an analog signal corresponding to power levels of the parts of the travelling waves by using diode wave detection; a first A/D converter that converts the analog signal generated by the first wave detection unit into a digital value; and a first processing unit that selects one or more first correction coefficients correlated with the setting frequency, the setting power, and the setting bandwidth for which instructions are given from the controller from among a plurality of first correction coefficients set in advance to correct the digital value generated by the first A/D converter to power of a travelling wave in the output portion, and determines the first measured values by multiplying the selected one or more first correction coefficients by the digital value generated by the first A/D converter. 
     The digital value obtained by converting an analog signal generated by the first wave detection unit in the first A/D converter has an error with respect to power of a travelling wave in the output portion. The error has dependency on a setting frequency, setting power, and a setting bandwidth of a microwave. In the microwave output device of the embodiment, a plurality of first correction coefficients are prepared in advance such that one or more first correction coefficients for reducing the error depending on a setting frequency, setting power, and a setting bandwidth are selectable. In the microwave output device, one or more first correction coefficients correlated with a setting frequency, setting power, and a setting bandwidth for which instructions are given from the controller are selected from among the plurality of first correction coefficients, and the one or more first correction coefficients are multiplied by a digital value generated by the first A/D converter, and thus the first measured value is obtained. Therefore, an error between power of a travelling wave in the output portion and the first measured value obtained on the basis of parts of travelling waves output from the first directional coupler is reduced. 
     In the embodiment, the measurement unit may include a second wave detection unit that generates an analog signal corresponding to power levels of the parts of the reflected waves by using diode wave detection; a second A/D converter that converts the analog signal generated by the second wave detection unit into a digital value; and a second processing unit that selects one or more second correction coefficients correlated with the setting frequency, the setting power, and the setting bandwidth for which instructions are given from the controller from among a plurality of second correction coefficients set in advance to correct the digital value generated by the second A/D converter to power of a reflected wave in the output portion, and determines the second measured values by multiplying the selected one or more second correction coefficients by the digital value generated by the second A/D converter. 
     The digital value obtained by converting an analog signal generated by the second wave detection unit in the second A/D converter has an error with respect to power of a reflected wave in the output portion. The error has dependency on a setting frequency, setting power, and a setting bandwidth of a microwave. In the microwave output device of the embodiment, a plurality of second correction coefficients are prepared in advance such that one or more second correction coefficients for reducing the error depending on a setting frequency, setting power, and a setting bandwidth are selectable. 
     In the microwave output device, one or more second correction coefficients correlated with a setting frequency, setting power, and a setting bandwidth for which instructions are given from the controller are selected from among the plurality of second correction coefficients, and the one or more second correction coefficients are multiplied by a digital value generated by the second A/D converter, and thus the second measured value is obtained. Therefore, an error between power of a reflected wave in the output portion and the second measured value obtained on the basis of parts of reflected waves output from the second directional coupler is reduced. 
     In the embodiment, the microwave generation unit may control the microwave such that the value obtained by subtracting the averaged second measured value from the averaged first measured value comes close to the setting power when a control mode for which an instruction is given from the controller is a first control mode, and control the microwave such that the averaged first measured value comes close to the setting power when a control mode for which an instruction is given from the controller is a second control mode. 
     As described above, the microwave generation unit can switch a control mode and can thus switch whether or not to perform load control according to a process condition. 
     In another aspect, there is provided a plasma processing device. The plasma processing device includes a chamber main body and the microwave output device. The microwave output device is configured to output a microwave for exciting a gas to be supplied to the chamber main body. The microwave output device is the microwave output device according to any one of the plurality of aspects and the plurality of embodiments. 
     Advantageous Effects of Invention 
     According to the various aspects and embodiments of the present disclosure, the microwave output device and the plasma processing device capable of stably performing load control on a microwave having a bandwidth are provided. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating a plasma processing device according to an embodiment. 
         FIG. 2  is a diagram illustrating a microwave output device of a first example. 
         FIG. 3  is a diagram illustrating a microwave output device of a second example. 
         FIG. 4  is a diagram illustrating a microwave generation principle in a waveform generator. 
         FIG. 5  is a diagram illustrating an example of a microwave generated by the waveform generator. 
         FIG. 6  is a diagram illustrating a first measurement unit of a first example. 
         FIG. 7  is a diagram illustrating a second measurement unit of the first example. 
         FIG. 8  is a diagram illustrating an example of a configuration regarding power feedback. 
         FIG. 9  is a diagram for describing an example of a movement average. 
         FIG. 10  is a flowchart illustrating an example of an operation of the plasma processing device. 
         FIG. 11  is a flowchart illustrating an example of a feedback process in a power control unit. 
         FIG. 12  is a graph indicating a relationship between power of a travelling wave of a microwave and time. 
         FIG. 13  is a graph indicating a relationship between power of a travelling wave of a microwave and time. 
         FIG. 14  is a graph illustrating a relationship between a movement average time and unsteadiness of power. 
         FIG. 15  is a graph illustrating a relationship between a sampling interval and a movement average time. 
         FIG. 16  is a graph illustrating a simulation result of power of a microwave. 
         FIG. 17  is a graph illustrating a simulation result of power of a microwave. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, with reference to the drawings, various embodiments will be described in detail. Identical or similar portions are given the same reference numeral throughout the drawings. 
     [Plasma Processing Device] 
       FIG. 1  is a diagram illustrating a plasma processing device according to an embodiment. As illustrated in  FIG. 1 , a plasma processing device  1  includes a chamber main body  12  and a microwave output device  16 . The plasma processing device  1  may further include a stage  14 , an antenna  18 , and a dielectric window  20 . 
     The chamber main body  12  provides a processing space S at the inside thereof. The chamber main body  12  includes a side wall  12   a  and a bottom portion  12   b . The side wall  12   a  is formed in an approximately cylindrical shape. A central axial line of the side wall  12   a  approximately matches an axial line Z which extends in a vertical direction. The bottom portion  12   b  is provided on a lower end side of the side wall  12   a . An exhaust hole  12   h  for exhaust is provided in the bottom portion  12   b . An upper end of the side wall  12   a  is an opening. 
     The dielectric window  20  is provided over the upper end of the side wall  12   a . The dielectric window  20  includes a lower surface  20   a  which faces the processing space S. The dielectric window  20  closes the opening in the upper end of the side wall  12   a . An O-ring  19  is interposed between the dielectric window  20  and the upper end of the side wall  12   a . The chamber main body  12  is more reliably sealed due to the O-ring  19 . 
     The stage  14  is accommodated in the processing space S. The stage  14  is provided to face the dielectric window  20  in the vertical direction. The stage  14  is provided such that the processing space S is provided between the dielectric window  20  and the stage  14 . The stage  14  is configured to support a workpiece WP (for example, a wafer) which is mounted thereon. 
