Plasma processing device and RF generator

Abstract

Provided is a technique capable of efficiently generating RF signals. This plasma processing device comprises a chamber, and an RF generator configured to generate RF signals, wherein the RF generator includes: a DC power source; a resonant circuit; an isolation circuit configured to supply a current from the DC power source to the resonant circuit and to prevent transmission of resonant energy from the resonant circuit to the DC power source; a capacitor electrically connected to an output of the resonant circuit; and a switching circuit in which, in an OFF state, the resonant energy is stored in the resonant circuit, and in an ON state, an RF signal having a resonance frequency continues to oscillate between the resonant circuit and the switching circuit.

Description

Plasma processing apparatus and RF generator

[0001] The present disclosure relates to plasma processing apparatus and RF generators.

[0002] Patent Document 1 discloses a system for processing wafers using a matchless plasma source. Patent Document 2 discloses a DC pulse power supply for plasma processing equipment that can improve the rise and fall characteristics of a DC pulse voltage. Patent Document 3 discloses a power supply for plasma generation that can protect a switching element from transient load fluctuations specific to plasma loads.

[0003] Patent Publication No. 2021-500701 Patent Publication No. 6613411 Japanese Patent Laid-Open Publication No. 2004-080846

[0004] An object of the present disclosure is to provide a plasma processing apparatus and an RF generator that can efficiently generate an RF signal.

[0005] In one exemplary embodiment of the present disclosure, a plasma processing apparatus includes a chamber and an RF generator configured to generate an RF signal to generate plasma in the chamber, the RF generator including: a DC power supply; a resonant circuit electrically connected to the DC power supply; an isolation circuit electrically connected to the resonant circuit and configured to supply current from the DC power supply to the resonant circuit and prevent transfer of resonant energy from the resonant circuit to the DC power supply; a capacitor electrically connected to an output of the resonant circuit; and a switching circuit electrically connected between a node between the resonant circuit and the isolation circuit and a ground potential and configured to switch between an off state that stops supplying current from the resonant circuit to the ground potential and an on state that supplies current from the resonant circuit to the ground potential, wherein in the off state, resonant energy is stored in the resonant circuit and in the on state, oscillation of an RF signal having a resonant frequency continues between the resonant circuit and the switching circuit.

[0006] According to one exemplary embodiment of the present disclosure, a plasma processing apparatus and an RF generator capable of efficiently generating an RF signal can be provided.

[0007] FIG. 1 is a diagram for explaining an example of the configuration of a plasma processing system. FIG. 1 is a diagram for explaining an example of the configuration of a plasma processing system. FIG. 2 is a diagram for explaining an RF generator according to a first embodiment. FIG. 3 is a diagram for explaining an RF generator according to the first embodiment. FIG. 4 is a diagram for explaining an RF generator according to the first embodiment. FIG. 5 is a diagram for explaining an RF generator according to the first embodiment. FIG. 6 is a diagram for explaining an RF generator according to the first embodiment. FIG. 7 is a diagram for explaining an RF generator according to the first embodiment. FIG. 8 is a diagram for explaining an RF generator according to a second embodiment. FIG. 9 is a diagram for explaining an RF generator according to another embodiment. FIG. 10 is a diagram for explaining an RF generator according to another embodiment.

[0008] Hereinafter, each embodiment of the present disclosure will be described.

[0009] In one exemplary embodiment, a plasma processing apparatus is provided comprising: a chamber; and an RF generator configured to generate an RF signal to generate a plasma in the chamber, the RF generator including: a DC power supply; a resonant circuit electrically connected to the DC power supply; an isolation circuit electrically connected to the resonant circuit and configured to supply current from the DC power supply to the resonant circuit and prevent transfer of resonant energy from the resonant circuit to the DC power supply; a capacitor electrically connected to an output of the resonant circuit; and a switching circuit electrically connected between a node between the resonant circuit and the isolation circuit and a ground potential and configured to switch between an off state that stops supplying current from the resonant circuit to the ground potential and an on state that supplies current from the resonant circuit to the ground potential, wherein in the off state, resonant energy is stored in the resonant circuit and in the on state, oscillation of an RF signal having a resonant frequency continues between the resonant circuit and the switching circuit.

[0010] In one exemplary embodiment, the DC power supply is configured to vary the output voltage.

[0011] In one exemplary embodiment, the RF generator further comprises a voltage sensor electrically connected to the capacitor, and a voltage controller configured to modify the output voltage of the DC power supply based on an output of the voltage sensor.

