JP2016100312A - Plasma processing device and plasma processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma processing device and a plasma processing method which make possible to obtain a desired microwave oscillation frequency and spectrum characteristics with stability even at the beginning of a treatment in a process or in successively changing a process condition.SOLUTION: A plasma processing device for processing an object to be processed comprises: a process chamber for performing a plasma processing on an object to be processed loaded therein; a microwave oscillator 55; and a plasma-generating mechanism which uses microwaves emitted by the microwave oscillator 55 to generate plasma in the process chamber. The microwave oscillator 55 has: an output-distribution mechanism 106 which distributes one of outputs of microwaves emitted by the microwave oscillator 55 as an output for generating the plasma in the process chamber, and the other as an output to be absorbed by a dummy load 122 provided outside the process chamber; and a control part 110 which controls the distributing proportion of the microwave output distribution by the output-distribution mechanism 106.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a plasma processing apparatus and a plasma processing method.

  For example, in the manufacture of semiconductor devices, it is known that a plasma processing apparatus that excites plasma in a processing container using a microwave oscillator that oscillates microwaves is known. As the microwave oscillator, a magnetron that is inexpensive and can oscillate a high-output microwave is often used.

  In such a microwave oscillator, the characteristics of the oscillated microwave may vary from a desired desired characteristic due to various factors. For example, since a microwave oscillator has frequency dependence on output power, the frequency of the microwave oscillated (hereinafter also simply referred to as “oscillation frequency”) depends on the magnitude of the output power (output power). May vary. In addition, since the microwave oscillator is a machined product, the oscillation frequency varies from the desired frequency due to mechanical errors between the plurality of microwave oscillators, or the desired frequency cannot be obtained due to aging of the microwave oscillator. There is also.

  On the other hand, various techniques for adjusting the oscillation frequency fluctuating from a desired frequency have been studied. For example, a technique for adjusting an oscillation frequency to a desired frequency by providing an impedance generator at the subsequent stage of the microwave oscillator and changing the impedance applied to the microwave oscillator is known. Also known is a technique for fixing the oscillation frequency to the frequency of the reference signal by injecting into the microwave oscillator a reference signal having the same frequency as the desired frequency and lower than the output power of the microwave oscillator. Yes.

  It is also known that the output of a microwave oscillator (especially magnetron) is not a single frequency but has a certain spectrum width, and the spectrum characteristics (spectrum peak shape) are not easily constant.

  In recent years, in order to shorten processing time and increase efficiency, when using plasma processing equipment in the manufacture of semiconductor devices, etc., various processing steps using multiple types of gases are continuously performed while plasma discharge continues. It is known (see Patent Documents 1 and 2). In this case, since the processing conditions are different for each processing step, the output power of the microwave oscillator is also different for each processing condition, and it may be required to continuously change the output power.

JP 2007-287924 A JP 2011-165769 A

  As described above, the oscillation frequency of the microwave oscillator varies depending on the magnitude of the output power. Further, it has been known that it takes time for the oscillation frequency to stabilize when the output power is input to the microwave oscillator or when the output power to be input is continuously changed.

  Further, the spectrum characteristic at the oscillation frequency of the microwave oscillator also changes when the input power to be input is changed, and there is a problem that it takes time for the oscillation frequency to be stabilized. That is, when the process processing is started or when the process conditions are continuously changed, the frequency characteristics and the spectrum characteristics also vary, which may affect the process processing.

  In particular, in a processing apparatus that performs plasma processing using microwaves via a radial line slot antenna, it is known that the antenna has frequency characteristics. There is a risk of variations. Specifically, when the microwave is oscillated or when the output power is changed, the excitation state of the plasma changes due to the time required for the frequency to stabilize, such as a tuner for impedance matching. There is a concern that the position changes and the plasma generation mode changes.

  Furthermore, in the case of a magnetron as a microwave oscillator, when used at a low output power (for example, 500 W or less), the frequency of the oscillated microwave and its spectrum characteristics are not stable, and stable at a substantially low output power. There was a problem that it was difficult to use as a microwave oscillator.

  In view of the above circumstances, an object of the present invention is to continuously change process conditions at the start of process processing or in a plasma processing apparatus that excites plasma in a processing container using a microwave oscillator that oscillates microwaves. At the same time, it is an object of the present invention to provide a plasma processing apparatus and a plasma processing method capable of quickly and stably obtaining a desired microwave oscillation frequency and spectrum characteristics.

  Further, a plasma processing apparatus and plasma processing in which the microwave oscillation frequency and spectrum characteristics are constant regardless of the output power, and the microwave oscillation frequency and spectrum characteristics are constant even at a low output power of, for example, 500 W or less. It aims to provide a method.

  In order to achieve the above object, according to the present invention, there is provided a plasma processing apparatus for processing an object to be processed, which includes a processing vessel for accommodating the object to be processed and performing plasma processing, and a microwave oscillator, A plasma generation mechanism that generates plasma in the processing container using microwaves oscillated by the microwave oscillator, the microwave oscillator outputs an output of the microwave oscillated from the microwave oscillator, An output distribution mechanism that distributes an output for generating plasma in the processing container, and an output to be absorbed by a dummy load provided outside the processing container, and a control unit that controls an output distribution ratio of microwaves in the output distribution mechanism A plasma processing apparatus is provided.

  In the plasma processing apparatus, a matching unit including a directional coupler is provided between the output distribution mechanism and the processing container, and the directional coupler is provided in the processing container by the output distribution mechanism. A detector for detecting a power signal of a traveling wave of a microwave distributed to generate plasma is provided, and the control unit outputs a microwave in the output distribution mechanism based on the power signal detected by the detector. The distribution ratio may be controlled.

  In the plasma processing apparatus, a power source for supplying a voltage to the microwave oscillator is provided, and the control unit is configured based on an output distribution ratio of the microwave in the output distribution mechanism and a power signal detected by the detector. The voltage supplied to the microwave oscillator may be controlled.

