Plasma processing apparatus and plasma processing method

Abstract

The invention provides a plasma processing apparatus. The plasma processing apparatus comprises a plasma processing chamber; the antenna is arranged at the upper part of the plasma processing chamber or above the plasma processing chamber; the RF power supply is electrically connected with the antenna and can control the frequency of output electric power; and a control unit capable of outputting a first output electric power having a first frequency and a second output electric power having a second frequency, the second output electric power being lower than the output electric power having the first frequency, the control unit being capable of performing: a step (a) of scanning the second frequency, searching for and determining a resonance point; and (b) tuning the first frequency to the resonance point.

Description

Technical Field

[0001] The present invention relates to a plasma processing device and a plasma processing method. Background Art

[0002] Patent document 1 discloses a technology for igniting plasma in a plasma processing device. The plasma processing device includes an electric power supply unit and a frequency control unit. Patent document 1 discloses that when the frequency control unit generates plasma of a processing gas in a processing container, the frequency of the electric power supplied by the electric power supply unit to the processing container is swept from a first frequency to a second frequency.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2020-71912 Summary of the invention

[0006] Technical problem to be solved by the invention

[0007] The technology of the present invention can efficiently generate or maintain plasma in an inductively coupled plasma processing apparatus.

[0008] Means for solving technical problems

[0009] One embodiment of the present invention provides a plasma processing device, characterized in that it includes: a plasma processing chamber; an antenna, which is arranged on the upper part of the plasma processing chamber; an RF power supply, which is electrically connected to the antenna and can control the frequency of the output electric power; and a control unit, wherein the RF power supply can output a first output electric power with a first frequency and a second output electric power with a second frequency, and the second output electric power is smaller than the output electric power with the first frequency, and the control unit can perform: step (a), scanning the second frequency, searching for and determining a resonance point; and step (b), tuning the first frequency to the resonance point.

[0010] Effects of the Invention

[0011] According to the present invention, plasma can be efficiently generated or maintained in an inductively coupled plasma processing apparatus. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is an explanatory diagram showing a configuration example of a plasma processing system according to an embodiment.

[0013] Figure 2 It is a cross-sectional view showing a structural example of a plasma processing apparatus according to one embodiment.

[0014] Figure 3 It is an explanatory diagram showing a structural example of a plasma processing apparatus according to an embodiment.

[0015] Figure 4 1 is a flowchart showing an example of a plasma processing method according to an embodiment.

[0016] Figure 5 This is an explanatory diagram for explaining the state and control cycle of plasma in a plasma processing method according to one embodiment.

[0017] Fig. 6A This is an explanatory diagram for explaining the details and significance of a plasma processing method according to one embodiment.

[0018] Figure 6B This is an explanatory diagram for explaining the details and significance of a plasma processing method according to one embodiment.

[0019] Figure 6C This is an explanatory diagram for explaining the details and significance of a plasma processing method according to one embodiment.

[0020] Fig. 7A This is an explanatory diagram for explaining the details and significance of a plasma processing method according to one embodiment.

[0021] Figure 7B This is an explanatory diagram for explaining the details and significance of a plasma processing method according to one embodiment.

[0022] Figure 7C This is an explanatory diagram for explaining the details and significance of a plasma processing method according to one embodiment.

[0023] Figure 8 1 is a flowchart showing an example of a plasma processing method according to an embodiment.

[0024] Fig. 9A This is an explanatory diagram for explaining the details and significance of a plasma processing method according to one embodiment.

[0025] Fig. 9B This is an explanatory diagram for explaining the details and significance of a plasma processing method according to one embodiment.

[0026] Fig. 9C This is an explanatory diagram for explaining the details and significance of a plasma processing method according to one embodiment.

[0027] Fig.9DThis is an explanatory diagram for explaining the details and significance of a plasma processing method according to one embodiment.

[0028] Fig.9E This is an explanatory diagram for explaining the details and significance of a plasma processing method according to one embodiment.

[0029] Fig.9F This is an explanatory diagram for explaining the details and significance of a plasma processing method according to one embodiment.

[0030] Figure 9G This is an explanatory diagram for explaining the details and significance of a plasma processing method according to one embodiment.

[0031] Fig. 10A This is an explanatory diagram for explaining the details and significance of a plasma processing method according to one embodiment.

[0032] Fig. 10B This is an explanatory diagram for explaining the details and significance of a plasma processing method according to one embodiment.

[0033] Fig. 10C This is an explanatory diagram for explaining the details and significance of a plasma processing method according to one embodiment.

[0034] Fig. 10D This is an explanatory diagram for explaining the details and significance of a plasma processing method according to one embodiment.

[0035] Fig.10E This is an explanatory diagram for explaining the details and significance of a plasma processing method according to one embodiment.

[0036] Fig.10F This is an explanatory diagram for explaining the details and significance of a plasma processing method according to one embodiment.

[0037] Fig.11A It is an explanatory diagram for explaining a plasma processing method according to a comparative example.

[0038] Fig. 11B It is an explanatory diagram for explaining a plasma processing method according to a comparative example.

[0039] Fig. 11C It is an explanatory diagram for explaining a plasma processing method according to a comparative example. DETAILED DESCRIPTION

[0040] In the manufacturing process of semiconductor devices, a semiconductor substrate (hereinafter referred to as "substrate") is subjected to plasma processing such as etching and film formation. In the plasma processing, a processing gas is excited to generate plasma, and the wafer is processed using the plasma.

[0041] Plasma processing requires high processing rate, high fineness, and high depth processing, and in order to achieve this processing, a processing method using high-density plasma has been put into practical use.

[0042] In order to generate high-density plasma, for example, an inductively coupled (ICP) plasma processing apparatus (etching processing apparatus) using an induction coil can be used. A resonant circuit is formed by the inductance component of the induction coil and the capacitance component of the plasma. By tuning the frequency of the electric power output from the source RF power supply to the resonant point of the resonant circuit, the impedance between the source RF power supply and the plasma is matched, and plasma with high electric power efficiency can be generated. On the other hand, the resonant circuit of the ICP plasma processing apparatus has a high Q characteristic (Quality-factor characteristic) and has a narrow frequency width (resonance width) of impedance matching.

[0043] Next, use Figures 11A to 11C An impedance matching control method according to a comparative example will be described. Figures 11A to 11C Impedance matching control of plasma by frequency control of a source RF power source (hereinafter, sometimes simply referred to as “matching control”) is shown as a comparative example.

[0044] exist Fig.11A In the matching control of the comparative example, each figure shows the impedance between the source RF power supply and the plasma, the source RF electric power output from the source RF power supply (output electric power), and the electric power supplied to the plasma (supply electric power) from the top. In each figure, the horizontal axis is the value of the frequency. In the impedance figure, the vertical axis is the value of the impedance. In the output electric power and supply electric power figures, the vertical axis is the value of the electric power. The frequency of the output electric power before scanning is F(1). In addition, the resonance point of the impedance includes the first resonance point FP 1 and the second resonance point FP 2 , the anti-resonance point includes the first anti-resonance point RP 1 and the second anti-resonance point RP 2 .

[0045] The power supplied to the plasma is obtained by integrating the output power of each frequency absorbed by the plasma among the output power outputted by the source RF power source. 1When the impedance is not matched, a part of the output power is not absorbed by the plasma and becomes a loss. Therefore, in the matching control, it is required to tune the frequency F of the output power to the first resonance point FP. 1 To achieve impedance matching, thereby supplying output electrical power to the plasma with minimal loss.

[0046] In addition, it is also important to supply enough power to maintain the plasma. 1 To the first anti-resonance point RP 1 When the impedance changes, the impedance increases sharply. The increase in impedance becomes the cause of the reduction of the power supplied to the plasma. When the power supplied is lower than a certain level, the plasma cannot be maintained. Therefore, it is required to prevent the frequency F of the output power from decreasing to the first anti-resonance point RP. 1 The sharp increase in impedance caused by side movement.