[0012] In one exemplary embodiment, the switching circuit is configured to repeat a cycle including a period of an off state and a period of an on state based on a switching frequency.

[0013] In one exemplary embodiment, the switching circuit is configured to vary the switching frequency.

[0014] In one exemplary embodiment, the RF generator further comprises a voltage sensor electrically connected to the capacitor, and a frequency control unit configured to change the switching frequency based on an output of the voltage sensor.

[0015] In one exemplary embodiment, the switching circuit is configured to vary the switching frequency in the range of 10 kHz to 10 MHz.

[0016] In one exemplary embodiment, the switching frequency is less than the resonant frequency of the resonant circuit.

[0017] In one exemplary embodiment, the switching circuit is configured to vary at least one of the length of the off-state period and the length of the on-state period in the cycle.

[0018] In one exemplary embodiment, the RF generator further comprises a voltage sensor electrically connected to the capacitor, and a period control unit configured to change at least one of the length of the off state period and the length of the on state period in the cycle based on an output of the voltage sensor.

[0019] In one exemplary embodiment, the switching circuit is configured to vary the ratio of the length of the off-state period or the length of the on-state period to the period in a range of 1% to 99%.

[0020] In one exemplary embodiment, the resonant circuit includes a variable element, and the resonant frequency is changed by changing a parameter of the variable element.

[0021] In one exemplary embodiment, the RF generator further comprises a drive circuit configured to vary a parameter of the variable element, a voltage sensor electrically connected to the capacitor, and a parameter control unit configured to vary the parameter via the drive circuit based on an output of the voltage sensor.

[0022] In one exemplary embodiment, the resonant circuit is configured to vary the resonant frequency in the range of 10 MHz to 300 MHz.

[0023] In one exemplary embodiment, an RF generator is provided that includes: a DC power supply; a resonant circuit electrically connected to the DC power supply; an isolation circuit electrically connected to the resonant circuit and configured to supply current from the DC power supply to the resonant circuit and to prevent transfer of resonant energy from the resonant circuit to the DC power supply; a capacitor electrically connected to an output of the resonant circuit; and a switching circuit electrically connected between a node between the resonant circuit and the isolation circuit and a ground potential and configured to switch between an off state that stops supplying current from the resonant circuit to the ground potential and an on state that supplies current from the resonant circuit to the ground potential, wherein in the off state resonant energy is stored in the resonant circuit and in the on state oscillation of an RF signal having a resonant frequency continues between the resonant circuit and the switching circuit.

[0024] In one exemplary embodiment, the DC power supply is configured to vary the output voltage.

[0025] In one exemplary embodiment, the switching circuit is configured to repeat a cycle including a period of an off state and a period of an on state based on a switching frequency.

[0026] In one exemplary embodiment, the switching circuit is configured to vary the switching frequency.

[0027] In one exemplary embodiment, the switching circuit is configured to vary at least one of the length of the off-state period and the length of the on-state period in the cycle.

[0028] In one exemplary embodiment, the resonant circuit includes a variable element, and the resonant frequency is changed by changing a parameter of the variable element.

[0029] Hereinafter, each embodiment of the present disclosure will be described in detail with reference to the drawings. In each drawing, the same or similar elements are designated by the same reference numerals, and redundant explanations will be omitted. Unless otherwise specified, the positional relationships, such as up, down, left, and right, will be described based on the positional relationships shown in the drawings. The dimensional ratios in the drawings do not represent actual ratios, and the actual ratios are not limited to the ratios shown in the drawings.

[0030] <Example of Plasma Processing System> FIG. 1 is a diagram illustrating an example of the configuration of a plasma processing system. In one embodiment, the plasma processing system includes a plasma processing apparatus 1 and a control unit 2. The plasma processing system is an example of a substrate processing system, and the plasma processing apparatus 1 is an example of a substrate processing apparatus. The plasma processing apparatus 1 includes a plasma processing chamber 10, a substrate support 11, and a plasma generation unit 12. The plasma processing chamber 10 has a plasma processing space. The plasma processing chamber 10 also 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 a gas supply unit 20 (described later), and the gas exhaust port is connected to an exhaust system 40 (described later). The substrate support 11 is disposed in the plasma processing space and has a substrate support surface for supporting a substrate.