  In the plasma processing apparatus, the plasma generation mechanism is provided with a dielectric window for transmitting the microwave generated by the microwave oscillator into the processing container and a plurality of slots, and the microwave is transmitted to the dielectric. And a slot antenna plate that radiates to the window.

  In the plasma processing apparatus, the output of the microwave oscillated from the microwave oscillator may be more than 500 W and not more than 5000 W. The microwave oscillator may include a magnetron.

  Further, according to the present invention from another viewpoint, a plasma is generated in the processing container using a microwave oscillated by the microwave oscillator, including a processing container for performing plasma processing inside and a microwave oscillator. A plasma processing method for processing a target object using a plasma processing apparatus comprising: a plasma generating mechanism for generating a microwave output oscillated from the microwave oscillator, one in the processing container An output distributing mechanism distributes the output for generating plasma and the other to be absorbed by a dummy load provided outside the processing container, and generates plasma in the processing container by using the microwave of the one output. A plasma processing method is provided, in which plasma processing is performed.

  In the plasma processing method, the processing of the object to be processed includes a plurality of continuous plasma processing steps, and the plurality of plasma processing steps use plasmas having different predetermined outputs, respectively, to generate plasma in the processing container. In the plurality of continuous plasma processing steps by controlling the microwave output distribution ratio in the output distribution mechanism by making the output of the microwave oscillated from the microwave oscillator constant. The output of the microwave for generating the signal may be continuously changed to a predetermined value for each step.

  In the plasma processing method, the output of the microwave oscillated from the microwave oscillator may be more than 500 W and not more than 5000 W. The microwave oscillator may include a magnetron.

According to the present invention, in a plasma processing apparatus that excites plasma in a processing container using a microwave oscillator that oscillates microwaves, when a process process is started or when process conditions are continuously changed, a desired value is obtained. It becomes possible to obtain the oscillation frequency and spectrum characteristics of the microwave quickly and stably.
Further, a plasma processing apparatus and plasma processing in which the microwave oscillation frequency and spectrum characteristics are constant regardless of the output power, and the microwave oscillation frequency and spectrum characteristics are constant even at a low output power of, for example, 500 W or less. A method can be realized.

It is a longitudinal cross-sectional view which shows the outline of a structure of the plasma processing apparatus concerning this Embodiment. It is a block diagram which shows the schematic structure of the microwave oscillator which concerns on this Embodiment. It is explanatory drawing explaining the fluctuation | variation of the oscillation frequency by output electric power. It is explanatory drawing about the dependence with respect to the individual difference of the spectrum of the microwave oscillated from a magnetron, and output power. It is explanatory drawing about the time-dependent fluctuation | variation of the frequency of the microwave oscillated from a magnetron, (a) is a time-dependent fluctuation | variation of the frequency with respect to single output electric power, (b) is output power continuously to several values. It shows the change over time of the frequency when changed. It is a schematic explanatory drawing which shows an example of a structure of an output distribution mechanism. It is a graph which shows the relationship between the position of the movable member in an output distribution mechanism, and the distribution ratio of the microwave propagated to an output end. It is explanatory drawing which compared the spectrum waveform of the microwave oscillated from the conventional magnetron, and the spectrum waveform of the microwave distributed by the output distribution mechanism which concerns on this Embodiment. It is a block diagram which shows the schematic structure of the microwave oscillator which concerns on other embodiment of this invention. It is a block diagram which shows schematic structure of the microwave oscillator which concerns on the 1st modification of this invention. It is a block diagram showing a schematic structure of a microwave oscillator concerning the 2nd modification of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted. In the plasma processing apparatus 1 according to the present embodiment, a plasma CVD (Chemical Vapor Deposition) process is performed on the surface of the wafer W as an object to be processed, and a SiN film (silicon nitride film) is formed on the surface of the wafer W. The case of forming will be described as an example.

  The plasma processing apparatus 1 has a processing container 10 as shown in FIG. The processing container 10 has a substantially cylindrical shape with an open ceiling surface, and a radial line slot antenna 40 to be described later is disposed in the opening on the ceiling surface. Further, a loading / unloading port 11 for the wafer W as an opening is formed on the side surface of the processing container 10, and a gate valve 12 is provided at the loading / unloading port 11. And the processing container 10 is comprised so that the inside can be sealed. The configurations of the loading / unloading port 11 and the gate valve 12 are simply illustrated in FIG. 1, and the detailed configuration will be described later with reference to FIG. In addition, metals, such as aluminum or stainless steel, are used for the processing container 10, and the processing container 10 is earth | grounded.

  On the bottom surface of the processing container 10, a mounting table 20 is provided as a mounting unit on which the wafer W is mounted. The mounting table 20 has a cylindrical shape, and the mounting table 20 is made of aluminum, for example.

  An electrostatic chuck 21 is provided on the upper surface of the mounting table 20. The electrostatic chuck 21 has a configuration in which an electrode 22 is sandwiched between insulating materials. The electrode 22 is connected to a DC power source 23 provided outside the processing container 10. This DC power source 23 can generate a Coulomb force on the surface of the mounting table 20 to electrostatically attract the wafer W onto the mounting table 20.

  Further, a high frequency power supply 25 for RF bias may be connected to the mounting table 20 via a capacitor 24. The high frequency power supply 25 outputs a predetermined frequency suitable for controlling the energy of ions drawn into the wafer W, for example, a high frequency of 13.56 MHz with a predetermined power.