[0047] Fig. 11B In the matching control of the comparative example, the power output from the source RF power source is swept from the frequency F(1) to the first resonance point FP 1 The control step of tuning the frequency F(2). In one control cycle, when the frequency F of the electric power output from the source RF power source is equal to the first resonance point FP 1 During tuning, impedance matching occurs, and the power supplied to the plasma is maximized. In this control cycle, the scan is terminated when the power supplied to the plasma is maximized. After the scan is completed, the following control is performed: the power supplied to the plasma is monitored, and the frequency F of the output power is periodically adjusted so that the power supplied is always maximized. As an example, when the power supplied is below the desired threshold, the next control cycle is entered, and the scan is performed again. Here, the impedance of the plasma is not always constant, and may change due to changes in the power supplied, the pressure in the plasma space, the gas mixing ratio, etc.

[0048] Fig. 11C This shows that in the matching control of the comparative example, due to the change of plasma, the resonance point of the impedance changes from the first resonance point FP 1 Transfer to the second resonance point FP 2 In this state, the first resonance point FP 1 The frequency F(2) of the tuned output power is not at the second resonance point FP 2 Tuning reduces the degree of impedance matching and reduces the electrical power supplied to the plasma.

[0049] As mentioned above for Figures 11A to 11CAs described above, in the comparative example, matching control is performed by frequency control of a single output power. Specifically, by frequency sweeping of the output power of the source RF power supply for maintaining plasma, the resonance point search and determination and tuning control are performed simultaneously. In the search for the resonance point, the frequency of the output power is moved to the resonance point before and after the resonance point, and then the frequency at which the supplied power becomes the maximum is searched. Therefore, in its operation, there is inevitably a case where the frequency moves from the resonance point side to the anti-resonance point side.

[0050] The present inventors have conducted in-depth research on the matching control of the comparative example and found the following. That is, when the anti-resonance point moves toward the frequency F of the output power due to the change of impedance, the impedance increases sharply. In particular, in the case of a high-Q resonance characteristic, the change is more significant. Fig. 11C As shown, even if the frequency F of the output electric power is increased from the second resonance point FP 2 To the second anti-resonance point RP 2 Therefore, there is the following technical problem: due to the control action of the frequency F of the output power moving from the resonance point side to the anti-resonance point side, or the action of the resonance point moving, the power supply to the plasma is easily reduced.

[0051] In addition, the following is also known. That is, there is a technical problem that overcontrol is easily caused by measurement errors of various sensors or measuring instruments in matching control, control amount or control error of frequency during search, or changes in pressure or gas conditions inside the chamber. Due to overcontrol, there is a technical problem that plasma may be extinguished due to the frequency of output electric power shifting to the anti-resonance point side by an unexpected amount during matching control.

[0052] In addition, in the processing of substrate processing, in the past, before changing the chamber conditions such as pressure fluctuation, gas mixing ratio or flow rate, a static method of temporarily stopping the supply of output electric power from the source RF power supply to extinguish the plasma was performed. In the static method, after the plasma was extinguished, after the setting in the chamber corresponding to the chamber conditions was completed, the output electric power from the source RF power supply was restarted to re-ignite the plasma. However, in recent years, in order to perform more complex processing, a dynamic method of continuously changing the chamber conditions while maintaining the plasma is required.

[0053] The inventors of the present invention have conducted in-depth research on the processing of substrate processing in the comparative example, and found the following: That is, compared with the static method, the dynamic method described above is accompanied by greater impedance fluctuations when the conditions in the chamber are changed, and therefore, there is a technical problem that it is difficult to stably match the impedance in the matching control of the comparative example.

[0054] In view of the above-mentioned technical problems, the present invention provides a plasma processing method capable of performing impedance matching control to further improve stability.

[0055] Hereinafter, the structure of the substrate processing apparatus of this embodiment will be described with reference to the drawings. In addition, in this specification, for elements having substantially the same functional configuration, the same reference numerals are given to omit repeated description.

[0056] <Plasma treatment system>

[0057] Figure 1 : is a diagram for illustrating a structural example of a plasma processing system. In one embodiment, the plasma processing system includes a plasma processing device 1 and a control unit 2. The plasma processing system is an example of a substrate processing system, and the plasma processing device 1 is an example of a substrate processing device. The plasma processing device 1 includes a plasma processing chamber 10, a substrate support portion 11, and a plasma generating portion 12. The plasma processing chamber 10 has a plasma processing space. In addition, the plasma processing chamber 10 has: at least one gas supply port for supplying at least one processing gas to the plasma processing space; and at least one gas exhaust port for exhausting gas from the plasma processing space. The gas supply port is connected to the gas supply portion 20 described later, and the gas exhaust port is connected to the exhaust system 40 described later. The substrate support portion 11 is arranged in the plasma processing space and has a substrate supporting surface for supporting a substrate.

[0058] The plasma generating unit 12 is capable of generating plasma from at least one processing gas supplied into the plasma processing space. The plasma formed in the plasma processing space may be a capacitively coupled plasma (CCP: Capacitively Coupled Plasma), an inductively coupled plasma (ICP: Inductively Coupled Plasma), an ECR plasma (Electron-Cyclotron-resonance Plasma: Electron Cyclotron Resonance Plasma), a helicon wave excited plasma (HWP: Helicon Wave Plasma) or a surface wave plasma (SWP: Surface Wave Plasma), etc. In addition, various types of plasma generating units including an AC (Alternating Current: Alternating Current) plasma generating unit and a DC (Direct Current: Direct Current) plasma generating unit may also be used. In one embodiment, the AC signal (AC electric power) used in the AC plasma generating unit has a frequency in the range of 100kHz to 10GHz. Therefore, the AC signal includes an RF (Radio Frequency: Radio Frequency) signal and a microwave signal. In one embodiment, the RF signal has a frequency in the range of 100kHz to 150MHz.

[0059] The control unit 2 is capable of processing computer-executable commands, which are used to cause the plasma processing device 1 to perform the various steps described in the present invention. The control unit 2 is capable of controlling the various elements of the plasma processing device 1 to perform the various steps described herein. In one embodiment, part or all of the control unit 2 may be included in the plasma processing device 1. The control unit 2 may include a processing unit 2a1, a storage unit 2a2, and a communication interface 2a3. The control unit 2 is implemented, for example, by a computer 2a. The processing unit 2a1 is capable of reading a program from the storage unit 2a2 and performing various control actions by executing the read program. The program may be pre-stored in the storage unit 2a2 or acquired via a medium when necessary. The acquired program is stored in the storage unit 2a2 and read and executed from the storage unit 2a2 by the processing unit 2a1. The medium may be various storage media readable by the computer 2a, or a communication line connected to the communication interface 2a3. The processing unit 2a1 may be a CPU (Central Processing Unit). The storage unit 2a2 may include a RAM (Random Access Memory), a ROM (Read Only Memory), a HDD (Hard Disk Drive), an SSD (Solid State Drive), or a combination thereof. The communication interface 2a3 may communicate with the plasma processing apparatus 1 via a communication line such as a LAN (Local Area Network). The control unit 2 may include an RF control unit 70 described later.

[0060] <Plasma processing equipment>

[0061] Next, a configuration example of an inductively coupled plasma processing apparatus 1 will be described as an example of the plasma processing apparatus 1 . Figure 2 This is a diagram for explaining a configuration example of an inductively coupled plasma processing apparatus 1 .

[0062] The inductively coupled plasma processing apparatus 1 includes a plasma processing chamber 10, a gas supply unit 20, a power supply 30, and an exhaust system 40. The plasma processing chamber 10 includes a dielectric window 101. In addition, the plasma processing apparatus 1 includes a substrate support unit 11, a gas introduction unit, and an antenna 14. The substrate support unit 11 is disposed in the plasma processing chamber 10. The antenna 14 is disposed on or above the plasma processing chamber 10 (i.e., on or above the dielectric window 101). The plasma processing chamber 10 has a plasma processing space 10s defined by the dielectric window 101, the side wall 102 of the plasma processing chamber 10, and the substrate support unit 11. The plasma processing chamber 10 is grounded.