     In an embodiment, the stage  14  includes a base  14   a  and an electrostatic chuck  14   c . The base  14   a  has an approximately disc shape, and is formed from a conductive material such as aluminum. A central axial line of the base  14   a  approximately matches the axial line Z. The base  14   a  is supported by a cylindrical support  48 . The cylindrical support  48  is formed from an insulating material, and extends from the bottom portion  12   b  in a vertically upward direction. A conductive cylindrical support  50  is provided on an outer circumference of the cylindrical support  48 . The cylindrical support  50  extends from the bottom portion  12   b  of the chamber main body  12  along the outer circumference of the cylindrical support  48  in a vertically upward direction. An annular exhaust path  51  is formed between the cylindrical support  50  and the side wall  12   a.    
     A baffle plate  52  is provided at an upper portion of the exhaust path  51 . The baffle plate  52  has an annular shape. A plurality of through-holes, which pass through the baffle plate  52  in a plate thickness direction, are formed in the baffle plate  52 . The above-described exhaust hole  12   h  is provided on a lower side of the baffle plate  52 . An exhaust device  56  is connected to the exhaust hole  12   h  through an exhaust pipe  54 . The exhaust device  56  includes an automatic pressure control valve (APC), and a vacuum pump such as a turbo-molecular pump. A pressure inside the processing space S may be reduced to a desired vacuum degree by the exhaust device  56 . 
     The base  14   a  also functions as a radio frequency electrode. A radio frequency power supply  58  for radio frequency bias is electrically connected to the base  14   a  through a feeding rod  62  and a matching unit  60 . The radio frequency power supply  58  outputs a constant frequency which is suitable to control ion energy which is inducted to the workpiece WP, for example, a radio frequency of 13.56 MHz with power which is set. The matching unit  60  accommodates a matching device configured to attain matching between impedance on the radio frequency power supply  58  side, and impedance mainly on a load side such as an electrode, plasma, and the chamber main body  12 . A blocking capacitor for self-bias generation is included in the matching device. 
     The electrostatic chuck  14   c  is provided on an upper surface of the base  14   a . The electrostatic chuck  14   c  holds the workpiece WP with an electrostatic suction force. The electrostatic chuck  14   c  includes an electrode  14   d , an insulating film  14   e , and an insulating film  14   f , and has an approximately disc shape. A central axial line of the electrostatic chuck  14   c  approximately matches the axial line Z. The electrode  14   d  of the electrostatic chuck  14   c  is configured with a conductive film, and is provided between the insulating film  14   e  and the insulating film  14   f . A DC power supply  64  is electrically connected to the electrode  14   d  through a switch  66  and a covered wire  68 . The electrostatic chuck  14   c  can suction and hold the workpiece WP by a coulomb&#39;s force which is generated by a DC voltage applied from the DC power supply  64 . A focus ring  14   b  is provided on the base  14   a . The focus ring  14   b  is disposed to surround the workpiece WP and the electrostatic chuck  14   c.    
     A coolant chamber  14   g  is provided at the inside of the base  14   a . For example, the coolant chamber  14   g  is formed to extend around the axial line Z. A coolant is supplied into the coolant chamber  14   g  from a chiller unit through a pipe  70 . The coolant, which is supplied into the coolant chamber  14   g , returns to the chiller unit through a pipe  72 . A temperature of the coolant is controlled by the chiller unit, and thus a temperature of the electrostatic chuck  14   c  and a temperature of the workpiece WP are controlled. 
     A gas supply line  74  is formed in the stage  14 . The gas supply line  74  is provided to supply a heat transfer gas, for example, a He gas to a space between an upper surface of the electrostatic chuck  14   c  and a rear surface of the workpiece WP. 
     The microwave output device  16  outputs a microwave which excites a process gas which is supplied into the chamber main body  12 . The microwave output device  16  is configured to variably adjust a frequency, power, and a bandwidth of the microwave. The microwave output device  16  may generate a microwave having a single frequency by setting, for example, a bandwidth of the microwave to substantially 0. The microwave output device  16  may generate a microwave having a bandwidth having a plurality of frequency components. Power levels of the plurality of frequency components may be the same as each other, and only a center frequency component in the bandwidth may have a power level higher than power levels of other frequency components. In an example, the microwave output device  16  may adjust the power of the microwave in a range of 0 W to 5000 W, may adjust the frequency or the center frequency of the microwave in a range of 2400 MHz to 2500 MHz, and may adjust the bandwidth of the microwave in a range of 0 MHz to 100 MHz. The microwave output device  16  may adjust a frequency pitch (carrier pitch) of the plurality of frequency components of the microwave in the bandwidth in a range of 0 to 25 kHz. 
     The plasma processing device  1  further includes a waveguide  21 , a tuner  26 , a mode converter  27 , and a coaxial waveguide  28 . An output unit of the microwave output device  16  is connected to one end of the waveguide  21 . The other end of the waveguide  21  is connected to the mode converter  27 . For example, the waveguide  21  is a rectangular waveguide. The tuner  26  is provided in the waveguide  21 . The tuner  26  has stubs  26   a  and  26   b . Each of the stubs  26   a  and  26   b  is configured to adjust a protrusion amount thereof with respect to an inner space of the waveguide  21 . The tuner  26  adjusts a protrusion position of each of the stubs  26   a  and  26   b  with respect to a reference position so as to match impedance of the microwave output device  16  with impedance of a load, for example, impedance of the chamber main body  12 . 
     The mode converter  27  converts a mode of the microwave transmitted from the waveguide  21 , and supplies the microwave having undergone mode conversion to the coaxial waveguide  28 . The coaxial waveguide  28  includes an outer conductor  28   a  and an inner conductor  28   b . The outer conductor  28   a  has an approximately cylindrical shape, and a central axial line thereof approximately matches the axial line Z. The inner conductor  28   b  has an approximately cylindrical shape, and extends on an inner side of the outer conductor  28   a . A central axial line of the inner conductor  28   b  approximately matches the axial line Z. The coaxial waveguide  28  transmits the microwave from the mode converter  27  to the antenna  18 . 
     The antenna  18  is provided on a surface  20   b  opposite to the lower surface  20   a  of the dielectric window  20 . The antenna  18  includes a slot plate  30 , a dielectric plate  32 , and a cooling jacket  34 . 
     The slot plate  30  is provided on a surface  20   b  of the dielectric window  20 . The slot plate  30  is formed from a conductive metal, and has an approximately disc shape. A central axial line of the slot plate  30  approximately matches the axial line Z. A plurality of slot holes  30   a  are formed in the slot plate  30 . In an example, the plurality of slot holes  30   a  constitute a plurality of slot pairs. Each of the plurality of slot pairs includes two slot holes  30   a  which extend in directions interesting each other and have an approximately elongated hole shape. The plurality of slot pairs are arranged along one or more concentric circles centering around the axial line Z. In addition, a through-hole  30   d , through which a conduit  36  to be described later can pass, is followed in the central portion of the slot plate  30 . 
     The dielectric plate  32  is formed on the slot plate  30 . The dielectric plate  32  is formed from a dielectric material such as quartz, and has an approximately disc shape. A central axial line of the dielectric plate  32  approximately matches the axial line Z. The cooling jacket  34  is provided on the dielectric plate  32 . The dielectric plate  32  is provided between the cooling jacket  34  and the slot plate  30 . 