  In addition, a temperature adjusting mechanism 26 that circulates a cooling medium, for example, is provided inside the mounting table 20. The temperature adjustment mechanism 26 is connected to a liquid temperature adjustment unit 27 that adjusts the temperature of the cooling medium. Then, the temperature of the refrigerant medium is adjusted by the liquid temperature adjusting unit 27, and the temperature of the mounting table 20 can be controlled. As a result, the wafer W mounted on the mounting table 20 can be maintained at a predetermined temperature. The mounting table 20 is provided with a gas passage (not shown) for supplying a heat transfer medium such as He gas at a predetermined pressure (back pressure) on the back surface of the wafer W.

  An annular focus ring 28 is provided on the upper surface of the mounting table 20 so as to surround the wafer W on the electrostatic chuck 21. For example, an insulating material such as ceramics or quartz is used for the focus ring 28, and the focus ring 28 acts to improve the uniformity of plasma processing.

  Below the mounting table 20, lifting pins (not shown) are provided for supporting the wafer W from below and lifting it. The elevating pins can be protruded from the upper surface of the mounting table 20 through a through hole (not shown) formed in the mounting table 20.

  Around the mounting table 20, an annular exhaust space 30 is formed between the mounting table 20 and the side surface of the processing container 10. An annular baffle plate 31 having a plurality of exhaust holes is provided above the exhaust space 30 in order to exhaust the inside of the processing container 10 uniformly. An exhaust pipe 32 is connected to the bottom of the exhaust space 30 and to the bottom surface of the processing container 10. The number of exhaust pipes 32 can be set arbitrarily, and a plurality of exhaust pipes 32 may be formed in the circumferential direction. The exhaust pipe 32 is connected to an exhaust device 33 provided with, for example, a vacuum pump. The exhaust device 33 can depressurize the atmosphere in the processing container 10 to a predetermined degree of vacuum.

  A radial line slot antenna 40 that supplies microwaves for plasma generation is provided at the ceiling surface opening of the processing vessel 10. The radial line slot antenna 40 includes a dielectric window (microwave transmission plate) 41, a slot plate 42, a slow wave plate 43, and a shield lid 44.

The dielectric window 41 is densely provided at the opening on the ceiling surface of the processing container 10 via a sealing material (not shown) such as an O-ring. Therefore, the inside of the processing container 10 is kept airtight. The dielectric window 41 is made of a dielectric material such as quartz, Al ₂ O ₃ , or AlN, and the dielectric window 41 transmits microwaves.

  The slot plate 42 is provided on the upper surface of the dielectric window 41 so as to face the mounting table 20. A plurality of slots are formed in the slot plate 42, and the slot plate 42 functions as an antenna. The slot plate 42 is made of a conductive material such as copper, aluminum, or nickel.

The slow wave plate 43 is provided on the upper surface of the slot plate 42. The slow wave plate 43 is made of a low-loss dielectric material such as quartz, Al ₂ O ₃ , or AlN, and the slow wave plate 43 shortens the wavelength of the microwave.

  The shield lid 44 is provided on the upper surface of the slow wave plate 43 so as to cover the slow wave plate 43 and the slot plate 42. A plurality of annular channels 45 through which a cooling medium flows, for example, are provided inside the shield lid 44. The dielectric window 41, the slot plate 42, the slow wave plate 43, and the shield cover 44 are adjusted to a predetermined temperature by the cooling medium flowing through the flow path 45.

  A coaxial waveguide 50 is connected to the center of the shield lid 44. The coaxial waveguide 50 has an inner conductor 51 and an outer tube 52. The inner conductor 51 is connected to the slot plate 42. The slot plate 42 side of the inner conductor 51 is formed in a conical shape so that microwaves can efficiently propagate to the slot plate 42.

  The coaxial waveguide 50 is connected in this order from the coaxial waveguide 50 side to a mode converter 53 that converts microwaves into a predetermined vibration mode, a rectangular waveguide 54, and a microwave oscillator 55 that oscillates microwaves. Has been. The microwave oscillator 55 oscillates a microwave having a predetermined frequency, for example, 2.45 GHz.

  With this configuration, the microwave oscillated by the microwave oscillator 55 sequentially propagates through the rectangular waveguide 54, the mode converter 53, and the coaxial waveguide 50, and is supplied into the radial line slot antenna 40, so that the retardation plate After being compressed by 43 and shortened in wavelength, circularly polarized waves are generated by the slot plate 42, the dielectric plate 41 is transmitted from the slot plate 42 and radiated into the processing chamber 10. The processing gas is converted into plasma in the processing chamber 10 by the microwave, and the plasma processing of the wafer W is performed by the plasma.

  The radial line slot antenna 40 (that is, the dielectric window 41, the slot plate 42, the slow wave plate 43, and the shield cover 44) and the microwave oscillator 55 are generally used as a plasma generation mechanism.

A first processing gas supply pipe 60 serving as a first processing gas supply unit is provided on the ceiling surface of the processing container 10, that is, on the central portion of the radial line slot antenna 40. The first processing gas supply pipe 60 penetrates the radial line slot antenna 40, and one end of the first processing gas supply pipe 60 is opened on the lower surface of the microwave transmission plate 41. Further, the first processing gas supply pipe 60 penetrates the inside of the inner conductor 51 of the coaxial waveguide 50 and further passes through the mode converter 53, and the other end portion of the first processing gas supply pipe 60. Is connected to a first processing gas supply source 61. For example, TSA (trisilylamine), N ₂ gas, H ₂ gas, and Ar gas are individually stored in the first processing gas supply source 61 as processing gases. Among these, TSA, N ₂ gas, and H ₂ gas are raw material gases for forming the SiN film, and Ar gas is a plasma excitation gas. Hereinafter, this processing gas may be referred to as a “first processing gas”. Further, the first processing gas supply pipe 60 is provided with a supply device group 62 including a valve for controlling the flow of the first processing gas, a flow rate adjusting unit, and the like.