[0063] The substrate support portion 11 includes a main body 111 and a ring assembly 112. The main body 111 has: a central area 111a for supporting a substrate W; and an annular area 111b for supporting the ring assembly 112. A wafer is an example of a substrate W. The annular area 111b of the main body 111 surrounds the central area 111a of the main body 111 when viewed from above. The substrate W is arranged on the central area 111a of the main body 111, and the ring assembly 112 is arranged on the annular area 111b of the main body 111 in a manner surrounding the substrate W on the central area 111a of the main body 111. Therefore, the central area 111a is also referred to as a substrate support surface for supporting the substrate W, and the annular area 111b is also referred to as a ring support surface for supporting the ring assembly 112.

[0064] In one embodiment, the main body 111 includes a base 1110 and an electrostatic chuck 1111. The base 1110 includes a conductive component. The conductive component of the base 1110 can function as a bias electrode. The electrostatic chuck 1111 is arranged on the base 1110. The electrostatic chuck 1111 includes a ceramic component 1111a and an electrostatic electrode 1111b arranged in the ceramic component 1111a. The ceramic component 1111a has a central area 111a. In one embodiment, the ceramic component 1111a also has an annular area 111b. In addition, other components surrounding the electrostatic chuck 1111, such as an annular electrostatic chuck or an annular insulating component, may have an annular area 111b. In this case, the ring assembly 112 may be arranged on the annular electrostatic chuck or the annular insulating component, or may be arranged on both the electrostatic chuck 1111 and the annular insulating component. In addition, at least one RF / DC electrode coupled to the RF power supply 31 and / or DC power supply 32 described later may be arranged in the ceramic component 1111a. In this case, at least one RF / DC electrode can function as a bias electrode. In addition, the conductive component of the base 1110 and at least one RF / DC electrode may function as a plurality of bias electrodes. In addition, the electrostatic electrode 1111b may function as a bias electrode. Therefore, the substrate support portion 11 includes at least one bias electrode.

[0065] The ring assembly 112 includes one or more ring-shaped components. In one embodiment, the one or more ring-shaped components include one or more edge rings and at least one cover ring. The edge ring is formed of a conductive material or an insulating material, and the cover ring is formed of an insulating material.

[0066] In addition, the substrate support portion 11 may include a temperature regulating module for regulating at least one of the electrostatic chuck 1111, the ring assembly 112 and the substrate W to a target temperature. The temperature regulating module may include a heater, a heat transfer medium, a flow path 1110a or a combination thereof. A heat transfer fluid such as salt water or gas may flow in the flow path 1110a. In one embodiment, the flow path 1110a is formed in the base 1110, and one or more heaters are arranged in the ceramic part 1111a of the electrostatic chuck 1111. In addition, the substrate support portion 11 may include a heat transfer gas supply portion for supplying a heat transfer gas to the gap between the back side of the substrate W and the central area 111a.

[0067] The gas introduction part can introduce at least one processing gas from the gas supply part 20 into the plasma processing space 10s. In one embodiment, the gas introduction part includes a central gas injection part (CGI: Center Gas Injector) 13. The central gas injection part 13 is arranged above the substrate support part 11 and is installed in the central opening part formed in the dielectric window 101. The central gas injection part 13 has at least one gas supply port 13a, at least one gas flow path 13b and at least one gas introduction port 13c. The processing gas supplied to the gas supply port 13a can be introduced into the plasma processing space 10s from the gas introduction port 13c through the gas flow path 13b. In addition, the gas introduction part may include one or more side gas injection parts (SGI: Side Gas Injector) installed in one or more openings formed on the side wall 102 in addition to the central gas injection part 13 or instead of the central gas injection part 13.

[0068] The gas supply unit 20 may include at least one gas source 21 and at least one flow controller 22. In one embodiment, the gas supply unit 20 is capable of supplying at least one processing gas from the gas source 21 corresponding to each other via the flow controller 22 corresponding to each other to the gas introduction unit. Each flow controller 22 may include, for example, a mass flow controller or a pressure-controlled flow controller. Moreover, the gas supply unit 20 may include at least one flow modulation device for modulating or pulsing the flow of at least one processing gas. Thus, the gas pressure and mixing ratio in the plasma processing space 10s can be adjusted to a desired value.

[0069] The power supply 30 includes an RF power supply 31 coupled to the plasma processing chamber 10 via at least one impedance matching circuit. The RF power supply 31 is capable of supplying at least one RF signal (RF electric power) to at least one bias electrode and the antenna 14. Thereby, a plasma can be formed from at least one processing gas supplied to the plasma processing space 10s. Therefore, the RF power supply 31 can function as at least a part of the plasma generation unit 12. In addition, by supplying a bias RF signal to at least one bias electrode, a bias potential can be generated on the substrate W, and ions in the formed plasma can be attracted to the substrate W.

[0070] In one embodiment, the RF power supply 31 includes a source RF power supply 31a and a bias RF power supply 31b. The source RF power supply 31a is coupled to the antenna 14 via at least one impedance matching circuit, and is capable of generating a source RF signal (source RF electric power) for plasma generation and outputting it to the antenna 14. In one embodiment, the source RF signal has a frequency in the range of 10 MHz to 150 MHz. The source RF power supply 31a is capable of generating a plurality of source RF signals having different frequencies described later and outputting them to the antenna 14. In one embodiment, the source RF power supply 31a is a variable frequency power supply. The plurality of output source RF signals (hereinafter referred to as output electric power) are supplied to the antenna 14. A part of the output electric power supplied to the antenna 14 is reflected and does not contribute to the generation or maintenance of the plasma. Such electric power is referred to as reflected electric power. In addition, the electric power that contributes to the generation or maintenance of the plasma is referred to as supplied electric power. The details of the output electric power, the reflected electric power, and the supplied electric power will be described later.

[0071] The bias RF power supply 31b is coupled to at least one bias electrode via at least one impedance matching circuit, and is capable of generating a bias RF signal (bias RF electric power). The frequency of the bias RF signal may be the same as the frequency of the source RF signal or different from the frequency of the source RF signal. In one embodiment, the bias RF signal has a frequency lower than the frequency of the source RF signal. In one embodiment, the bias RF signal has a frequency in the range of 100 kHz to 60 MHz. In one embodiment, the bias RF power supply 31b may be capable of generating a plurality of bias RF signals having different frequencies. One or more generated bias RF signals are supplied to at least one bias electrode. In addition, in various embodiments, at least one of the source RF signal and the bias RF signal may be pulsed.

[0072] In addition, the power supply 30 may include a DC power supply 32 coupled to the plasma processing chamber 10. The DC power supply 32 includes a bias DC generation unit 32a. In one embodiment, the bias DC generation unit 32a is connected to at least one bias electrode and is capable of generating a bias DC signal. The generated bias DC signal is applied to at least one bias electrode.

[0073] In various embodiments, the bias DC signal can be pulsed. In this case, a sequence of voltage pulses is applied to at least one bias electrode. The voltage pulse may have a pulse waveform in the shape of a rectangle, a trapezoid, a triangle, or a combination thereof. In one embodiment, a waveform generator for generating a sequence of voltage pulses from a DC signal is connected between the bias DC generator 32a and at least one bias electrode. Therefore, the bias DC generator 32a and the waveform generator constitute a voltage pulse generator. The voltage pulse may have a positive polarity or a negative polarity. In addition, the sequence of voltage pulses may include one or more positive polarity voltage pulses and one or more negative polarity voltage pulses in one cycle. In addition, a bias DC generator 32a may be provided in addition to the RF power supply 31, or a bias DC generator 32a may be provided instead of the bias RF power supply 31b.

[0074] The antenna 14 includes one or more coils. In one embodiment, the antenna 14 may include an outer coil and an inner coil disposed on the same axis. In this case, the RF power supply 31 may be connected to both the outer coil and the inner coil, or to either the outer coil or the inner coil. In the former case, the same RF generator may be connected to both the outer coil and the inner coil, or different RF generators may be connected to the outer coil and the inner coil, respectively.

[0075] A sensor unit 50 for measuring the impedance of the plasma and / or the supplied electric power is provided on the output path of the output electric power of the source RF power supply 31a. In addition, a matching device 60 is provided on the output path of the output electric power, and constitutes a tuning circuit for matching the impedance between the source RF power supply 31a and the plasma processing chamber 10 containing the plasma. In addition, an RF control unit 70 for controlling the source RF power supply 31a and the matching device 60 is included. The RF control unit 70 can be assembled in the control unit 2 and provided as a part of the control unit 2.