     A surface of the cooling jacket  34  has conductivity. A flow passage  34   a  is formed at the inside of the cooling jacket  34 . A coolant is supplied to the flow passage  34   a . A lower end of the outer conductor  28   a  is electrically connected to an upper surface of the cooling jacket  34 . A lower end of the inner conductor  28   b  passes through a hole formed in a central portion of the cooling jacket  34  and the dielectric plate  32  and is electrically connected to the slot plate  30 . 
     A microwave from the coaxial waveguide  28  propagates through the inside of the dielectric plate  32  and is supplied to the dielectric window  20  from the plurality of slot holes  30   a  of the slot plate  30 . The microwave, which is supplied to the dielectric window  20 , is introduced into the processing space S. 
     The conduit  36  passes through an inner hole of the inner conductor  28   b  of the coaxial waveguide  28 . As described above, the through-hole  30   d , through which the conduit  36  can pass, is formed at the central portion of the slot plate  30 . The conduit  36  extends to pass through the inner hole of the inner conductor  28   b , and is connected to a gas supply system  38 . 
     The gas supply system  38  supplies a process gas for processing the workpiece WP to the conduit  36 . The gas supply system  38  may include a gas source  38   a , a valve  38   b , and a flow rate controller  38   c . The gas source  38   a  is a gas source of the process gas. The valve  38   b  switches supply and supply stoppage of the process gas from the gas source  38   a . For example, the flow rate controller  38   c  is a mass flow controller, and adjusts a flow rate of the process gas from the gas source  38   a.    
     The plasma processing device  1  may further include an injector  41 . The injector  41  supplies a gas from the conduit  36  to a through-hole  20   h  which is formed in the dielectric window  20 . The gas, which is supplied to the through-hole  20   h  of the dielectric window  20 , is supplied to the processing space S. The process gas is excited by a microwave which is introduced into the processing space S from the dielectric window  20 . According to this, plasma is generated in the processing space S, and the workpiece WP is processed by active species such as ions and/or radicals from the plasma. 
     The plasma processing device  1  further includes a controller  100 . The controller  100  collectively controls respective units of the plasma processing device  1 . The controller  100  may include a processor such as a CPU, a user interface, and a storage unit. 
     The processor executes a program and a process recipe which are stored in the storage unit so as to collectively control respective units such as the microwave output device  16 , the stage  14 , the gas supply system  38 , and the exhaust device  56 . 
     The user interface includes a keyboard or a touch panel with which a process manager performs a command input operation and the like so as to manage the plasma processing device  1 , a display which visually displays an operation situation of the plasma processing device  1  and the like. 
     The storage unit stores control programs (software) for realizing various kinds of processing executed by the plasma processing device  1  by a control of the processor, a process recipe including process condition data and the like, and the like. The processor calls various kinds of control programs from the storage unit and executes the control programs in correspondence with necessity including an instruction from the user interface. Desired processing is executed in the plasma processing device  1  under the control of the processor. 
     [Configuration Example of Microwave Output Device  16 ] 
     Hereinafter, two examples of the microwave output device  16  will be described in detail. 
     [First Example of Microwave Output Device  16 ] 
       FIG. 2  is a diagram illustrating a microwave output device of a first example. As illustrated in  FIG. 2 , the microwave output device  16  includes a microwave generation unit  16   a , a waveguide  16   b , a circulator  16   c , a waveguide  16   d , a waveguide  16   e , a first directional coupler  16   f , a first measurement unit  16   g  (an example of a measurement unit), a second directional coupler  16   h , a second measurement unit  16   i  (an example of a measurement unit), and a dummy load  16   j.    
     The microwave generation unit  16   a  includes a waveform generation unit  161 , a power control unit  162 , an attenuator  163 , an amplifier  164 , an amplifier  165 , and a mode converter  166 . The waveform generation unit  161  generates a microwave. The waveform generation unit  161  is connected to the controller  100  and the power control unit  162 . A microwave having a frequency (center frequency), a bandwidth, and a carrier pitch respectively corresponding to a setting frequency, a setting between, and a setting pitch designated by the controller  100  is generated. When the controller  100  designates power levels of a plurality of frequency components in a bandwidth via the power control unit  162 , the waveform generation unit  161  may generate a microwave including a plurality of frequency components respectively having power levels in which the power levels of the plurality of frequency components designated by the controller  100  are reflected. 
     An output of the waveform generation unit  161  is connected to the attenuator  163 . The attenuator  163  is connected to the power control unit  162 . The power control unit  162  may be, for example, a processor. The power control unit  162  controls an attenuation rate (attenuation amount) of a microwave in the attenuator  163  such that a microwave having power corresponding to setting power designated by the controller  100  is output from the microwave output device  16 . An output of the attenuator  163  is connected to the mode converter  166  via the amplifier  164  and the amplifier  165 . Each of the amplifier  164  and the amplifier  165  amplifies a microwave at a predetermined amplification rate. The mode converter  166  converts a propagation mode of a microwave output from the amplifier  165  from TEM into TE01. A microwave, which is generated through the mode conversion in the mode converter  166 , is output as an output microwave of the microwave generation unit  16   a.    
     An output of the microwave generation unit  16   a  is connected to one end of the waveguide  16   b . The other end of the waveguide  16   b  is connected to a first port  261  of the circulator  16   c . The circulator  16   c  includes a first port  261 , a second port  262 , and a third port  263 . The circulator  16   c  outputs a microwave, which is input to the first port  261 , from the second port  262 , and outputs a microwave, which is input to the second port  262 , from the third port  263 . One end of the waveguide  16   d  is connected to the second port  262  of the circulator  16   c . The other end of the waveguide  16   d  is an output portion  16   t  of the microwave output device  16 . 
     One end of the waveguide  16   e  is connected to the third port  263  of the circulator  16   c . The other end of the waveguide  16   e  is connected to the dummy load  16   j . The dummy load  16   j  receives a microwave which propagates through the waveguide  16   e  and absorbs the microwave. For example, the dummy load  16   j  converts the microwave into heat. 
     The first directional coupler  16   f  is configured to branch parts of microwaves (that is, travelling waves) which are output from the microwave generation unit  16   a  and propagate to the output portion  16   t , and to output the parts of the travelling waves. The first measurement unit  16   g  determines a first measured value indicating power of a travelling wave in the output portion  16   t  on the basis of the parts of the travelling waves output from the first directional coupler  16   f.    
     The second directional coupler  16   h  is configured to branch parts of reflected waves transmitted to the third port  263  of the c 16   c  with respect to microwaves (that is, reflected waves) which return to the output portion  16   t , and to output the parts of the reflected waves. The second measurement unit  16   i  determines a second measured value indicating power of a reflected wave in the output portion  16   t  on the basis of the parts of the reflected waves output from the second directional coupler  16   h.    