  As shown in FIG. 1, a second processing gas supply pipe 70 as a second processing gas supply unit is provided on the side surface of the processing container 10. A plurality of, for example, 24 second processing gas supply pipes 70 are provided at equal intervals on the circumference of the side surface of the processing container 10. One end of the second processing gas supply pipe 70 is opened on the side surface of the processing container 10, and the other end is connected to the buffer unit 71. The second processing gas supply pipe 70 is disposed obliquely so that one end thereof is positioned below the other end.

The buffer unit 71 is provided in an annular shape inside the side surface of the processing container 10, and is provided in common for the plurality of second processing gas supply pipes 70. A second processing gas supply source 73 is connected to the buffer unit 71 via a supply pipe 72. For example, TSA (trisilylamine), N ₂ gas, H ₂ gas, and Ar gas are individually stored in the second processing gas supply source 63 as processing gases. In the following, this processing gas may be referred to as a “second processing gas”. The supply pipe 72 is provided with a supply device group 74 including a valve for controlling the flow of the second processing gas, a flow rate adjusting unit, and the like.

  The first processing gas from the first processing gas supply pipe 60 is supplied toward the center of the wafer W, and the second processing gas from the second processing gas supply pipe 70 is directed to the outer periphery of the wafer W. Supplied.

  The first processing gas and the second processing gas respectively supplied from the first processing gas supply pipe 60 and the second processing gas supply pipe 70 into the processing container 10 may be the same type of gas. It may be a kind of gas and can be supplied at an independent flow rate or at an arbitrary flow rate ratio.

  Next, plasma processing of the wafer W performed by the plasma processing apparatus 1 configured as described above will be described. In the present embodiment, as described above, the plasma film forming process is performed on the wafer W to form the SiN film on the surface of the wafer W.

  First, the gate valve 12 is opened, and the wafer W is loaded into the processing container 10. The wafer W is mounted on the mounting table 20 by elevating pins. At this time, the DC power supply 23 is turned on, a DC voltage is applied to the electrode 22 of the electrostatic chuck 21, and the wafer W is electrostatically attracted onto the electrostatic chuck 21 by the Coulomb force of the electrostatic chuck 21. Then, after closing the gate valve 12 and sealing the inside of the processing container 10, the exhaust device 33 is operated, and the inside of the processing container 10 is depressurized to a predetermined pressure, for example, 400 mTorr (= 53 Pa).

  Thereafter, the first processing gas is supplied from the first processing gas supply pipe 60 into the processing container 10, and the second processing gas is supplied from the second processing gas supply pipe 70 into the processing container 10. At this time, the flow rate of Ar gas supplied from the first process gas supply pipe 60 is, for example, 100 sccm (mL / min), and the flow rate of Ar gas supplied from the second process gas supply pipe 70 is, for example, 750 sccm ( mL / min).

  Thus, when the first processing gas and the second processing gas are supplied into the processing container 10, the microwave oscillator 55 is operated, and the microwave oscillator 55 has a predetermined power at a frequency of, for example, 2.45 GHz. Generate microwaves. The microwave is radiated into the processing container 10 via the rectangular waveguide 54, the mode converter 53, the coaxial waveguide 50, and the radial line slot antenna 40. The first processing gas and the second processing gas are converted into plasma in the processing chamber 10 by the microwave, and the dissociation of each processing gas proceeds in the plasma. A film forming process is performed on the wafer W by the active species generated at that time. Is made. Thus, a SiN film is formed on the surface of the wafer W.

  While performing the plasma film forming process on the wafer W, the high frequency power supply 25 may be turned on to output a high frequency of a predetermined power at a frequency of 13.56 MHz, for example. This high frequency is applied to the mounting table 20 via the capacitor 24, and an RF bias is applied to the wafer W. In the plasma processing apparatus 1, since the plasma electron temperature can be kept low, there is no damage to the film, and the molecules of the processing gas are easily dissociated by the high-density plasma, thereby promoting the reaction. Further, the application of the RF bias in an appropriate range acts to attract ions in the plasma to the wafer W, so that the denseness of the SiN film is improved and traps in the film are increased.

  Thereafter, when the SiN film is grown and the SiN film having a predetermined thickness is formed on the wafer W, the supply of the first processing gas and the second processing gas and the microwave irradiation are stopped. Thereafter, the wafer W is unloaded from the processing container 10 and a series of plasma film forming processes is completed.

  Next, a specific configuration of the microwave oscillator 55 included in the plasma generation mechanism provided in the plasma processing apparatus 1 having the above-described configuration will be described. FIG. 2 is a block diagram showing a schematic configuration of the microwave oscillator 55 according to the present embodiment.

  As shown in FIG. 2, the microwave oscillator 55 includes a magnetron 100, a power source (so-called magnetron power source) 102, an isolator 104, and an output distribution mechanism 106. The microwave oscillator 55 has a control unit 110 that can control the microwave output distribution ratio in the output distribution mechanism 106. Further, outside the microwave oscillator 55, an external load 120 such as the processing container 10 (including the coaxial waveguide 50, the mode converter 53, and the rectangular waveguide 54) is connected to one output end 106a of the output distribution mechanism 106. And via the waveguide 125. A matching unit 114 having a directional coupler 113 is installed in the waveguide 125, and detectors 116 and 117 are connected to the directional coupler 113. The detector 116 detects traveling wave power, and the detector 117 detects reflected wave (backward wave) power.

  The isolator 104 includes a circulator 104a and a dummy load 104b. The isolator 104 transmits a microwave input from the magnetron 100 to the output distribution mechanism 106 through the waveguide 108, and reflects the microwave (reflected from the output distribution mechanism 106 side). The reflected load) is absorbed by the dummy load 104b. The output distribution mechanism 106 has a configuration for distributing and transmitting the microwaves oscillated from the magnetron 100 through the isolator 104, and one output end 106 a is connected to the micro wave through the waveguide 125 and the matching unit 114. The other output terminal 106 b communicates with the dummy load 122, and communicates with the external load 120 outside the wave oscillator 55.