[0031] The plasma generating unit 12 is configured to generate plasma from at least one processing gas supplied into the plasma processing space. The plasma formed in the plasma processing space may be capacitively coupled plasma (CCP), inductively coupled plasma (ICP), electron cyclotron resonance (ECR) plasma, helicon wave plasma (HWP), or surface wave plasma (SWP). Various types of plasma generating units may be used, including alternating current (AC) plasma generating units and direct current (DC) plasma generating units. In one embodiment, the AC signal (AC power) used in the AC plasma generator has a frequency in the range of 100 kHz to 10 GHz. Therefore, AC signals include RF (Radio Frequency) signals and microwave signals. In one embodiment, the RF signal has a frequency in the range of 100 kHz to 300 MHz.

[0032] The control unit 2 processes computer-executable instructions that cause the plasma processing apparatus 1 to perform the various steps described in this disclosure. The control unit 2 may be configured to control each element of the plasma processing apparatus 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 apparatus 1. The control unit 2 is realized by, for example, a computer 2a. The control unit 2 may include a processing unit 2a1, a memory unit 2a2, and a communication interface 2a3. The functions performed by the processing unit 2a1 described in this disclosure may be implemented in circuitry or processing circuitry, including general-purpose processors, application-specific processors, integrated circuits, ASICs (Application Specific Integrated Circuits), CPUs (Central Processing Units), conventional circuitry, and / or combinations thereof, programmed to perform the described functions. A processor is considered to be a circuit or processing circuit including transistors and other circuitry. The processor may also be a programmed processor that executes a program stored in the memory unit 2a2. This program may be stored in the memory unit 2a2 in advance or may be acquired via a medium when needed. The acquired program is stored in the storage unit 2a2 and read from the storage unit 2a2 by the processing unit 2a1 for execution. The medium may be various storage media readable by the computer 2a or a communication line connected to the communication interface 2a3. The storage unit 2a2 may include a random access memory (RAM), a read-only memory (ROM), a hard disk drive (HDD), a solid state drive (SSD), or a combination thereof. The communication interface 2a3 may communicate with the plasma processing apparatus 1 via a communication line such as a local area network (LAN).In this disclosure, a circuit, unit, or means is hardware that is programmed to implement or configured to implement a described function. The hardware may be any hardware described in this disclosure or any hardware that is programmed to implement or known to implement the described function. If the hardware is a processor, which is considered a type of circuit, the circuit, means, or unit is a combination of hardware and software used to configure the hardware and / or processor.

[0033] The following describes a configuration example of a capacitively coupled plasma processing apparatus as an example of the plasma processing apparatus 1. Fig. 2 is a diagram for explaining a configuration example of a capacitively coupled plasma processing apparatus.

[0034] The capacitively coupled plasma processing apparatus 1 includes a plasma processing chamber 10, a gas supply unit 20, a power supply system 30, and an exhaust system 40. The plasma processing apparatus 1 also includes a substrate support 11 and a gas inlet. The gas inlet is configured to introduce at least one process gas into the plasma processing chamber 10. The gas inlet includes a showerhead 13. The substrate support 11 is disposed within the plasma processing chamber 10. The showerhead 13 is disposed above the substrate support 11. In one embodiment, the showerhead 13 forms at least a portion of the ceiling of the plasma processing chamber 10. The plasma processing chamber 10 has a plasma processing space 10s defined by the showerhead 13, a sidewall 10a of the plasma processing chamber 10, and the substrate support 11. The plasma processing chamber 10 is grounded. The showerhead 13 and the substrate support 11 are electrically insulated from the housing of the plasma processing chamber 10.

[0035] The substrate support 11 includes a main body 111 and a ring assembly 112. The main body 111 has a central region 111a for supporting a substrate W and an annular region 111b for supporting the ring assembly 112. A wafer is an example of a substrate W. The annular region 111b of the main body 111 surrounds the central region 111a of the main body 111 in a plan view. The substrate W is disposed on the central region 111a of the main body 111, and the ring assembly 112 is disposed on the annular region 111b of the main body 111 so as to surround the substrate W on the central region 111a of the main body 111. Therefore, the central region 111a is also called a substrate support surface for supporting the substrate W, and the annular region 111b is also called a ring support surface for supporting the ring assembly 112.