     The first measurement unit  16   g  and the second measurement unit  161  are connected to the power control unit  162 . The first measurement unit  16   g  outputs the first measured value to the power control unit  162 , and the second measurement unit  16   i  outputs the second measured value to the power control unit  162 . The power control unit  162  controls the attenuator  163  such that a difference between the first measured value and the second measured value, that is, load power (effective power) matches setting power designated by the controller  100 , and controls the waveform generation unit  161  as necessary. 
     In the first example, the first directional coupler  16   f  is provided between one end and the other end of the waveguide  16   b . The second directional coupler  16   h  is provided between one end and the other end of the waveguide  16   e.    
     [Second Example of Microwave Output Device  16 ] 
       FIG. 3  is a diagram illustrating a microwave output device of a second example. As illustrated in  FIG. 3 , the microwave output device  16  of the second example is different from the microwave output device  16  of the first example in that a measurement unit  16   k  (an example of a measurement unit) into which the first measurement unit  16   g  and the second measurement unit  16   i  are integrated is provided, and other configurations are the same. 
     [Details of Constituent Elements of Microwave Output Device] 
     [Details of Waveform Generation Unit] 
       FIG. 4  is a view illustrating a microwave generation principle in the waveform generation unit. As illustrated in  FIG. 4 , for example, the waveform generation unit  161  includes a phase locked loop (PLL) oscillator which can cause a microwave of which a phase is synchronized with that of a reference frequency to oscillate, and an IQ digital modulator which is connected to the PLL oscillator. The waveform generation unit  161  sets a frequency of a microwave which oscillates in the PLL oscillator to a setting frequency designated by the controller  100 . The waveform generation unit  161  modulates a microwave from the PLL oscillator, and a microwave having a phase difference with the microwave from the PLL oscillator by 90° by using the IQ digital modulator. Consequently, the waveform generation unit  161  generates a microwave having a plurality of frequency components in a bandwidth or a microwave having a single frequency. 
     The waveform generation unit  161  may perform inverse discrete Fourier transform on, for example, N complex data symbols so as to generate a continuous signal and thus to generate a microwave having a plurality of frequency components. A method of generating such a signal may be a method such as an orthogonal frequency division multiple access (OFDMA) modulation method used for digital TV broadcasting (for example, refer to Japanese Patent No. 5320260). 
     In an example, the waveform generation unit  161  has waveform data expressed by a digitalized code sequence in advance. The waveform generation unit  161  quantizes the waveform data, and applies the inverse Fourier transform to the quantized data so as to generate I data and Q data. The waveform generation unit  161  applies digital/analog (D/A) conversion to each of the I data and the Q data so as to obtain two analog signals. The waveform generation unit  161  inputs the analog signals to a low-pass filter (LPF) through which only a low frequency component passes. The waveform generation unit  161  mixes the two analog signals, which are output from the LPF, with a microwave from the PLL oscillator and a microwave having a phase difference with the microwave from the PLL oscillator by 90°, respectively. The waveform generation unit  161  combines microwaves which are generated through the mixing with each other. Consequently, the waveform generation unit  161  generates a microwave having a single frequency component or a plurality of frequency components. 
       FIG. 5  is a diagram illustrating an example of a microwave generated by the waveform generation unit. As illustrated in  FIG. 5 , the waveform generation unit  161  generates a microwave having power, a center frequency, and a bandwidth (BB width) respectively corresponding to setting power, a setting frequency, and a setting bandwidth for which instructions are given from the controller  100 . 
     [Example of First Measurement Unit  16   g ] 
       FIG. 6  is a diagram illustrating a first measurement unit of a first example. As illustrated in  FIG. 6 , in the first example, the first measurement unit  16   g  includes a first wave detection unit  200 , a first A/D converter  205 , and a first processing unit  206 . The first wave detection unit  200  generates an analog signal corresponding to power of parts of travelling waves output from the first directional coupler  16   f  by using diode wave detection. The first wave detection unit  200  includes a resistive element  201 , a diode  202 , a capacitor  203 , and an amplifier  204 . One end of the resistive element  201  is connected to an input of the first measurement unit  16   g . Parts of travelling waves output from the first directional coupler  16   f  are input to the input. The other end of the resistive element  201  is connected to the ground. The diode  202  is, for example, a low barrier Schottky diode. An anode of the diode  202  is connected to the input of the first measurement unit  16   g . A cathode of the diode  202  is connected to an input of the amplifier  204 . The cathode of the diode  202  is connected to one end of the capacitor  203 . The other end of the capacitor  203  is connected to the ground. An output of the amplifier  204  is connected to an input of the first A/D converter  205 . An output of the first A/D converter  205  is connected to the first processing unit  206 . 
     In the first measurement unit  16   g  of the first example, an analog signal (voltage signal) corresponding to power of parts of travelling waves from the first directional coupler  16   f  is obtained through rectification in the diode  202 , smoothing in the capacitor  203 , and amplification in the amplifier  204 . The analog signal is converted into a digital value P fd  in the first A/D converter  205 . The digital value P fd  has a value corresponding to power of the parts of the travelling waves from the first directional coupler  16   f . The digital value P fd  is input to the first processing unit  206 . 
     The first processing unit  206  is configured with a processor such as a CPU. The first processing unit  206  is connected to a storage device  207 . The storage device  207  stores a plurality of first correction coefficients for correcting the digital value P fd  to power of a travelling wave in the output portion  16   t . In the first processing unit  206 , a setting frequency F set , setting power P set , and a setting bandwidth W set  designated for the microwave generation unit  16   a  are designated by the controller  100 . The first processing unit  206  selects one or more first correction coefficients correlated with the setting frequency F set , the setting power P set , and the setting bandwidth W set  from among the plurality of first correction coefficients, and determines a first measured value P fm  by multiplying the selected first correction coefficients by the digital value P fd . 
     As an example, a plurality of preset first correction coefficients k f (F,P,W) are stored in the storage device  207 . Here, F indicates a frequency, and the number of F is the number of a plurality of frequencies which can be designated for the microwave generation unit  16   a . P indicates power, and the number of P is the number of a plurality of power levels which can be designated for the microwave generation unit  16   a . W indicates a bandwidth, and the number of W is the number of a plurality of bandwidths which can be designated for the microwave generation unit  16   a . The plurality of bandwidths which can be designated for the microwave generation unit  16   a  also include a bandwidth of about 0. A microwave having a bandwidth of about 0 is a single-frequency microwave, that is, a single-mode (SP) microwave. 
     When the plurality of first correction coefficients k f (F,P,W) are stored in the storage device  207 , the first processing unit  206  selects k f (F set ,P set ,W set ), and determines the first measured value P fm  by performing calculation of P fm =k f (F set ,P set ,W set )×P fd . 
     As another example, a plurality of first coefficients k1 f (F), a plurality of second coefficients k2 f (P), and a plurality of third coefficients k3 f (W) are stored as the plurality of first correction coefficients in the storage device  207 . Here, F, P, and W are the same as F, P, and W in the first correction coefficients k f (F,P,W). 