  The dummy load 104b and the dummy load 122 are configured to incorporate a material that easily absorbs microwaves into the waveguide and to exhaust the material warmed by the microwaves. Specifically, a material that easily absorbs microwaves is called a radio wave absorber, and cooling water circulation, an air cooling fan, or natural cooling is used for exhaust heat. At this time, the voltage standing wave ratio generated by the reflected wave in the dummy loads 104b and 122 is 1.2 or less.

  The magnetron 100 oscillates a microwave as a high frequency according to the voltage supplied from the power source 102. The magnetron 100 is an example of a microwave generator that generates microwaves. Here, the frequency of the microwave oscillated by the magnetron 100 (hereinafter also referred to as an oscillating frequency) is a desired frequency (hereinafter also referred to as a target frequency) that depends on the process processing conditions and the like due to various factors. May vary. Specifically, for example, since the magnetron 100 is a machined product, the oscillation frequency may vary from the target frequency due to a mechanical error between the plurality of magnetrons 100. In addition, since the magnetron 100 has frequency dependency on output power (also referred to as output power or simply output), the oscillation frequency may vary from the target frequency depending on the magnitude of the output power. Furthermore, the oscillation frequency may fluctuate from the target frequency due to aging of the magnetron 100.

  FIG. 3 is an explanatory diagram for explaining the fluctuation of the oscillation frequency due to the output power. In FIG. 3, the horizontal axis indicates the output power (W) of the microwave output from the magnetron 100 detected by the detector 116 from the directional coupler 113, and the vertical axis indicates the oscillation frequency (MHz) of the magnetron 100. ing. As shown in FIG. 3, the oscillation frequency of the magnetron 100 varies within a range of about ± 3 MHz depending on the output power of the magnetron 100. That is, it is shown that the oscillation frequency varies depending on the output power of the magnetron 100 and may vary from the target frequency.

  FIG. 4 is an explanatory diagram of individual differences in the spectrum of microwaves oscillated from the magnetron 100 and dependence on output power. FIG. 4 shows the spectrum of microwaves oscillated when the output powers of three types of magnetrons 100 (magnetrons 1 to 3 in the figure) are 500 W, 1000 W, 3000 W, and 5000 W, respectively. Indicates the spectrum intensity, and the horizontal axis indicates the oscillation frequency. As shown in FIG. 4, the peak of the spectrum of the microwave oscillated from the magnetron 100 is different for each of the three magnetrons 100 (magnetrons 1 to 3), and is also different depending on the output power. That is, it is shown that the spectrum of the microwave oscillated from the magnetron 100 not only has individual differences but also fluctuates every time the output power is changed, and the peak may fluctuate from the target frequency. . FIG. 4 shows that the peak shape of the waveform of the microwave spectrum is more stably observed as the output power increases, and the microwave is oscillated by increasing the output power of the magnetron 100. It can be seen that a microwave having a stable spectrum waveform can be obtained.

FIG. 5 is an explanatory diagram of the temporal variation of the frequency of the microwave oscillated from the magnetron 100. FIG. 5A shows the temporal variation of the frequency with respect to a single output power (3000 W). FIG.5 (b) shows the time-dependent fluctuation | variation of the frequency at the time of changing output power into a several value continuously (1000W-5000W).
As shown in FIG. 5A, it can be seen that the frequency temporarily increases at the start of microwave oscillation (MWON) in the magnetron 100, and thereafter the frequency decreases with time.
Further, as shown in FIG. 5B, when the output power is increased in the magnetron 100, the frequency of the microwave temporarily increases, and thereafter the frequency of the microwave decreases with time at the same output power. Similar behavior occurs when the output power is increased. Although not shown in FIG. 5, when the output power is lowered, the frequency of the microwave temporarily decreases, and thereafter the frequency of the microwave increases with time at the same output power. Become.
That is, in the magnetron 100, even if the microwave is oscillated with the same output power, the frequency fluctuates with time, and the same behavior is obtained when the output power is continuously changed to a plurality of values. I understand that

  Returning to the description of FIG. A power supply 102 shown in FIG. 2 is a power supply that supplies a voltage used for oscillation of microwaves to the magnetron 100, and is configured by, for example, an anode power supply and a filament power supply.

  The output distribution mechanism 106 is a so-called power splitter, and distributes the microwave output transmitted from the magnetron 100 through the waveguide 108 to one output end 106a and the other output end 106b. Device. The microwave output from the output end 106a is transmitted to the external load 120 via the waveguide 125 and the matching unit 114, and is used for plasma processing gas in the processing container 10. On the other hand, the microwave output from the output end 106 b is configured to be absorbed by the dummy load 122. As an example, a microwave oscillated with an output power of 5000 W in the magnetron 100 is transmitted to the output distribution mechanism 106, and then transmitted from the output end 106a to the external load 120 as a microwave with an output power of 3000 W, and from the output end 106b. The microwave with an output power of 2000 W is sent to the dummy load 122 and absorbed.

  FIG. 6 is a schematic explanatory diagram illustrating an example of the configuration of the output distribution mechanism 106. As shown in FIG. 6, the output distribution mechanism 106 is provided with one input end 130 and two output ends 106a and 106b. Further, in the output distribution mechanism 106, the first adjustment unit 133 for adjusting the distribution ratio (output distribution ratio) of the input microwave is on the output end 106a side, and the second adjustment unit 134 is on the output end 106b side. Is provided. The input end 130 and the output ends 106a and 106b are configured by communicating waveguides. The first adjusting unit 133 is provided with a movable member 133a that reflects the propagating microwave, and the second adjusting unit 134 is provided with a movable member 134a that reflects the propagating microwave.