[0076] The exhaust system 40 can be connected to the gas exhaust port 10E provided at the bottom of the plasma processing chamber 10, for example. The exhaust system 40 can include a pressure regulating valve and a vacuum pump. The pressure in the plasma processing space 10s can be adjusted by the pressure regulating valve. The vacuum pump can include a turbomolecular pump, a dry pump, or a combination thereof.

[0077] <Tuning circuit for impedance matching>

[0078] Next, use Figure 3 The details of the tuning circuit for impedance matching will be described. Figure 3The figure shows the connection and structure among the source RF power supply 31a, the sensor unit 50, the matching device 60, the RF control unit 70, and the induction coil 80 as the antenna 14. These structures perform feedback control for adjusting the output or operation of the source RF power supply 31a or the matching device 60 based on the difference between the command signal from the outside, for example, the control unit 2 and the electric power measured in the sensor unit 50.

[0079] Specifically, the sensor unit 50 measures the voltage, current, and phase difference between the voltage and current of the high frequency output, converts the measurement data into an analog signal or a digital signal, and sends it to the measurement unit 200 of the RF control unit 70. After the measurement unit 200 converts the measurement data into an internal signal, it sends the internal signal to the supply power calculation unit 202 and / or the impedance calculation unit 204. The supply power calculation unit 202 calculates the supply power (P) to the plasma from the measurement results of the sensor unit 50. In detail, when the voltage (RMS value) measured by the sensor unit 50 is Vrms, the current (RMS value) is Irms, and the phase difference is θ, the supply power (P) to the plasma is calculated by the following formula.

[0080] P = Vrms × Irms × cos (θ) ... Formula (1)

[0081] Similarly, the impedance calculation unit 204 obtains the impedance (Z) between the source RF power source 31 a and the plasma processing chamber 10 from the measurement result of the sensor unit 50 using the following equation (2).

[0082] Z=Vrms / Irms…Formula (2)

[0083] Next, as an example, a command signal from the control unit 2 is input to the external input unit 206. The external input unit 206 to which the command signal from the control unit 2 is input transmits the output power command signal as an internal signal to the output power control unit 208. The output power control unit 208 calculates the output power to be output from the source RF power supply 31a based on the difference between the output power command signal from the external input unit 206 and the supply power measured by the sensor unit 50. In addition, the external input unit 206 to which the command signal from the control unit 2 is input transmits the frequency command signal as an internal signal to the frequency control unit 210. The frequency control unit 210 determines the supply power to the plasma based on the reference frequency command signal from the external input unit 206, and calculates the output frequency for impedance matching based on the impedance measurement result.

[0084] Next, the results calculated by the output power control unit 208 and the frequency control unit 210 are sent to the arbitrary waveform generation unit 212. The arbitrary waveform generation unit 212 generates a waveform obtained by superimposing sine waves of multiple frequency components based on the results calculated by the output power control unit 208 and the frequency control unit 210, and outputs it to the source RF power supply 31a. In the plasma processing method MT1 of the first embodiment described later, the arbitrary waveform generation unit 212 generates a waveform including the first frequency F 1 and the second frequency F 2 In this case, the arbitrary waveform generating unit 212 is configured to independently control the first frequency F 1 and the second frequency F 2 In the plasma processing method MT2 of the second embodiment described later, the arbitrary waveform generation unit 212 generates a waveform obtained by superimposing sine waves of multiple frequency components included in a bandwidth ΔF described later. In this case, the arbitrary waveform generation unit 212 is configured to be able to expand and reduce the bandwidth ΔF.

[0085] Next, the power amplifier 214 of the source RF power source 31a amplifies the sine wave output from the arbitrary waveform generator 212 with a desired gain using the DC power supplied from the DC power source 216. The power amplifier 214 includes a plurality of FETs (field effect transistors) for high-frequency power amplification, a distributor for distributing the waveform from the arbitrary waveform generator 212 to each FET, and a synthesizer for synthesizing the output power of each FET.

[0086] Next, the matching device 60 including the variable capacitor 218 constitutes a tuning circuit for matching the impedance of the plasma by the frequency of the output power of the source RF power supply 31a and the capacitor component of the variable capacitor 218. As for the variable capacitor 218, as an example, a vacuum capacitor with high durability against the high voltage generated by the resonance of the impedance can be used. In addition, the variable capacitor 218 is connected to an actuator 220 such as an electric motor. The matching device control unit 222 of the RF control unit 70 drives the actuator 220 based on the variable capacitor position instruction signal from the external input unit 206 to adjust the capacitance of the capacitor. As a result, when the plasma is generated, the capacitance is adjusted to match the impedance within the frequency range calculated by the frequency control unit 210.

[0087] The source RF power source 31a and the RF control unit 70 may be provided in plurality. As an example, a configuration may be provided in which a source RF power source 31a as a main source and a source RF power source 31a as a sub-source are provided, and one RF control unit 70 is provided for each of the main source and the sub-source. In this case, the source RF power source 31a as the main source may output a first frequency F described later.1 The first output power E 1 The second frequency F described later is output from the source RF power supply 31a as the auxiliary source. 2 The second output power E 2 In addition, a configuration may be adopted in which a plurality of RF control units 70 other than the arbitrary waveform generation unit 212 are provided, and each RF control unit transmits a signal including the first frequency F described later to one arbitrary waveform generation unit 212. 1 and the second frequency F 2 In this case, the arbitrary waveform generation unit 212 may generate a waveform obtained by superimposing sine waves of a plurality of frequency components and output the waveform to one source RF power source 31a.

[0088] <First embodiment>

[0089] Next, use Figure 4 7 to 8 illustrate a plasma processing method MT1 according to a first embodiment. In the plasma processing method MT1 according to the first embodiment, a first frequency F is used to maintain plasma. 1 The first output power E 1 , and the second frequency F 2 The second output power E 2 That is, using the second frequency F 2 The second output power E 2 To search and determine the resonance point of the impedance, the first frequency F 1 Tuned to the determined resonance point. In addition, the resonance point is the first resonance point FP 1 Or the second resonance point FP 2 , the anti-resonance point is the first anti-resonance point RP 1 Or the second anti-resonance point RP 2 The following describes the details of the specific method.

[0090] Figure 4 1 is a flowchart showing an overview of the plasma processing method MT1 according to the first embodiment. Figure 4 First, let the second frequency F 2 The impedance resonance point (first resonance point FP) is scanned in the direction of increasing the supplied electric power (resonance side) to obtain the impedance resonance point (first resonance point FP 1 ) (step ST10). Next, the second frequency F 2 The supplied electrical power P 2 The maximum frequency is determined as the first resonance point FP 1 , stop the second frequency F 2 Next, the first frequency F 1 Scan to the determined first resonance point FP1 , so that it is tuned (step ST14). Then, after the required time (either the first control cycle C1 or the second control cycle C2 described later) has passed, enter the next step (step ST16). Then, compare the reflected electric power with the threshold and determine the size (step ST18). If the reflected electric power is below the threshold, return to step ST16. If the reflected electric power exceeds the threshold, it is determined that the first resonance point FP 1 Moved to the second resonance point FP 2 , and return to step ST10. By repeating the above steps ST10 to ST18 and periodically performing matching control, the first frequency F 1 The resonance point moves in accordance with the impedance fluctuation and is tuned accordingly.

[0091] Next, use Figure 5 The first control period C1 and the second control period C2 are described. Figure 5 The state of the control cycle of impedance, reflected power, and matching control when the output power of the source RF power supply 31a or the chamber pressure (or gas condition) is changed stepwise according to an external command. In addition, the meaning of the first control cycle C1 and the second control cycle C2 is the same in the second embodiment described later.

[0092] Due to the step change of the output power or the pressure (or gas condition) in the chamber based on the external command signal, the impedance of the plasma will change. Immediately after the step, the plasma is in a transition state, and the change of the impedance at this time becomes sharp. In addition, as time passes, the plasma changes from the transition state to the stable state, and the change of the impedance becomes gentle. In order to stabilize the matching control, it is preferred to suppress excessive changes in the frequency of the output power. Therefore, in one embodiment, according to the various states of the plasma accompanied by the step change of the external command signal, the control period is switched to a short period (C1) or a long period (C2) to change the response.