[0036] In one embodiment, the main body 111 includes a base 1110 and an electrostatic chuck 1111. The base 1110 includes a conductive member. The conductive member of the base 1110 may function as a lower electrode. The electrostatic chuck 1111 is disposed on the base 1110. The electrostatic chuck 1111 includes a ceramic member 1111a and an electrostatic chuck electrode 1111b disposed within the ceramic member 1111a. The electrostatic chuck electrode 1111b is also referred to as a clamping electrode. In one embodiment, the electrostatic chuck electrode 1111b is electrically connected or coupled to a chuck power supply. The chuck power supply may be a DC power supply or an AC power supply. The ceramic member 1111a has a central region 111a. In one embodiment, the ceramic member 1111a also has an annular region 111b. Note that the annular region 111b may be formed on another member surrounding the electrostatic chuck 1111, such as an annular electrostatic chuck or an annular insulating member. In this case, the ring assembly 112 may be disposed on the annular electrostatic chuck or the annular insulating member, or may be disposed on both the electrostatic chuck 1111 and the annular insulating member. At least one bias electrode electrically connected to or coupled to a power supply 31 and / or a power supply 32 (described later) may be disposed within the ceramic member 1111a. In this case, the at least one bias electrode functions as a lower electrode. Alternatively, the conductive member of the base 1110 and the bias electrode within the ceramic member 1111a may function as multiple lower electrodes. In one embodiment, the first voltage generation unit 32a, which functions as a voltage pulse generation unit (described later), is electrically connected to or coupled to the bias electrode within the ceramic member 1111a, and the first RF generation unit 31a (described later) is electrically connected to or coupled to the conductive member of the base 1110. The electrostatic chuck electrode 1111b may function as a lower electrode. The substrate support 11 therefore comprises at least one bottom electrode.

[0037] The ring assembly 112 includes one or more annular members. In one embodiment, the one or more annular members include one or more edge rings and at least one cover ring. The edge rings are formed of a conductive or insulating material, and the cover rings are formed of an insulating material.

[0038] The substrate support 11 may also include a temperature adjustment module configured to adjust at least one of the electrostatic chuck 1111, the ring assembly 112, and the substrate to a target temperature. The temperature adjustment module may include a heater, a heat transfer medium, a flow passage 1110a, or a combination thereof. A heat transfer fluid such as brine or a gas flows through the flow passage 1110a. In one embodiment, the flow passage 1110a is formed in the base 1110, and one or more heaters are disposed in the ceramic member 1111a of the electrostatic chuck 1111. The substrate support 11 may also include a heat transfer gas supply configured to supply a heat transfer gas to a gap between the backside of the substrate W and the central region 111a.

[0039] The showerhead 13 is configured to introduce at least one process gas from the gas supply unit 20 into the plasma processing space 10s. The showerhead 13 has at least one gas supply port 13a, at least one gas diffusion chamber 13b, and multiple gas inlets 13c. The process gas supplied to the gas supply port 13a passes through the gas diffusion chamber 13b and is introduced into the plasma processing space 10s from the multiple gas inlets 13c. The showerhead 13 also includes at least one upper electrode. In addition to the showerhead 13, the gas inlet may also include one or more side gas injectors (SGIs) attached to one or more openings formed in the sidewall 10a.

[0040] 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 configured to supply at least one process gas from a corresponding gas source 21 to the showerhead 13 via a corresponding flow controller 22. Each flow controller 22 may include, for example, a mass flow controller or a pressure-controlled flow controller. Additionally, the gas supply unit 20 may include at least one flow modulation device that modulates or pulses the flow rate of the at least one process gas.

[0041] The power supply system 30 includes a power supply 31 electrically connected or coupled to the plasma processing chamber 10. In one embodiment, the power supply 31 is electrically connected or coupled to the plasma processing chamber 10 via at least one impedance matcher. The impedance matcher may be a mechanically controlled matcher or an electronically controlled matcher. The power supply 31 is configured to supply at least one RF signal (RF power) to at least one lower electrode and / or at least one upper electrode. This generates plasma from at least one processing gas supplied to the plasma processing space 10s. Therefore, the power supply 31 can function as at least a part of the plasma generation unit 12. Furthermore, by supplying a bias RF signal to the at least one lower electrode, a bias potential is generated on the substrate W, thereby attracting ion components in the formed plasma to the substrate W.

[0042] The power supply 31 includes a first RF generator 31a and a second RF generator 31b. The first RF generator 31a is electrically connected or coupled to at least one lower electrode and / or at least one upper electrode and is configured to generate a source RF signal (source RF power) to generate plasma in the plasma processing space 10s. In one embodiment, the source RF signal has a frequency in the range of 10 MHz to 300 MHz. In one embodiment, the first RF generator 31a may be configured to generate multiple source RF signals having different frequencies. The generated one or more source RF signals are supplied to at least one lower electrode and / or at least one upper electrode.