  As shown in FIG. 6, when the in-tube wavelength of the microwave input from the input end 130 is λg, the distance between the first adjusting unit 133 inlet and the second adjusting unit 134 inlet is λg / 2. The microwave input from the input end 130 is propagated between the first adjustment unit 133 and the second adjustment unit 134. Here, as an example, as shown in the figure, for example, the movable member 133 a is arranged so that the microwave does not propagate inside the first adjustment unit 133, and the microwave propagates inside the second adjustment unit 134. A case will be described in which the movable member 134a is arranged so as to secure the distance by λg / 4. The output side in which an odd multiple of λg / 4 is secured is in an open state (open), and the output side in which an even multiple of λg / 4 is secured is in a short (short-circuit) state. Is known to propagate. That is, in the case shown in the figure, the microwave propagates only to the output end 106a and does not propagate to the output end 106b.

The output distribution mechanism 106 can arbitrarily adjust the ratio of the microwaves propagated to the output end 106a and the output end 106b by appropriately arranging the movable members 133a and 134a in the configuration described above. Is. FIG. 7 is a graph showing the relationship between the positions of the movable members 133a and 134a in the output distribution mechanism 106 configured as described above and the distribution ratio of the microwaves propagated to the output end 106a and the output end 106b. FIG. 7 shows a case where one movable member (for example, movable member 133a) is moved from the reference point (0 mm) to 80 mm as an example.

As shown in FIG. 7, in the output distribution mechanism 106, by moving the movable members 133a and 134a, the ratio of the microwaves propagated to the output end 106a and the output end 106b (that is, the output distribution ratio) is an arbitrary value. Can be adjusted.

Returning to the description of FIG. The microwave oscillator 55 is provided with a control unit 110 that controls a microwave output distribution ratio in the output distribution mechanism 106. As indicated by the alternate long and short dash line in FIG. 2, based on the microwave traveling wave power signal detected by the detector 116, the control unit 110 determines an optimal output distribution ratio and performs control. That is, for example, when process processing is performed in the external load 120, the microwave having a predetermined output power set according to the process condition is detected with the output distribution ratio such that the detector 116 detects the microwave. An output distribution ratio is determined.
Process processing in a generally known plasma processing apparatus is set to use microwaves having an output power of 500 W to 5000 W or less, and therefore, the output power of 500 W to 5000 W or less is applied to the external load 120 from the microwave oscillator 55. The output distribution ratio is controlled such that the microwaves are propagated.

  Below, the specific flow of control of the output power of a microwave is demonstrated using the microwave oscillator 55 comprised as shown in FIG.

  First, the output power of the magnetron 100 is output constantly. However, the output power at this time is set to be equal to or higher than the output power of the microwave used in the external load 120, and is preferably set to, for example, 3000 W or higher where the spectrum waveform is stable.

  Next, when the output of the magnetron 100 is started, the distribution ratio is set such that all the microwaves are output to the output terminal 106b by the output distribution mechanism 106 (that is, the output terminal 106a: output terminal 106b = 0: 100), and the dummy load 122 absorbs the output of all microwaves.

  Then, the state in which all the microwave outputs are absorbed by the dummy load 122 is continued until the spectrum waveform of the microwaves is stabilized. For example, the spectrum shape of the microwave is stabilized in about 30 seconds. The plasma processing apparatus may be activated, the condition in the processing container may be adjusted, the object to be processed (wafer W) may be transferred using the time required for stabilizing the microwave spectrum waveform. As a result, the wafer W can be processed without reducing the throughput.

  Subsequently, the microwave output power required in the external load 120 is set, and the distribution ratio of the output distribution mechanism 106 is controlled based on the power signal from the detector 116 to obtain a predetermined distribution ratio. For example, when a predetermined plasma processing process is performed in the external load 120, the distribution ratio controlled in this way is maintained for a predetermined process time.

  Here, when the recipe of the plasma processing process in the external load 120 is different, a microwave with an output power different from that in the previous process may be required. In this case, the output power of the microwave propagated to the external load 120 is changed by changing the output distribution ratio of the microwave in the output distribution mechanism 106 so that the power signal detected by the detector 116 becomes a further predetermined value. Control.

  Finally, when the microwave oscillation is stopped due to the end of the plasma processing process or the like, the output distribution ratio in the output distribution mechanism 106 is set so that all the microwaves are output to the output end 106b as in the output start. A reasonable distribution ratio. Thereby, all the microwave outputs are absorbed by the dummy load 122.

  As described above, according to the plasma processing apparatus 1 according to the present embodiment, in particular, the microwave oscillator 55, the output of the microwave oscillated from the magnetron 100 is distributed by the output distribution mechanism 106 and distributed. Of the output power is propagated to the external load 120. At this time, the spectrum waveform of the microwave of the predetermined output power to be distributed is stabilized regardless of the output power of the magnetron 100, and is a substantially constant waveform regardless of the distribution ratio of the output distribution mechanism 106. Also, the frequency of the distributed microwave is almost a predetermined frequency (that is, the target frequency) regardless of the distribution ratio of the output distribution mechanism 106. Therefore, the microwave frequency used when performing the process in the plasma processing apparatus 1 can be stably set to a desired target frequency, and the spectrum waveform of the microwave can be stably set to a desired shape. it can.

  In particular, the output distribution mechanism 106 does not change the output power of the microwave oscillated from the magnetron 100 even when the plasma processing apparatus 1 starts the process processing or changes the processing conditions when performing a plurality of process processing continuously. Since the output is adjusted by changing the distribution ratio, a microwave having a desired target frequency and spectrum shape can be stably used. For this reason, stabilization of the process conditions in the plasma processing apparatus 1 is achieved.

  In addition, when a plurality of process processes are continuously performed, it is not necessary to frequently switch between oscillation and non-oscillation of the microwave in the magnetron 100, and thermal stress inside the magnetron can be alleviated to extend the life. it can.