[0093] When the time when the output of the output power of the source RF power supply 31a starts is set to T1, the plasma immediately after time T1 becomes a transition state. In the transition state, the control period is selected to be a short period (C1) in order to respond to the rapid change of impedance. Specifically, the short-period control period C1 is less than 100 μsec. Thus, matching control can be performed following the rapid change of impedance. The lower limit of the short-period control period is not particularly limited, and for example, it can be more than 10 μsec.

[0094] When the time T1 changes to the time T2 when the reflected electric power reaches below the threshold, it becomes a waiting period for the stable state of the plasma, and the matching control is transferred to the step of monitoring the fact that the reflected electric power is below the threshold for a certain time (ΔST). After it is determined that the reflected electric power is always below the threshold from time T2 to time (T2+ΔST), the plasma is regarded as a stable state, and the control cycle is changed from a short cycle (C1) to a long cycle (C2). The long-cycle control cycle C2 is specifically less than 1 sec. Thus, it is possible to follow the change in impedance in the stable state of the plasma to perform matching control. In addition, the long-cycle control cycle is, for example, more than 100 μsec.

[0095] At time T3, for example, when a step is made in the chamber pressure, the same steps as those immediately after time T1 are performed. In order to cope with the transient state of the plasma after the step, the long cycle (C2) is transferred to the short cycle (C1) immediately after time T3. After that, after reaching time T4 when the reflected electric power becomes below the threshold, the fact that the reflected electric power is always below the threshold during the time ΔST is monitored. When it is determined that the reflected electric power is always below the threshold from time T4 to time (T4+ΔST), the plasma is regarded as a stable state, and the control cycle is changed from the short cycle (C1) to the long cycle (C2).

[0096] Next, use Figures 6A to 6C and Figures 7A to 7C The details and significance of each step of the plasma processing method MT1 of the first embodiment are described. In each figure, from the top, the impedance between the source RF power supply 31a and the plasma, the first frequency F 1 The first output power E 1 and the second frequency F 2 The second output power E 2 , the first frequency F 1 The supplied electrical power P 1 and the second frequency F 2 The supplied electrical power P 2 , and the total amount of supplied electric power PT. In addition, the impedance diagram is a diagram for the convenience of explaining the details and meaning of each step of the plasma processing method MT1, and does not mean that the impedance at an arbitrary frequency is measured or calculated in each step.

[0097] Fig. 6A represents the impedance, the first and second output electric powers E before starting step ST10 1 、E 2 , supply power P 1 , P 2And the total amount of electrical power supplied PT. Output electrical power E at each frequency 1 、E 2 There is no resonance point FP with impedance 1 Tuning, therefore, part of it is reflected (reflected electric power), and the supply electric power P to the plasma 1 , P 2 That is, the first frequency F 1 The supplied electrical power P 1 Less than the first frequency F 1 The first output power E 1 (P 1 <E 1 ), the second frequency F 2 The supplied electrical power P 2 Less than the second frequency F 2 The second output power E 2 (P 2 <E 2 ). In addition, the total amount of electric power supplied to the plasma is P 1 +P 2 (<E 1 +E 2 ). The closer the frequencies are to the first resonance point FP 1 The better the impedance is matched, the greater the electrical power supplied to the plasma.

[0098] The second frequency F 2 The second output power E 2 The effect on plasma is minimal, so it is set relative to the first frequency F 1 The first output power E 1 The electric power which is relatively small and can be detected by the measuring unit 200. For example, in the first output electric power E 1 When the power is above 100W, the second output power E 2 The power range is set to 0.1 to 1% (0.1 to 1 W), and the measuring unit 200 includes a high-frequency amplifier circuit and an A / D circuit having a gain and a resolution capable of detecting the power range.

[0099] Figure 6B Indicates that the second frequency F 2 From F 2 (1) Scan to F 2 (2), calculate F 2 (1)~F 2 (2) The power spectrum between the two, searching for the first resonance point FP 1 Steps (steps ST10 and ST12). 2 From F 2 (1) Scan to F2 (2), the impedance changes with the sweep. In the example shown in the figure, when the second frequency F 2 (1) To the first resonance point FP 1 The impedance decreases with the sweep. In addition, from the first resonance point FP 1 To the first anti-resonance point RP 1 The impedance increases with the sweep. In addition, when the frequency is from the first anti-resonance point RP 1 As mentioned above, by the second frequency F 2 Scanning can obtain the characteristics of the impedance waveform without affecting the maintenance of plasma.

[0100] At the second frequency F 2 When scanning, the impedance decreases, so that the reflected electric power decreases and the supplied electric power increases. In one embodiment, the second frequency F is calculated 2 The supplied electrical power P 2 The power spectrum of the power spectrum is taken as the peak value, that is, the power is the maximum (P 2MAX (1)) is regarded as the first resonance point FP 1 In addition, in one embodiment, the total amount of supplied electrical power PT (P 1 +P 2 ), the total amount of electric power supplied during this period PT becomes the maximum (PT MAX (1)) is regarded as the first resonance point FP 1 In one embodiment, the frequency at which the reflected electric power becomes minimum is regarded as the first resonance point FP. 1 In addition, as the calculation of the second frequency F 2 The supplied electrical power P 2 The power spectrum method can use the discrete Fourier transform of the measurement signal or the heterodyne gain detection method used in wireless signals.

[0101] In addition, at the second frequency F 2 When scanning, the first frequency F 1 The frequency is limited to the frequency that can stably maintain the plasma. In addition, it can be 2 The first frequency F 1 Alternatively, it can be based on the first resonance point FP 1 The intermediate result of the search is to determine the frequency that can stably maintain the plasma at the second frequency F 2 The first frequency F is scanned 1 That is, by making the second frequency F 2 Scanning is performed to determine a frequency range that can stably maintain the plasma, so that the first frequency F1 In the example shown in the figure, when the second frequency F 2 (1) To the first resonance point FP 1 The impedance decreases in stages, so it can be determined that even if the first frequency F 1 The plasma can be stably maintained even when the first frequency F is changed within this range. 1 When the first frequency F changes, 1 The second frequency F 2 The scanning speed (frequency change speed) is smaller than the second frequency F 2 Alternatively, the first frequency F 1 With the second frequency F 2 The scanning speed is the same speed, following the second frequency F 2 Thus, it is possible to use the first frequency F 1 The first output power E 1 In the state of stably maintaining the plasma, the second frequency F which has little influence on the maintenance of the plasma is used. 2 Scan to determine the first resonance point FP 1 .

[0102] Figure 6C Indicates that when determining the first resonance point FP 1 Then the first frequency F 1 Scan and tune it to the resonance point FP (step ST14). The first resonance point FP 1 Through the second frequency F 2 Therefore, the first frequency F can be suppressed during scanning. 1 Exceeding the first resonance point FP 1 And move to the first anti-resonance point RP 1 Thus, the first anti-resonance point RP can be suppressed. 1 The rapid change of impedance on the one side may cause insufficient supplied power, and matching control can be performed while stabilizing the plasma.

[0103] Next, use Figure 7A to Figure 7C In the first frequency F 1 Tuned to the first resonance point FP 1 Afterwards, due to the change in plasma impedance, the resonance point changes from the first resonance point FP 1 Move to the second resonance point FP 2 The re-matching steps in the case of (steps ST10 to ST18 when the reflected electric power exceeds the threshold in step ST18) are performed again.

[0104] Fig. 7AIndicates at Figure 6C the first frequency F shown 1 (2) Tuned to the first resonance point FP 1 After that, due to the impedance variation of the plasma, the first resonance point FP 1 moves to the second resonance point FP 2 , a state where the reflected electric power exceeds the threshold. The resonance point moves away from the impedance matching point, and the electric power supplied to the plasma decreases. In the re-matching step, the first frequency F 1 is matched with the second resonance point FP 2 .