     When the plurality of first coefficients k1 f (F), the plurality of second coefficients k2 f (P), and the plurality of third coefficients k3 f (W) are stored as the plurality of first correction coefficients in the storage device  207 , the first processing unit  206  selects k1 f (F set ), k2 f (P set ), and k3 f (W set ), and determines the first measured value P fm  by performing calculation of P fm =k1 f (F set )×k2 f (P set )×k3 f (W set )×P fd . 
     The digital value P fd  obtained by converting an analog signal generated by the first wave detection unit  200  of the first measurement unit  16   g  of the first example illustrated in  FIG. 6  in the first A/D converter  205  has an error with respect to power of a travelling wave in the output portion  16   t . The error has dependency on a setting frequency, setting power, and a setting bandwidth of a microwave. A factor of the dependency lies in diode wave detection. In the first measurement unit  16   g  of the first example, one or more first correction coefficients, that is, k f (F set ,P set ,W set ) or k1 f (F set ), k2 f (P set ), and k3 f (W set ) correlated with the setting frequency F set , the setting power P set , and the setting bandwidth W set  for which instructions are given from the controller  100  are selected from among a plurality of first correction coefficients which are prepared in advance to reduce the error. The selected one or more first correction coefficients are multiplied by the digital value P fd . Consequently, the first measured value P fm  is obtained. Therefore, an error between power of a travelling wave in the output portion  16   t  and the first measured value P fm , obtained on the basis of parts of travelling waves output from the first directional coupler  16   f  is reduced. 
     The number of a plurality of first correction coefficients k f (F,P,W) is a product of the number of frequencies which can be designated as a setting frequency, the number of power levels which can be designated as setting power, and the number of bandwidths which can be designated as a setting bandwidth. On the other hand, when a plurality of first coefficients k1 f (F), a plurality of second coefficients k2 f (P), and a plurality of third coefficients k3 f (W) are used, the number of a plurality of first correction coefficients is a sum of the number of a plurality of first coefficients k1 f (F), the number of a plurality of second coefficients k2 f (P), and the number of a plurality of third coefficients k3 f (W). Therefore, when a plurality of first coefficients k1 f (F), a plurality of second coefficients k2 f (P), and a plurality of third coefficients k3 f (W) are used, the number of a plurality of first correction coefficients can be reduced compared with a case of using a plurality of first correction coefficients k f (F,P,W). 
     When the correction is not performed, the microwave output device may not include the first processing unit  206 . 
     [First Example of Second Measurement Unit  16   i ] 
       FIG. 7  is a diagram illustrating a second measurement unit of the first example. As illustrated in  FIG. 7 , in the first example, the second measurement unit  16   i  includes a second wave detection unit  210 , a second A/D converter  215 , and a second processing unit  216 . In the same manner as the first wave detection unit  200 , the second wave detection unit  210  generates an analog signal corresponding to power of parts of reflected waves output from the second directional coupler  16   h  by using diode wave detection. The second wave detection unit  210  includes a resistive element  211 , a diode  212 , a capacitor  213 , and an amplifier  214 . One end of the resistive element  211  is connected to an input of the second measurement unit  16   i . Parts of reflected waves output from the second directional coupler  16   h  are input to the input. The other end of the resistive element  211  is connected to the ground. The diode  212  is, for example, a low barrier Schottky diode. An anode of the diode  212  is connected to the input of the second measurement unit  16   i . A cathode of the diode  212  is connected to an input of the amplifier  214 . The cathode of the diode  212  is connected to one end of the capacitor  213 . The other end of the capacitor  213  is connected to the ground. An output of the amplifier  214  is connected to an input of the second A/D converter  215 . An output of the second A/D converter  215  is connected to the second processing unit  216 . 
     In the second measurement unit  16   i  of the first example, an analog signal (voltage signal) corresponding to power of parts of reflected waves from the second directional coupler  16   h  is obtained through rectification in the diode  212 , smoothing in the capacitor  213 , and amplification in the amplifier  214 . The analog signal is converted into a digital value P rd  in the second A/D converter  215 . The digital value P rd  has a value corresponding to power of the parts of the reflected waves from the second directional coupler  16   h . The digital value P rd  is input to the second processing unit  216 . 
     The second processing unit  216  is configured with a processor such as a CPU. The second processing unit  216  is connected to a storage device  217 . The storage device  217  stores a plurality of second correction coefficients for correcting the digital value P rd  to power of a reflected wave in the output portion  16   t . In the second processing unit  216 , the setting frequency F set , setting power P set , and a setting bandwidth W set , designated for the microwave generation unit  16   a  are designated by the controller  100 . The second processing unit  216  selects one or more second correction coefficients correlated with the setting frequency F set , the setting power P set , and the setting bandwidth W set  from among the plurality of second correction coefficients, and determines a second measured value P rm  by multiplying the selected second correction coefficients by the digital value P rd . 
     As an example, a plurality of preset second correction coefficients k r (F,P,W) are stored in the storage device  217 . Here, F, P, and W are the same as F, P, and W in the first correction coefficients k f (F,P,W). 
     When the plurality of second correction coefficients k r (F,P,W) are stored in the storage device  217 , the second processing unit  216  selects k r (F set ,P set ,W set ), and determines the second measured value P rm  by performing calculation of P rm =k r (F set ,P set ,W set )×P rd . 
     As another example, a plurality of fourth coefficients k1 r (F), a plurality of fifth coefficients k2 r (P), and a plurality of sixth coefficients k3 r (W) are stored as the plurality of second correction coefficients in the storage device  217 . Here, F, P, and W are the same as F, P, and W in the first correction coefficients k r (F,P,W). 
     When the plurality of fourth coefficients k1 r (F), the plurality of fifth coefficients k2 r (P), and the plurality of sixth coefficients k3 r (W) are stored as the plurality of second correction coefficients in the storage device  217 , the second processing unit  216  selects k1 r (F set ), k2 r (P set ), and k3 r (W set ), and determines the second measured value P rm  by performing calculation of P rm =k1 r (F set )×k2 r (P set )×k3 r (W set )×P rd . 
     The digital value P rd  obtained by converting an analog signal generated by the second wave detection unit  210  of the second measurement unit  16   i  of the first example illustrated in  FIG. 7  in the second A/D converter  215  has an error with respect to power of a reflected wave in the output portion  16   t . The error has dependency on a setting frequency, setting power, and a setting bandwidth of a microwave. A factor of the dependency lies in diode wave detection. In the second measurement unit  16   i  of the first example, in order to reduce the error, one or more second correction coefficients, that is, k r (F set ,P set ,W set ), or k1 r (F set ), k2 r (P set ), and k3 r (W set ) correlated with the setting frequency F set , the setting power P set , and the setting bandwidth W set  for which instructions are given from the controller  100  are selected from among a plurality of second correction coefficients which are prepared in advance. The selected one or more second correction coefficients are multiplied by the digital value P rd . Consequently, the second measured value P rm  is obtained. Therefore, an error between power of a reflected wave in the output portion  16   t  and the second measured value P rm  obtained on the basis of parts of reflected waves output from the second directional coupler  16   h  is reduced. 