  FIG. 8 illustrates a comparison between a microwave spectrum waveform (conventional example) oscillated from a conventional magnetron and a microwave spectrum waveform (example of the present invention) distributed by the output distribution mechanism 106 according to the present embodiment. FIG. In FIG. 8, the vertical axis represents intensity dB, the horizontal axis represents frequency MHz, and the spectrum waveforms when the output power is 500 W, 1000 W, 3000 W, and 5000 W are shown.

  As shown in FIG. 8, the spectrum spectrum of the microwave of the conventional example has a remarkable variation depending on the output power, and the peak of the frequency in the spectrum also varies with each output power. On the other hand, the spectrum spectrum of the microwave according to the present invention has a substantially constant shape regardless of the output power, and the frequency peaks in the spectrum show substantially the same peak regardless of the output power. That is, it can be seen that by using the configuration using the output distribution mechanism 106 according to the present embodiment, it is possible to obtain a microwave having a constant spectrum waveform whose frequency is a desired target frequency and with little variation.

  Further, as described above with reference to FIG. 4, as a characteristic of the magnetron 100, the spectrum waveform of the microwave oscillated with low output power has a variation in peak shape and is often an unstable shape. It is known that the influence of individual differences is also remarkable. In this regard, according to the microwave oscillator 55 according to the present embodiment, the output power of the microwave oscillated from the magnetron 100 is set to a high output power with a stable spectrum waveform and the like, and the output distribution by the output distribution mechanism 106 is performed. By controlling the ratio, a microwave with low output power can be obtained. That is, even when a microwave with a low output power of, for example, 500 W or less is required in the process processing, the process processing can be performed using a microwave with a constant spectrum waveform.

  As mentioned above, although an example of embodiment of this invention was demonstrated, this invention is not limited to the form of illustration. It is obvious for those skilled in the art that various modifications or modifications can be conceived within the scope of the idea described in the claims, and these naturally belong to the technical scope of the present invention. It is understood.

(Another embodiment of the present invention)
In the above-described embodiment, as the control of the output distribution mechanism 106 by the control unit 110, the control unit 110 determines the optimal output distribution ratio based on the microwave traveling wave power signal detected by the detector 116. However, the present invention is not limited to this. For example, the voltage supplied by the power source 102 may be controlled based on the output distribution ratio of the microwave in the output distribution mechanism 106 and the power signal detected by the detector 116.

  FIG. 9 is a block diagram showing a schematic configuration of a microwave oscillator 55 according to another embodiment of the present invention. In FIG. 9, components having the same functional configuration as those of the above embodiment are denoted by the same reference numerals and description thereof is omitted. As shown in FIG. 9, in this configuration, the voltage supplied by the power source 102 is controlled by the control unit 110, and as a result, the output power of the magnetron 100 is controlled.

  In the microwave oscillator 55, the output power of the microwave oscillated from the magnetron 100 is distributed with a predetermined distribution ratio by the output distribution mechanism 106 and propagated to the external load 120, and is oscillated from the magnetron 100. The output power of the microwave is required to be equal to or higher than the output power of the microwave required under the process processing conditions at the external load 120. For this reason, for example, when a plurality of process processes are continuously performed in the external load 120, the required microwave output power may change. In such a case, as described in the above embodiment, it can be dealt with by changing the output distribution ratio in the output distribution mechanism 106, but the output power of the microwave required in the external load 120 is magnetron. If the output power exceeds the output power of the microwave oscillated from 100, it cannot be dealt with only by changing the output distribution ratio in the output distribution mechanism 106. Therefore, in such a case, the power supply 102 is controlled by the configuration shown in FIG. 9 so that the output power of the microwave oscillated from the magnetron 100 is equal to or higher than the output power of the microwave required by the external load 120. Thus, it is possible to suitably perform the process processing with the external load 120.

(First modification of the present invention)
In addition to the configuration described in the above embodiment, a voltage control mechanism for controlling the voltage supplied from the power source 102 to the magnetron 100 may be provided. FIG. 10 is a block diagram showing a schematic configuration of the microwave oscillator 55 according to the first modification of the present invention. In FIG. 10, components having the same functional configuration as those of the above embodiment are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 10, in this modification, a voltage control mechanism 150 is provided between the power source 102 and the magnetron 100, and the voltage control mechanism 150 is supplied to the magnetron 100 based on an electronic signal from the detector 116. The voltage to be controlled is controlled. As described in the above embodiment, the detector 116 corresponds to a traveling wave power measurement mechanism that detects a traveling wave of the microwave supplied to the external load 120, and the detector 117 is a microwave supplied to the external load 120. This corresponds to a reflected wave power measuring mechanism that detects the reflected wave of the.

  In such a configuration, a voltage corresponding to the power obtained by adding the traveling wave power detected by the detector 116 to the power calculated based on the reflected wave power detected by the detector 117 is supplied to the magnetron 100. Such so-called load control can be performed. As a result, with respect to the microwave oscillated from the magnetron 100, it is possible to reduce the risk of mode jump of the generated standing wave mode to a lower mode, and a stable mode can be obtained in a short time. In addition, the influence of the reflected wave on the effective load power, which is the power supplied to the external load 120 side, can be greatly reduced, and stable plasma process processing can be performed more reliably in the external load 120.

(Second modification of the present invention)
In addition to the configuration described in the above embodiment, an impedance generator, a frequency coupler, a frequency are used as adjustment units for adjusting the oscillation frequency of the microwave oscillated from the magnetron 100 in the microwave oscillator 55 to a predetermined frequency. A detector and an oscillation frequency adjuster may be provided. FIG. 11 is a block diagram showing a schematic configuration of a microwave oscillator 55 according to a second modification of the present invention. In FIG. 11, components having the same functional configuration as those of the above embodiment are given the same reference numerals and description thereof is omitted.