[0105] Figure 7B Indicates that by scanning the second frequency F 2 between F 2 (3) and F 2 (4), the second resonance point FP 2 is searched for and determined again (steps ST10 and ST12 when executed again in the case where the reflected electric power exceeds the threshold in step ST18). In one embodiment, in the same manner as the steps shown in FIG. 6(b), the peak of the power spectrum of the supplied electric power P 2 of the second frequency F, that is, the frequency at which the power becomes maximum (P 2 (2)) is regarded as the second resonance point FP 2MAX . Additionally, in one embodiment, during the scan of the second frequency F 2 , the total amount of supplied electric power PT (P 2 (2) + P 1 (2)) is measured, and the frequency at which the total amount of supplied electric power PT becomes maximum (PT 2 (2)) is regarded as the second resonance point FP MAX . Additionally, in one embodiment, the frequency at which the reflected electric power becomes minimum is regarded as the second resonance point FP 2 . 2 .

[0106] Figure 7C Indicates the step of scanning the first frequency F 1 (2) in the direction of the determined second resonance point FP 2 and tuning it to the second resonance point FP 2 (step ST14 when executed again in the case where the reflected electric power exceeds the threshold in step ST18).

[0107] By Figure 7A to Figure 7C the steps shown, even if the first resonance point FP 1 moves to the second resonance point FP 2 , the second resonance point FP 2 can be determined, and the first frequency F1 Tuning.

[0108] <Second embodiment>

[0109] Next, the plasma processing method MT2 according to the second embodiment will be described with reference to the drawings. In the plasma processing method MT2 according to the second embodiment, the output power E for maintaining the plasma is 11 Frequency F 11 The frequency F for maintaining the plasma is also used in the search for the resonance point of the impedance. 11 The output power E 11 , when searching for the resonance point, the frequency F 11 The bandwidth ΔF is adjusted. Thus, the frequency F 11 Gradually approach the resonance point and tune to the resonance point. Here, "frequency F 11 The bandwidth ΔF" means that the frequency F 11 The method includes two or more frequency components, and the difference between the highest frequency component and the lowest frequency component is ΔF.

[0110] Figure 8 1 is a flowchart showing an overview of the plasma processing method MT2 according to the second embodiment. Figure 8 First, set the output power E 11 Frequency F 11 The bandwidth ΔF is increased (step ST20). In addition, in step ST20, which is repeatedly executed in step ST34 described later, the bandwidth ΔF is increased. Next, the frequency F 11 The supplied electric power is scanned in the direction (resonance side) in which the supplied electric power increases (step ST22). Next, the frequency F is determined. 11 The power P supplied during the scan 11 The frequency F becomes the maximum and the scanning stops (step ST24). 11 Scan to determine the supply power P 11 Then, the frequency F is reduced to the maximum value and the frequency is tuned (step ST26). 11The bandwidth ΔF (step ST28) is then compared with the threshold value to determine the size (step ST30). If the reflected electric power is below the threshold value in step ST30, proceed to step ST32. If the reflected electric power exceeds the threshold value in step ST30, return to step ST22. In step ST32, after the required time (either the first control cycle C1 or the second control cycle C2) has passed, proceed to step ST34 (step ST32). Next, the reflected electric power is compared with the threshold value to determine the size (step ST34). If the reflected electric power is below the threshold value in step ST34, return to step ST32. If the reflected electric power exceeds the threshold value in step ST34, return to step ST20. By repeatedly performing the above steps ST20 to ST34 and periodically performing matching control, the frequency F 11 The resonance point moves in accordance with the impedance fluctuation and is tuned accordingly.

[0111] In the above description, the first control cycle C1 and the second control cycle C2 in step ST32 are the same as those described in the first embodiment.

[0112] Next, the details and significance of each step of the plasma processing method MT2 of the second embodiment are described using FIG9 and FIG10. In each of FIG9 and FIG10, each figure shows the impedance between the source RF power supply 31a and the plasma, the frequency F 11 The output power E 11 , frequency F 11 The supplied electrical power P 11 The impedance diagram is a diagram for convenience in explaining the details and meaning of each step of the plasma processing method MT2, and does not mean that the impedance at any frequency is measured or calculated in each step.

[0113] Fig. 9A The impedance and frequency F at each frequency when the bandwidth ΔF is set to the initial value ΔF(1) in step ST20 are shown. 11 The output power E 11 , Supply power P according to frequency 11 And the total amount of electrical power supplied PT. Here, the first frequency F 11 With the lowest frequency component F 11 (1) To the highest frequency component F 11 The power supplied to the plasma is F 11 (1) to F 11 (1) + △F (1). In addition, the supplied power P 11The integrated amount of becomes the total amount of electric power supplied to the plasma, PT. Fig. 9B In the following figures, only the supplied electric power P is recorded. 11 The total amount of the supplied electric power PT is shown in the figure, omitting the supplied electric power P 11 Record of the picture.

[0114] The initial value ΔF(1) of the bandwidth ΔF is explained. In an ICP-type plasma processing device in which the base frequency of the source RF power supply 31a is 13 MHz or 27 MHz, the frequency width between the resonance point and the anti-resonance point is assumed to be 10 kHz to 100 kHz as an example. Therefore, the initial value ΔF(1) of the bandwidth is also preferably 10 kHz to 100 kHz. However, in the case where the frequency width between the resonance point and the anti-resonance point is outside the above range due to the chamber pressure or gas conditions, the actual frequency width between the resonance point and the anti-resonance point can be calculated, and the initial value ΔF(1) of the bandwidth can be used as the calculated width. Alternatively, the width of the frequency having an impedance value half of the peak value (full width at half maximum) can be calculated on both sides of the peak value of the impedance at the resonance point, and the initial value ΔF(1) of the bandwidth can be determined in a manner not less than the full width at half maximum.

[0115] Fig. 9B Indicates that the frequency F 11 Take the frequency component with the lowest frequency (the frequency component with the highest power as shown in the output power diagram) from F 11 (1) becomes F 11 (2) Scanning to find the total amount of supplied electric power PT to be the maximum (PT MAX (1)) at the frequency (step ST22). 11 In the scanning, the frequency is gradually increased (or decreased) for each frequency component while maintaining the bandwidth ΔF(1) and the value of the electric power of each frequency component. 11 The shape of the graph does not change before and after scanning.

[0116] exist Fig. 9B In the output power E 11 In the above equation, the lowest frequency component is the largest electric power, the highest frequency component is the smallest electric power, and the electric power is gradually reduced from the lowest frequency to the highest frequency to form the output electric power E. 11 Thus, even when the highest frequency component moves to the first anti-resonance point RP during scanning, 1 side, it can also be located at the first resonance point FP 1 The lowest frequency component on the side is used to maintain the plasma.

[0117] In addition, Fig. 9BIn the scanning, when the lowest frequency component exceeds the first resonance point FP 1 Before that, the total amount PT of the supplied electric power becomes maximum. In other words, in step ST24, the total amount PT of the supplied electric power becomes maximum (PT MAX (1)) frequency, when the lowest frequency component exceeds the first resonance point FP 1 The reason is as follows. In the output path from the source RF power source 31a, the reflected electric power is generated for each frequency component in correlation with the electric power of each frequency component. That is, when the highest frequency component exceeds the first resonance point FP 1 After that, the reflected electric power of the highest frequency component increases in correlation with the electric power of the highest frequency component. On the other hand, the first resonance point FP has not yet been reached at this time. 1 The lowest frequency component, close to the first resonance point FP 1 , so that the reflected electric power is reduced in relation to the electric power of the lowest frequency component. Therefore, at the highest frequency exceeding the first resonance point FP 1 After that, the total amount of reflected electric power also temporarily decreases, and the total amount of supplied electric power PT also increases. After that, the scanning is continued, and the frequency component of a certain part exceeds the first resonance point FP 1 At the moment, it exceeds the first resonance point FP 1 The increase in the reflected electric power of the frequency component exceeds the first resonance point FP 1 When the increase in reflected power exceeds the decrease, the total amount of supplied power decreases. Therefore, when the lowest frequency component exceeds the first resonance point FP 1 Previously, the total amount PT of supplied electric power became maximum.