[0043] The second RF generator 31b is electrically connected or coupled to at least one lower electrode and configured to generate a bias RF signal (bias RF power). In one embodiment, the second RF generator 31b is electrically connected or coupled to at least one lower electrode via at least one impedance matcher. When the first RF generator 31a is electrically connected or coupled to a lower electrode, the second RF generator 31b may be electrically connected or coupled to the same lower electrode or to another lower electrode. The frequency of the bias RF signal may be the same as 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 second RF generator 31b may be configured to generate multiple bias RF signals having different frequencies. The generated one or more bias RF signals are supplied to at least one lower electrode. In various embodiments, at least one of the source RF signal and the bias RF signal may be pulsed.

[0044] The power supply system 30 may also include a power supply 32 electrically connected or coupled to the plasma processing chamber 10. The power supply 32 includes a first voltage generator 32a and a second voltage generator 32b. In one embodiment, the first voltage generator 32a is electrically connected or coupled to at least one lower electrode and configured to generate a first voltage signal. The generated first voltage signal is applied to the at least one lower electrode. In one embodiment, the second voltage generator 32b is electrically connected or coupled to at least one upper electrode and configured to generate a second voltage signal. The generated second voltage signal is applied to the at least one upper electrode.

[0045] In various embodiments, the first and / or second voltage signals may be pulsed. In this case, the first voltage generator 32a and / or the second voltage generator 32b function as a voltage pulse generator configured to generate a sequence of voltage pulses. Thus, the sequence of voltage pulses is applied to at least one lower electrode and / or at least one upper electrode. In one embodiment, the sequence of voltage pulses includes multiple cycles, each cycle including a burst of voltage pulses during a first period and a constant reference voltage during a second period. That is, the bursts of voltage pulses are repeated in the sequence of voltage pulses. The absolute value of the voltage level of the voltage pulses is greater than the absolute value of the voltage level of the reference voltage. The voltage pulses may have an arbitrary waveform, such as a rectangular, trapezoidal, triangular, or combination thereof, and the arbitrary waveform may vary over time. The voltage pulses may have either positive or negative polarity. Furthermore, the sequence of voltage pulses may include one or more positive polarity voltage pulses and one or more negative polarity voltage pulses within one cycle. The first and second voltage generating units 32a and 32b may be provided in addition to the power supply 31, or the first voltage generating unit 32a may be provided instead of the second RF generating unit 31b.

[0046] The exhaust system 40 may be connected to, for example, a gas exhaust port 10e provided at the bottom of the plasma processing chamber 10. The exhaust system 40 may include a pressure regulating valve and a vacuum pump. The pressure in the plasma processing space 10s is regulated by the pressure regulating valve. The vacuum pump may include a turbomolecular pump, a dry pump, or a combination thereof.

[0047] <Example of First RF Generator 31a> Hereinafter, a configuration example of the first RF generator 31a will be described with reference to FIGS.

[0048] 3 is a diagram illustrating an example of the configuration of a first RF generator 31a according to the first embodiment. The first RF generator 31a includes a DC power supply 300, a resonant circuit 302, an isolation circuit 304, a switching circuit 306, and a capacitor 308.

[0049] The DC power supply 300 is an element that applies a constant or slow pulse voltage to other elements. In one example, the DC power supply 300 applies voltage pulses in the range of 0.1 kHz to 50 kHz. The DC power supply 300 can also apply voltage pulses in at least one of on-off operation, high-low operation, and high-low-off operation. In one embodiment, the DC power supply 300 is configured to have a variable output voltage. In one embodiment, the DC power supply 300 applies a negative voltage, but may also apply a positive voltage.

[0050] The resonant circuit 302 is electrically connected to the DC power supply 300 and configured to store resonant energy. In one embodiment, the resonant energy may be electrical energy stored in elements (such as a capacitor and an inductor, for example) that constitute the resonant circuit 302. In one embodiment, the resonant energy may be energy that generates current and voltage resonance when the resonant circuit 302 is in a resonant state, which will be described later. Hereinafter, storing the resonant energy in the resonant circuit 302 may be expressed as "the resonant circuit 302 being charged."