     The number of a plurality of second correction coefficients k r (F,P,W) is a product of the number of frequencies which can be designated as a setting frequency, the number of power levels which can be designated as setting power, and the number of bandwidths which can be designated as a setting bandwidth. On the other hand, when a plurality of fourth coefficients k1 r (F), a plurality of fifth coefficients k2 r (P), and a plurality of sixth coefficients k3 r (W) are used, the number of a plurality of fourth coefficients k1 r (F), the number of a plurality of fifth coefficients k2 r (P), and the number of a plurality of sixth coefficients k3 r (W). Therefore, a plurality of fourth coefficients k1 r (F), a plurality of fifth coefficients k2 r (P), and a plurality of sixth coefficients k3 r (W) are used, the number of a plurality of second correction coefficients can be reduced compared with a case of using a plurality of second correction coefficients k r (F,P,W). 
     When the correction is not performed, the microwave output device may not include the second processing unit  216 . 
     [Measurement Unit  16   k ] 
     As described above, the measurement unit  16   k  is configured by integrating the first measurement unit  16   g  with the second measurement unit  16   i . The measurement unit  16   k  has functions (the same functions) corresponding to the first measurement unit  16   g  and the second measurement unit  16   i.    
     [Example of Power Feedback] 
     In the microwave output device  16 , the power control unit  162  controls power of a microwave output from the microwave output device  16  such that a difference between the first measured value P fm  and the second measured value P rm , comes close to setting power designated by the controller  100 , and thus load power of a microwave supplied to a load coupled to the output portion  16   t  can be made close to the setting power. 
       FIG. 8  is a diagram illustrating an example of a configuration regarding power feedback. A difference between the first example and the second example of the microwave output device  16  is only whether or not the first measurement unit  16   g  and the second measurement unit  16   i  are integrated with each other. Therefore, hereinafter, the second example of the microwave output device  16  will be described as a representative. 
     As illustrated in  FIG. 8 , the power feedback is realized by the first directional coupler  16   f , the second directional coupler  16   h , the measurement unit  16   k , the power control unit  162 , and the attenuator  163 . 
     As described above, the first directional coupler  16   f  and the second directional coupler  16   h  are coupled to the measurement unit  16   k . The measurement unit  16   k  includes the first wave detection unit  200 , the first A/D converter  205 , the second wave detection unit  210 , and the second A/D converter  215 . In  FIG. 8 , the first processing unit  206  and the second processing unit  216  are not illustrated. 
     The first wave detection unit  200  obtains an analog signal (voltage signal) corresponding to power Pf of parts of travelling waves from the first directional coupler  16   f . The analog signal is converted into a digital value Pf(t) by the first A/D converter  205 . The second wave detection unit  210  obtains an analog signal (voltage signal) corresponding to power Pr of parts of reflected waves from the second directional coupler  16   h . The analog signal is converted into a digital value Pr(t) by the second A/D converter  215 . 
     The power control unit  162  includes a power processing unit  162   a , a storage unit  162   b , and a D/A converter  162   c.    
     The power processing unit  162   a  is configured with a processor such as a CPU. The power processing unit  162   a  is coupled to a storage device  314 . The power processing unit  162   a  acquires setting power, a setting frequency, a control mode (a PL mode (an example of a first control mode), a Pf mode (an example of a second control mode)), and a bandwidth (BB width) designated by the controller  100 . The power processing unit  162   a  acquires the digital value Pf(t) and the digital value Pr(t) from the measurement unit  16   k . When a control mode is the PL mode (an example of a first control mode), the power processing unit  162   a  sets the present value PM of a value to be controlled to a value obtained by subtracting the digital value Pr(t) from the digital value Pf(t). When a control mode is the Pr mode, the power processing unit  162   a  sets the present value PM of a value to be controlled to the digital value Pf(t). The power processing unit  162   a  compares the present value PM of a value to be controlled with the setting power, and adjusts an attenuation amount (attenuation rate) of the attenuator  163 . Consequently, load power of a microwave supplied to a load coupled to the output portion  16   t  can be made close to the setting power. 
     The attenuator  163  is a device which can changes an attenuation amount (attenuation rate) according to an applied voltage value as an example. The power processing unit  162   a  compares the present value PM of a value to be controlled with the setting power, thus determines an applied voltage value for the attenuator  163 , and outputs the applied voltage value to the attenuator  163  via the D/A converter  162   c . For example, when the digital value Pf(t) is the same as the setting power, the power processing unit  162   a  outputs an applied voltage value corresponding to power corresponding to a value obtained by adding the digital value Pf(t) to the digital value Pr(t). 
     [Example of Data Sampling in Power Processing Unit] 
       FIG. 9  is a diagram for describing an example of a movement average. In  FIG. 9 , a indicates a sampling interval [μs], b indicates a movement average time [μs] and c indicates the number of samples. The number of samples c is expressed by b/a. At a time point t=0, the power processing unit  162   a  acquires and averages c samples from Pf( 1 ) to Pf(c) at the sampling interval a. At a time point t=1, the power processing unit  162   a  acquires and averages c samples from Pf( 2 ) to Pf(c+1) at the sampling interval a. At a time point t=k, the power processing unit  162   a  acquires and averages c samples from Pf(k+1) to Pf(c+k) at the sampling interval a. This is expressed by equations as follows. 
     
       
         
           
             
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     Consequently, a power waveform having different intensities is averaged. In the above example, an example of a travelling wave has been described, but a reflected wave may be averaged in the same method. 
     [Operation of Plasma Processing Device] 
       FIG. 10  is a flowchart illustrating an example of the plasma processing device. The flowchart of  FIG. 10  is started, for example, when an operator of the plasma processing device  1  gives an instruction for outputting a microwave. 
     The controller  100  of the plasma processing device  1  sets a counter t to 0 as an initialization process (S 10 ). Subsequently, the controller  100  acquires power setting information (setting power, a center frequency, a modulation waveform (bandwidth), and a control mode) on the basis of an input operation from the operator or recipe information as a setting information acquisition process (S 12 ). 
     The controller  100  outputs a center frequency and a bandwidth of a microwave to the waveform generation unit  161  of the microwave output device  16  as a setting process (S 14 ). When the information is received, the waveform generation unit  161  generates a microwave having the set center frequency and bandwidth as a generation process (S 16 ). 
     Subsequently, the controller  100  outputs setting power, a center frequency, a modulation waveform (bandwidth), and a control mode of a microwave to the power control unit  162  of the microwave output device  16  as a power setting process. 
     The power control unit  162  performs a feedback process of power of a microwave as a feedback process (S 20 ). Details thereof will be described later. 
     Subsequently, the controller  100  determines whether or not a finish condition is satisfied as a finish determination (S 24 ). The finish condition is a finish condition of interrupting output of a microwave, and is set in advance. For example, the controller  100  determines whether or not the finish condition of interrupting output of a microwave is satisfied on the basis of a finish operation signal from an operator or recipe information. 