[0118] In addition, Fig. 9B The frequency F used as the stop point of the scan 11 (2) The total amount of supplied electric power PT can be maximized (PT MAX (1)) is determined. In this case, it can be whether the total amount of supplied electric power PT has reached the maximum (PT MAX (1)) is determined when the total amount of supplied electric power PT starts to decrease and the required electric power is reduced (for example, 10W to 20W). At this time, it is determined that the total amount of supplied electric power PT becomes maximum (PT MAX That is, in this case, the step ST22 of “making the frequency F 11 Scanning in the direction of increasing the supplied electric power (resonance side), "including scanning from the supplied electric power to the reduced direction until the required electric power is reduced. Alternatively, it can be, at a frequency F 11The threshold value of the total amount of supplied electric power PT is set so that the total amount of supplied electric power PT does not fall below the electric power required to maintain the plasma, and the stop point of the scan is determined with reference to the threshold value. Alternatively, the threshold value of the reflected electric power is set so that the reflected electric power does not exceed the value of the tolerable reflected electric power of the source RF power supply 31a, and the stop point of the scan is determined with reference to the threshold value.

[0119] Fig. 9C Indicates that the frequency component with the lowest frequency (the frequency component with the largest electric power shown in the graph of output electric power) is moved from F 11 (2) Scan until the supplied power reaches the maximum (PT MAX (1)) Frequency F 11 Step (3) (step ST26) It may be that at the time after scanning, the highest frequency component exceeds the first resonance point FP 1 .

[0120] Fig.9D Indicates that the frequency F 11 The step of reducing the bandwidth ΔF(1) to ΔF(2) (step ST28). Preferably, when reducing the bandwidth ΔF in step ST28, the frequency F 11 The total amount of output power does not change before and after shrinking. Fig.9D In the example shown, the frequency F is increased by increasing the power of the lowest frequency component while narrowing the bandwidth ΔF. 11 The total amount of output electric power does not change before and after reduction.

[0121] exist Fig.9D In the embodiment, the reduction amount of the bandwidth ΔF can be determined by the required control target number of times until the reflected electric power determined in step ST30 becomes less than the threshold value. As an example, when the control target number of times is n, when ΔF(1) is reduced to ΔF(2) in step ST28, ΔF(1) / n is subtracted from the bandwidth ΔF. Similarly, each time step ST28 is repeatedly performed in step ST30, ΔF(1) / n is subtracted from the bandwidth ΔF. That is, in this case, in step ST28 repeated for the kth time in step ST30, the value of the bandwidth ΔF is ΔF(1)-k·ΔF(1) / n. In addition, as an example, when ΔF(1) is reduced to ΔF(2) in step ST28, the bandwidth ΔF is multiplied by 1 / m. Similarly, each time step ST28 is repeatedly performed in step ST30, ΔF is multiplied by 1 / m. That is, in this case, in step ST28 repeated for the kth time in step ST30, the value of the bandwidth ΔF is ΔF(1) / m k .

[0122] Fig.9E Indicates that the frequency F 11 From F11 (3) Scan to F 11 (4) Search for the total amount of supplied electric power PT to be the maximum (PT MAX (2)) the frequency step (step ST22 when repeatedly executed in step ST30). Fig.9E In the example, the bandwidth ΔF is reduced from ΔF(1) to ΔF(2), so the total amount of supplied electric power PT becomes maximum (PT MAX (2)) and the total amount of supplied electric power PT becomes maximum when the bandwidth ΔF is ΔF(1) (PT MAX However, in this case, too, the total amount of supplied electric power PT becomes maximum (PT) for the same reason as above. MAX (2)) frequency, when the lowest frequency component exceeds the first resonance point FP 1 was determined before.

[0123] Fig.9F Indicates that the frequency F 11 From F 11 (4) Scan until the total amount of supplied electric power PT reaches the maximum (PT MAX (2)) Frequency F 11 Step (5) (step ST26 when repeatedly executed in step ST30) may be that at the time after scanning, the highest frequency component exceeds the first resonance point FP 1 .

[0124] Next, about Figures 9A to 9F By executing steps ST20 to ST28, the frequency F 11 The bandwidth ΔF is reduced from ΔF(1) to ΔF(2) ( FIG. 9A to FIG. 9D ). Then, when the reflected electric power exceeds the threshold in step ST30, the process returns to step ST22 and scans and searches again between the frequencies F(3) and F(4). Thus, it is determined that the total amount PT of the supplied electric power becomes the maximum when the bandwidth ΔF is ΔF(1) (PT MAX (1)) gradually approaches the first resonance point FP 1 The frequency (the total amount of electric power supplied PT becomes the maximum (PT MAX (2)) Frequency)( Fig.9E ). After that, the total amount of supplied electric power PT determined by scanning becomes the maximum (PT MAX (2)) frequency (F 11 (5)), frequency F 11 Gradually approaching the first resonance point FP 1 Afterwards, by Figures 9A to 9FThe steps (steps ST22 to ST30) are repeated a finite number of times to set the frequency F 11 Tuned to the first resonance point FP 1 In addition, the frequency F 11 The bandwidth ΔF also changes from wide to single. The single bandwidth ΔF is a concept including a limited width corresponding to the frequency resolution that can be measured by a measuring instrument such as a spectrum analyzer.

[0125] Figure 9G Indicates that by repeatedly Figures 9A to 9F Steps (steps ST22 to ST30), the bandwidth ΔF is close to single, the frequency F 11 Tuned to the first resonance point FP 1 state. At frequency F 11 Tuned to the first resonance point FP 1 Under the impedance matching state, the electric power supplied to the plasma can be maximized.

[0126] Next, use Figures 10A to 10F Description At frequency F 11 Tuned to the first resonance point FP 1 Afterwards, due to the change in plasma impedance, the resonance point changes from the first resonance point FP 1 Move to the second resonance point FP 2 The re-matching step in the case (steps ST20 to ST34 are repeatedly executed when the reflected electric power exceeds the threshold in step ST34).

[0127] Fig. 10A Indicates that Figure 9G As shown in the frequency F 11 Tuned to the first resonance point FP 1 After that, due to the change in the impedance of the plasma, the first resonance point FP 1 Move to the second resonance point FP 2 , the reflected electric power exceeds the threshold value. The resonance point moves away from the impedance matching point, and the electric power supplied to the plasma decreases. In the re-matching step, the frequency F 11 and the second resonance point FP 2 match.

[0128] Fig. 10B Indicates that the frequency F 11 The step of expanding the bandwidth ΔF to ΔF(3) (step ST20 when repeatedly executed in step ST34). 1 Tuning frequency F 11 (6) There is a change in impedance close to the second anti-resonance point RP 2In this case, when the bandwidth ΔF is expanded, the power supplied to the plasma is reduced, which may become the cause of plasma extinguishing. Therefore, in this case, when the bandwidth ΔF is expanded, the power supplied to the plasma is monitored, and the bandwidth ΔF is adjusted to be able to supply enough power to maintain the plasma or a judgment is made. Alternatively, it can be that at the second anti-resonance point RP 2 The second resonance point FP has a gentler change in impedance than the side 2 Frequency F in the side direction 11 After the scan, adjust the bandwidth ΔF.

[0129] Fig. 10C Indicates that the frequency F 11 (6) Scan to the second resonance point FP 2 Side F 11 (7) Search for the total amount of supplied electric power PT to be the maximum (PT MAX (3)) The frequency step (steps ST22 and ST24 when repeatedly executed in step ST34).

[0130] Fig. 10D Indicates that the frequency F 11 (7) Scan until the total amount of supplied electric power PT reaches the maximum (PT MAX (3)) Frequency F 11 Step (8) (step ST26 when repeatedly executed in step ST34).

[0131] Fig.10E Indicates that the frequency F 11 The step of reducing the bandwidth ΔF(3) of (8) to ΔF(4) (step ST28 when repeatedly executing step ST34).

[0132] Fig.10F Indicates that by repeatedly Figure 10C to Figure 10E In the steps shown (steps ST22 to ST28), the frequency F 11 Tuned to the second resonance point FP 2 status.

[0133] in addition, Figure 10D to Figure 10F The details and meaning of the steps shown are the same as those in the above Figure 9C to Figure 9G The steps are the same as described in .