  As shown in FIG. 11, in this modification, an impedance generator 160 is provided on the rear side of the magnetron 100 in the waveguide 108 to generate an impedance applied to the magnetron 100. Further, a frequency coupler 161 is connected to the output end side of the impedance generator 160 to branch the microwave traveling from the impedance generator 160 to the external load 120 side, and the branched microwave is separated from the isolator 104 and the frequency detector 162. Output to.

  The frequency detector 162 detects the oscillation frequency adjusted to the target frequency by the oscillation frequency adjuster 163. The oscillation frequency adjuster 163 obtains a difference between the oscillation frequency input from the frequency detector 162 and the target frequency, sets the impedance generator 160 so as to reduce the difference, and sets the oscillation frequency to the target frequency. To be adjusted.

  In such a configuration, by setting the impedance generator 160 appropriately, it is possible to stably control the oscillation frequency of the microwave oscillated from the magnetron 100 to a constant target frequency. As described with reference to FIGS. 3 and 4 in the above embodiment, the oscillation frequency of the microwave oscillated from the magnetron 100 varies according to the output power, and there is an individual difference in the magnetron 100. In some cases, the target frequency may fluctuate. It is possible to keep the target frequency constant by suppressing such transient fluctuation elements according to the output power of the microwave oscillated from the magnetron 100, frequency fluctuations due to individual differences of the magnetron 100, and the like.

  In the above-described embodiment, as an example of the process processing in the plasma processing apparatus 1, the surface of the wafer W as the object to be processed is subjected to plasma CVD processing, and a SiN film (silicon nitride film) is formed on the surface of the wafer W. However, the scope of application of the present invention is not limited to this. In other words, the present invention can be applied to any technique in which plasma processing is performed on an object to be processed by exciting a plasma in a processing container using a microwave oscillator. For example, for a film formed on a wafer W Of course, the present invention can also be applied to a technique for performing an etching process.

  Further, in the plasma processing apparatus 1 according to the above-described embodiment, the configuration in which the radial line slot antenna 40 is provided on the ceiling surface of the processing container 10 has been described. However, the antenna configuration of the plasma processing apparatus is limited to this. Instead, the present invention is applicable to plasma processing apparatuses having various configurations. However, a processing apparatus configured to perform plasma processing using microwaves via a radial line slot antenna is sensitive to the frequency characteristics and spectrum characteristics of the propagated microwave because the antenna has frequency characteristics. Therefore, the present invention is particularly useful for a plasma processing apparatus configured to perform plasma processing using microwaves via a radial line slot antenna.

  The present invention can be applied to a plasma processing apparatus and a plasma processing method.

DESCRIPTION OF SYMBOLS 1 Plasma processing apparatus 10 Processing container 11 Carry-in / out opening 12 Gate valve 20 Mounting stand 32 Exhaust pipe 40 Radial line slot antenna 50 Coaxial waveguide 55 Microwave oscillator 60 1st process gas supply pipe 70 2nd process gas supply pipe 100 Magnetron 106 Output distribution mechanism 120 External load 150 Voltage control mechanism 160 Impedance generator W Wafer

Claims (10)

A plasma processing apparatus for processing an object to be processed,
A processing container for accommodating a target object and performing plasma processing;
Including a microwave oscillator, comprising a plasma generation mechanism for generating plasma in the processing container using a microwave oscillated by the microwave oscillator;
The microwave oscillator distributes the output of the microwave oscillated from the microwave oscillator, one as an output for generating plasma in the processing container and the other as an output to be absorbed by a dummy load provided outside the processing container. An output distribution mechanism to
And a control unit that controls an output distribution ratio of microwaves in the output distribution mechanism. A matching unit including a directional coupler is provided between the output distribution mechanism and the processing container,
The directional coupler is provided with a detector that detects a power signal of a traveling wave of microwaves distributed to generate plasma in the processing container in the output distribution mechanism,
The plasma processing apparatus according to claim 1, wherein the control unit controls an output distribution ratio of microwaves in the output distribution mechanism based on a power signal detected by the detector. A power source for supplying a voltage to the microwave oscillator is provided;
The control unit controls a voltage supplied to the microwave oscillator based on an output distribution ratio of a microwave in the output distribution mechanism and a power signal detected by the detector. The plasma processing apparatus according to 1. The plasma generation mechanism includes a dielectric window that transmits the microwave generated by the microwave oscillator into the processing container;
The plasma processing apparatus according to claim 1, further comprising a slot antenna plate that is provided with a plurality of slots and that radiates the microwaves to the dielectric window. 5. The plasma processing apparatus according to claim 1, wherein an output of a microwave oscillated from the microwave oscillator is 500 W or more and 5000 W or less. The plasma processing apparatus according to claim 1, wherein the microwave oscillator includes a magnetron. A plasma processing apparatus comprising: a processing container that performs plasma processing inside; and a plasma generation mechanism that includes a microwave oscillator and generates plasma in the processing container using microwaves oscillated by the microwave oscillator. A plasma processing method for processing an object to be processed,
The output of the microwave oscillated from the microwave oscillator, one is output by generating plasma in the processing container, the other is distributed by an output distribution mechanism as an output to be absorbed by a dummy load provided outside the processing container,
A plasma processing method for performing plasma processing by generating plasma in the processing container using the distributed microwave of one output. The processing of the object to be processed includes a plurality of continuous plasma processing steps,
The plurality of plasma processing steps are performed by generating plasma in the processing container using microwaves having different predetermined outputs,
The microwave output oscillated from the microwave oscillator is constant,
By controlling the microwave output distribution ratio in the output distribution mechanism, the microwave output for generating plasma in the plurality of successive plasma processing steps is continuously changed to a predetermined value for each step. The plasma processing method according to claim 7, wherein: The plasma processing method according to claim 7 or 8, wherein the output of the microwave oscillated from the microwave oscillator is more than 500W and not more than 5000W. The plasma processing method according to claim 7, wherein the microwave oscillator includes a magnetron.

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