     When it is determined that the finish condition is not satisfied (S 24 : NO), the power control unit  162  performs the feedback process (S 20 ) again. When it is determined that the finish condition is satisfied (S 24 : YES), the plasma processing device  1  finishes the process illustrated in  FIG. 10 . 
     [Details of Feedback Process] 
       FIG. 11  is a flowchart illustrating an example of the feedback process in the power control unit. The flowchart of  FIG. 11  illustrates the feedback process (S 20 ) in  FIG. 10  in detail. 
     The power control unit  162  determines whether or not an elapsed time from the previous sampling has reached a sampling time a as a time determination process (S 200 ). When it is determined that the elapsed time has not reached the sampling time a (S 200 : NO), the power control unit  162  stands by for a predetermined period, and performs the time determination process (S 200 ) again. When it is determined that the elapsed time has reached the sampling time a (S 200 : YES), the power control unit  162  increments the counter t by 1 (t=t+1) as a count process (S 202 ). 
     Subsequently, the measurement unit (the first measurement unit  16   g  and the second measurement unit  16   i  or the measurement unit  16   k ) performs wave detection as a wave detection process (S 204 ). As an example, the first wave detection unit  200  of the measurement unit  16   k  obtains an analog signal (voltage signal) corresponding to the power Pf of parts of travelling waves from the first directional coupler  16   f . The analog signal is converted into a digital value Pf(t) by the first A/D converter  205 . The second wave detection unit  210  of the measurement unit  16   k  obtains an analog signal (voltage signal) corresponding to the power Pr of parts of reflected waves from the second directional coupler  16   h . The analog signal is converted into a digital value Pr(t) by the second A/D converter  215 . 
     Subsequently, the measurement unit (the first measurement unit  16   g  and the second measurement unit  16   i  or the measurement unit  16   k ) performs correction as a power correction process (S 206 ). For example, the measurement unit  16   k  selects one or more first correction coefficients, that is, k f (F set ,P set , W set ) or k1 f (F set ), k2 f (P set ), k3 f (W set ) respectively correlated with the setting frequency F set , the setting power P set , and the setting bandwidth W set  for which instructions are given from the controller  100 , from among a plurality of first correction coefficients prepared in advance. The measurement unit  16   k  multiplies the selected one or more first correction coefficients by the digital value P fd . Consequently, the first measured value P fm  is obtained. Similarly, the measurement unit  16   k  selects one or more second correction coefficients, that is, k r (F set ,P set ,W set ) or k1 r (F set ), k2 r (P set ), k3 r (W set ) respectively correlated with the setting frequency F set , the setting power P set , and the setting bandwidth W set  for which instructions are given from the controller  100 , from among a plurality of second correction coefficients prepared in advance. The measurement unit  16   k  multiplies the selected one or more second correction coefficients by the digital value P rd . Consequently, the second measured value P rm  is obtained. 
     Subsequent, the power control unit  162  calculates a movement average as a calculation process (S 208 ). The power control unit  162  calculates a movement average of the first measured value P fm  and the second measured value P rm  by using the equation described with reference to  FIG. 9 . 
     Subsequently, the power control unit  162  calculates the present value PM of a value to be controlled as a power calculation process (S 210 ). When a control mode is the PL mode (an example of a first control mode), the power processing unit  162   a  sets the present value PM of a value to be controlled to a value obtained by subtracting the second measured value P rm  from the first measured value P fm . On the other hand, when a control mode is a P f  mode, the power control unit  162  sets the present value PM of a value to be controlled to the first measured value P fm . 
     Subsequently, the power control unit  162  compares the present value PM with the setting power as a power determination process (S 212 ). When it is determined that the setting power is less than the present value PM (S 212 : YES), the power control unit  162  reduces an attenuation amount (attenuation rate) of the attenuator  163  as a reduction process (S 214 ). When it is determined that the setting power is not less than the present value PM (S 212 : NO), the power control unit  162  increases an attenuation amount (attenuation rate) of the attenuator  163  as an increase process (S 216 ). 
     When the reduction process (S 214 ) or the increase process (S 216 ) is finished, the plasma processing device  1  finishes the process illustrated in  FIG. 11 . 
     [Relationship Between Sampling Interval and Movement Average Time] 
       FIGS. 12 and 13  are graphs illustrating a relationship between power of a travelling wave of a microwave and time. A longitudinal axis of the graph expresses power of a travelling wave of a microwave, and a transverse axis expresses time. (A) of  FIG. 12  is a graph in a case where the sampling interval is 0.1 μs, and the movement average time is 0.1 μs, 20 μs, 50 μs, 80 μs, and 100 μs. (B) of  FIG. 12  is a graph in a case where the sampling interval is 0.5 μs, and the movement average time is 0.5 μs, 20 μs, 50 μs, 80 μs, and 100 μs. (C) of  FIG. 12  is a graph in a case where the sampling interval is 1.0 μs, and the movement average time is 1 μs, 20 μs, 50 μs, 80 μs, and 100 μs. (D) of  FIG. 13  is a graph in a case where the sampling interval is 5 μs, and the movement average time is 5 μs, 20 μs, 50 μs, 80 μs, and 100 μs. (E) of  FIG. 13  is a graph in a case where the sampling interval is 10 μs, and the movement average time is 10 μs, 20 μs, 50 μs, 80 μs, and 100 μs. 
     As illustrated in  FIGS. 12 and 13 , it is confirmed that a variation in a waveform is reduced regardless of a sampling time as a movement average time is increased. 
       FIG. 14  is a graph illustrating a relationship between a movement average time and unsteadiness of power. Source data for  FIG. 14  is the waveform data illustrated in  FIGS. 12 and 13 . In  FIG. 14 , a transverse axis expresses a movement average time, and a longitudinal axis expresses unsteadiness. The unsteadiness is defined by a value obtained by dividing a standard deviation by an average value.  FIG. 14  is a graph illustrating a relationship between a movement average time and unsteadiness of power for each sampling interval. 
     As illustrated in  FIG. 14 , as a movement average time is increased, a variation in a waveform tends to be reduced regardless of a sampling interval. On the other hand, in order to stabilize plasma, the unsteadiness of power is required to be reduced to 3% or less. In other words, plasma can be stabilized when a sampling interval and a movement average time satisfy a predetermined relationship. 
       FIG. 15  is a graph illustrating a relationship between a sampling interval and a movement average time. Source data for  FIG. 15  is the data illustrated in  FIG. 14 . In  FIG. 15 , a transverse axis expresses a movement average time, and a longitudinal axis expresses unsteadiness. Each piece of data is approximated by an approximate curve. For example, data of unsteadiness of 3% is approximated by y=78.178x 0.1775  which is an approximate curve. Here, power of which unsteadiness is equal to or less than 3% is data obtained in a range of y≥78.178x 0.1775  when the sampling interval is indicated by x, and the movement average time is indicated by y. A control operation starting time in the PL mode requires  60  and thus the movement average time is 60 μs or less. In other words, it is confirmed that plasma is stabilized when a sampling interval and a movement average time satisfy the relationship of y≥78.178x 0.1775  at the movement average time of 60 μs or less (a region TS in  FIG. 15 ). 