[0134] Through the above Figures 10A to 10F The re-matching step shown in the figure shows that even if the resonance point changes from the first resonance point FP due to impedance variation, 1 Move to the second resonance point FP 2 , it is also possible to change the frequency F 11 Tuned to the second resonance point FP 2, and make its bandwidth ΔF single. At frequency F 11 Tuned to the second resonance point FP 2 Under the impedance matching state, the electric power supplied to the plasma can be maximized.

[0135] The preferred embodiment of the present invention has been described above, but a preferred effect can be obtained by combining the first embodiment and the second embodiment. As an example, in the plasma processing method MT1 of the first embodiment, the first frequency F 1 With bandwidth ΔF, the first frequency F 1 The frequency F of the plasma processing method MT2 of the second embodiment 11 The same is true for scanning.

[0136] In addition, the present invention is not limited to the above-mentioned embodiments, and can be deformed and changed within the scope of the main purpose of the present invention. As an example, in the above-mentioned embodiments, the etching device using plasma is mainly used for description, but it can also be applied to processing devices and manufacturing methods such as semiconductors and liquid crystal displays that use plasma such as CVD and ashing, and other processing devices and manufacturing methods that require impedance matching of high-frequency power supplies.

[0137] In addition, for example, the constituent elements of the above-mentioned embodiments can be combined arbitrarily. From this arbitrary combination, of course, the functions and effects of the various constituent elements involved in the combination can be obtained, and other functions and other effects that are obvious to those skilled in the art based on the records of this specification can be obtained. In addition, the effects recorded in this specification are merely illustrative or exemplary, and not restrictive. That is, the technology of the present invention can obtain the above-mentioned effects and other effects that are obvious to those skilled in the art based on the records of this specification, or the technology of the present invention can obtain other effects that are obvious to those skilled in the art based on the records of this specification, instead of the above-mentioned effects.

[0138] Description of Reference Numerals

[0139] E 1 The first output electric power, E 2 Second output power, F 1 First frequency, F 2 second frequency, FP resonance point, 1 plasma processing device, 2 control unit, 10 plasma processing chamber, 14 antenna, 31 RF power supply.

Claims

1. A plasma processing apparatus, characterized in that, comprising: a plasma processing chamber; an antenna disposed above or over the plasma processing chamber; an RF power supply electrically connected to the antenna and capable of controlling the frequency of the output electric power; and a control unit, wherein the RF power supply can output a first output electric power having a first frequency and a second output electric power having a second frequency, and the second output electric power is smaller than the output electric power having the first frequency, and the control unit can perform: step (a), scanning the second frequency to search for and determine a resonance point; and step (b), tuning the first frequency to the resonance point.

2. The plasma processing apparatus according to claim 1, characterized in that: in step (a), the control unit scans the second frequency in a direction in which the supply electric power to the plasma processing chamber becomes maximum, and determines the frequency at which the supply electric power becomes maximum as the resonance point.

3. The plasma processing apparatus according to claim 1 or 2, characterized in that: in step (a), the control unit controls the first frequency to be in any one of the following states (a1) to (a3): (a1) fixing the first frequency; (a2) changing the first frequency with a delay compared to the scan of the second frequency within the range where the second frequency is scanned; (a3) changing the first frequency following the scan of the second frequency within the range where the second frequency is scanned.

4. The plasma processing apparatus according to claim 1 or 2, characterized in that: the control unit can perform step (c), after tuning the first frequency to the resonance point, comparing the reflected electric power with a threshold value after a first control period when the plasma is in a transitional state, and comparing the reflected electric power with the threshold value after a second control period when the plasma is in a stable state, and when the reflected electric power exceeds the threshold value in step (c), the control unit performs step (a) and step (b) again.

5. A plasma processing method, which is a plasma processing method using a plasma processing apparatus, characterized in that: the plasma processing apparatus includes: a plasma processing chamber; an antenna disposed above or over the plasma processing chamber; and an RF power supply electrically connected to the antenna and capable of controlling the frequency of the output electric power, wherein the RF power supply can output a first output electric power having a first frequency and a second output electric power having a second frequency, and the second output electric power is smaller than the output electric power having the first frequency, and the plasma processing method includes: step (a), scanning the second frequency to search for and determine a resonance point; and step (b), tuning the first frequency to the resonance point.

6. The plasma processing method according to claim 5, characterized in that: In the step (a), the second frequency is swept in a direction in which the electric power supplied to the plasma processing chamber becomes maximum, and the frequency at which the electric power supplied becomes maximum is determined as the resonance point.

7. The plasma treatment method according to claim 5 or 6, Features: In the step (a), the first frequency is controlled to be in any state selected from the following (a1) to (a3): (a1) fixing the first frequency; (a2) changing the first frequency with a delay relative to the sweep of the second frequency within a range in which the second frequency is swept; (a3) The first frequency is changed in accordance with the sweep of the second frequency within a range in which the second frequency is swept.

8. The plasma treatment method according to claim 5 or 6, Features: The method comprises the step (c), after tuning the first frequency to the resonance point, comparing the reflected electric power with a threshold value after a first control period when the plasma is in a transient state, and comparing the reflected electric power with a threshold value after a second control period when the plasma is in a stable state. When the reflected electric power exceeds the threshold value in the step (c), the steps (a) and (b) are performed again.

9. A plasma processing device, It is characterized in that include: a plasma processing chamber; an antenna disposed on or above the plasma processing chamber; an RF power source electrically connected to the antenna and capable of controlling the frequency of output electric power; and Control Department, The RF power source is capable of outputting electric power having a bandwidth including frequency components having two or more frequencies, The control unit is capable of performing: Step (a), setting the bandwidth of the frequency of the output electric power to a first bandwidth, scanning the frequency, and determining a first frequency at which the electric power supplied to the plasma processing chamber becomes maximum; and Step (b) sets the bandwidth to a second bandwidth smaller than the first bandwidth, scans the frequency of the output power, and determines a second frequency at which the power supplied to the plasma processing chamber becomes maximum.

10. The plasma processing apparatus according to claim 9, Features: The control unit can execute step (c) of comparing the reflected power with a threshold value after determining the second frequency at which the power supplied to the plasma processing chamber becomes maximum in step (b), When the reflected electric power exceeds the threshold value in the step (c), the control unit executes the steps (a) and (b) again.

11. The plasma processing apparatus according to claim 10, Features: The control unit is capable of executing step (d), in which, when the reflected electric power is below the threshold value in step (c), the reflected electric power is compared with the threshold value after a first control cycle when the plasma is in a transient state, and the reflected electric power is compared with the threshold value after a second control cycle when the plasma is in a stable state, In the step (d), when the reflected electric power exceeds the threshold value, the control unit executes the steps (a) to (c) again.

12. A plasma processing method, which is a plasma processing method using a plasma processing device, Features: The plasma processing device comprises: a plasma processing chamber; an antenna disposed on or above the plasma processing chamber; and an RF power supply, which is electrically connected to the antenna and is capable of controlling the frequency of output electric power, The RF power source is capable of outputting electric power having a bandwidth including frequency components having two or more frequencies, The plasma treatment method comprises: Step (a), setting the bandwidth of the frequency of the output electric power to a first bandwidth, scanning the frequency, and determining a first frequency at which the electric power supplied to the plasma processing chamber becomes maximum; and Step (b) sets the bandwidth to a second bandwidth smaller than the first bandwidth, scans the frequency of the output power, and determines a second frequency at which the power supplied to the plasma processing chamber becomes maximum.

13. The plasma processing method according to claim 12, Features: The method comprises the step (c), after determining in the step (b) the second frequency at which the electric power supplied to the plasma processing chamber becomes the maximum, comparing the reflected electric power with a threshold value, When the reflected electric power exceeds the threshold value in the step (c), the steps (a) and (b) are performed again.

14. The plasma processing method according to claim 13, Features: The method comprises the steps of: when the reflected electric power is below the threshold value in the step (c), comparing the reflected electric power with the threshold value after a first control cycle when the plasma is in a transient state, and comparing the reflected electric power with the threshold value after a second control cycle when the plasma is in a stable state, When the reflected electric power exceeds the threshold value in the step (d), the steps (a) to (c) are performed again.

Images