     [Simulation Results] 
       FIGS. 16 and 17  are graphs illustrating simulation results of power of a microwave. A longitudinal axis of the graph expresses power of a microwave, and a transverse axis expresses time. The graph illustrates a behavior of a power waveform when a sampling time is set to 0.1 μs, and a movement average time is increased. 
     In the simulation, setting power was 2000 W, and a value obtained by subtracting the power Pr of a reflected wave from the power Pf of a travelling wave was set as the load power PL (present value PM). The reflected wave power Pr was set to Pr=Pf/1000 at t&lt;0.05 (where t is time). The reflected wave power Pr was set to Pr=Pf/10 at t≥0.05 (where t is time). A sampling time and a movement average time were changed under the conditions, and the load power PL, the travelling wave power Pf, and the reflected wave power Pr were calculated. 
     (A) of  FIG. 16  illustrates waveforms of the load power PL, the travelling wave power Pf, and the reflected wave power Pr when the sampling interval is 0.1 μs, the movement average time is 0.1 μs, and the number of samples is 1. (B) of  FIG. 16  illustrates waveforms of the load power PL, the travelling wave power Pf, and the reflected wave power Pr when the sampling interval is 0.1 μs, the movement average time is 1 μs, and the number of samples is 10. (C) of  FIG. 16  illustrates waveforms of the load power PL, the travelling wave power Pf, and the reflected wave power Pr when the sampling interval is 0.1 μs, the movement average time is 10 μs, and the number of samples is 100. (D) of  FIG. 17  illustrates waveforms of the load power PL, the travelling wave power Pf, and the reflected wave power Pr when the sampling interval is 0.1 μs, the movement average time is 50 μs, and the number of samples is 500. (E) of  FIG. 17  illustrates waveforms of the load power PL, the travelling wave power Pf, and the reflected wave power Pr when the sampling interval is 0.1 μs, the movement average time is 100 μs, and the number of samples is 1000. 
     The unsteadiness (a value obtained by dividing a standard deviation by an average value) was calculated in each condition. The unsteadiness in (A) of  FIG. 16  was 56.2%, the unsteadiness in (B) of  FIG. 16  was 24.7%, the unsteadiness in (C) of  FIG. 16  was 7.5%, the unsteadiness in (D) of  FIG. 17  was 2.7%, and the unsteadiness in (E) of  FIG. 17  was 0.4%. Thus, it was confirmed that the unsteadiness is reduced to 3% or less under the conditions in (D) and (E) of  FIG. 17 . It was confirmed that the condition in (D) of  FIG. 17  satisfies the relationship of y≥78.178x 0.1775  at the movement average time of 60 μs or less. 
     [Advantageous Effects of Embodiment] 
     As mentioned above, the microwave output device  16  according to the embodiment controls a microwave such that a value obtained by subtracting the second measured values from the first measured values while generating the microwave having a bandwidth comes close to setting power. In other words, load control is performed on the microwave having a bandwidth. In this case, the microwave generation unit  16   a  averages the first measured values and the second measured values at a predetermined movement average time and a predetermined sampling interval. In an averaging process, the predetermined movement average time is 60 μs or less. In the averaging process, a predetermined sampling interval x and a predetermined movement average time y satisfy a relationship of y≥78.178x 0.1775 . A microwave is controlled such that a value obtained by subtracting the averaged second measured value from the averaged first measured value comes close to the setting power. The load control is performed under a condition in which a movement average time is 60 μs or less, and the relationship of y≥78.178x 0.1775  is satisfied, and thus it is possible to stably perform the load control on a microwave having a bandwidth. 
     In the microwave output device  16  according to the embodiment, a plurality of first correction coefficients are prepared in advance such that one or more first correction coefficients for reducing the error depending on a setting frequency, setting power, and a setting bandwidth are selectable. In the microwave output device  16 , one or more first correction coefficients correlated with a setting frequency, setting power, and a setting bandwidth for which instructions are given from the controller  100  are selected from among the plurality of first correction coefficients, and the one or more first correction coefficients are multiplied by a digital value generated by the first A/D converter, and thus the first measured value is obtained. Therefore, an error between power of a travelling wave in the output portion lot and the first measured value obtained on the basis of parts of travelling waves output from the first directional coupler  16   f  is reduced. 
     In the microwave output device  16  according to the embodiment, a plurality of second correction coefficients are prepared in advance such that one or more second correction coefficients for reducing the error depending on a setting frequency, setting power, and a setting bandwidth are selectable. In the microwave output device, one or more second correction coefficients correlated with a setting frequency, setting power, and a setting bandwidth for which instructions are given from the controller  100  are selected from among the plurality of second correction coefficients, and the one or more second correction coefficients are multiplied by a digital value generated by the second A/D converter, and thus the second measured value is obtained. Therefore, an error between power of a reflected wave in the output portion  16   t  and the second measured value obtained on the basis of parts of reflected waves output from the second directional coupler  16   h  is reduced. 
     In the microwave output device  16  according to the embodiment, the microwave generation unit  16   a  can switch a control mode and can thus switch whether or not to perform load control according to a process condition. 
     As mentioned above, various embodiments have been described, but various modifications may occur without limitation to the embodiments. 
     REFERENCE SIGNS LIST 
       1  PLASMA PROCESSING DEVICE,  12  CHAMBER MAIN BODY,  14  STAGE,  16  MICROWAVE OUTPUT DEVICE,  16   a  MICROWAVE GENERATION UNIT,  16   f  FIRST DIRECTIONAL COUPLER,  16   g  FIRST MEASUREMENT UNIT (EXAMPLE OF MEASUREMENT UNIT),  16   h  SECOND 
     DIRECTIONAL COUPLER,  16   i  SECOND MEASUREMENT UNIT (EXAMPLE OF MEASUREMENT UNIT),  16   k  MEASUREMENT UNIT (EXAMPLE OF MEASUREMENT UNIT),  16   t  OUTPUT PORTION,  18  ANTENNA,  20  DIELECTRIC WINDOW,  26  TUNER,  27  MODE CONVERTER,  28  COAXIAL WAVEGUIDE,  30  SLOT PLATE,  32  DIELECTRIC PLATE,  34  COOLING JACKET,  38  GAS SUPPLY SYSTEM,  58  RADIO FREQUENCY POWER SUPPLY,  60  MATCHING UNIT,  100  CONTROLLER,  161  WAVEFORM GENERATION UNIT,  162  POWER CONTROL UNIT,  163  ATTENUATOR,  164  AMPLIFIER,  165  AMPLIFIER,  166  MODE CONVERTER,  200  FIRST WAVE DETECTION UNIT,  202  DIODE,  203  CAPACITOR,  205  FIRST A/D CONVERTER,  206  FIRST PROCESSING UNIT,  207  STORAGE DEVICE,  210  SECOND WAVE DETECTION UNIT,  212  DIODE,  213  CAPACITOR,  215  SECOND A/D CONVERTER,  216  SECOND PROCESSING UNIT,  217  STORAGE DEVICE.