[0051] In one embodiment, the resonant circuit 302 includes a variable element, and is configured so that the resonant frequency can be changed by changing the parameters of the variable element. In one example, the resonant circuit 302 includes a variable inductor and a variable capacitor as variable elements, and is configured so that the inductance of the variable inductor and the capacitance of the variable capacitor can be changed. In one embodiment, the resonant circuit 302 is configured so that the resonant frequency can be changed in the range of 10 MHz to 300 MHz.

[0052] The isolation circuit 304 is electrically connected to the resonant circuit 302 and is configured to supply current from the DC power supply 300 to the resonant circuit 302. The isolation circuit 304 is further configured to block the transmission of resonant energy from the resonant circuit 302 to the DC power supply 300. That is, the isolation circuit 304 is configured to transmit energy one way from the DC power supply 300 to the resonant circuit 302. The isolation circuit 304 can function as a filter that protects the DC power supply 300 from the resonant frequency of the resonant circuit 302. The isolation circuit 304 can also function as a damping element when the DC power supply 300 outputs slow pulses. The isolation circuit 304 can be configured using, for example, an inductor, a resistor, a parallel capacitor, a diode, etc.

[0053] The switching circuit 306 is electrically connected between a node between the resonant circuit 302 and the isolation circuit 304 and ground potential. Note that electrically connecting the switching circuit 306 between the node and ground potential may include connecting elements, circuits, devices, etc. other than the switching circuit 306 between the node and ground potential. The switching circuit 306 may be configured using, for example, an FET, a PIN diode, etc.

[0054] The switching circuit 306 is configured to be switchable between an off state in which the supply of current from the resonant circuit 302 to the ground potential is stopped, and an on state in which the resonant circuit 302 supplies current to the ground potential. Stopping the supply of current from the resonant circuit 302 to the ground potential can also be said to prevent current from flowing from the resonant circuit 302 to the ground potential. Supplying current from the resonant circuit 302 to the ground potential can also be said to allow current to flow from the resonant circuit 302 to the ground potential. As will be described later, when the switching circuit 306 is in the off state, the resonant circuit 302 is charged by the DC power supply 300. On the other hand, when the switching circuit 306 is in the on state, the resonant circuit 302 resonates. Therefore, hereinafter, the off state and the on state will be referred to as the "charging state" and the "resonant state", respectively.

[0055] In one embodiment, the switching circuit 306 repeats a cycle including a period in the charging state and a period in the resonant state (hereinafter referred to as a "switching cycle") based on a switching frequency. In one embodiment, the switching circuit 306 is configured so that the switching frequency is variable. In one embodiment, the switching circuit 306 is configured so that the switching frequency is variable within a range of 10 kHz to 10 MHz.

[0056] In one embodiment, the switching circuit 306 is configured to be able to change at least one of the length of the period of the charging state and the length of the period of the resonant state in a switching period (hereinafter referred to as "switching duty") In one embodiment, the switching circuit 306 is configured to be able to change the ratio of the length of the period of the charging state and / or the length of the period of the resonant state to the switching period in a range of at least 1% to 99%.

[0057] In one embodiment, the switching circuit 306 switches between the charging state and the resonant state based on a first switching period and a second switching period that is shorter than the first switching period. In one embodiment, the switching circuit 306 switches between the charging state and the resonant state based on a first switching duty and a second switching duty that is higher than the first switching duty.

[0058] The capacitor 308 is electrically connected to the output side of the resonant circuit 302. The output side of the resonant circuit 302 may be on the opposite side of the resonant circuit 302 from the side to which the isolation circuit 304 is connected. The capacitor 308 may isolate the output load (in one example, the chamber 10 and the plasma including the sheath oscillation) from the oscillation of the resonant circuit 302. Hereinafter, the "output current" is defined as the current flowing from point A to point B in FIG. 3. The "output voltage" is defined as the potential difference between point A and ground potential.

[0059] The capacitor 308 is configured to supply an RF signal having the resonant frequency of the resonant circuit 302 to the plasma processing chamber 10 when the switching circuit 306 is in a resonant state. That is, by electrically connecting the plasma processing chamber 10 to point B of the capacitor 308, an RF signal can be input to the plasma processing chamber 10. The supplied RF signal may be a sine wave.

[0060] In one embodiment, the capacitor 308 is configured to have a variable capacitance. That is, the capacitor 308 may be a variable capacitor. This configuration allows adjustment of the isolation between the first RF generator 31 a and the plasma processing chamber 10. This configuration also allows the resonant frequency of the resonant circuit 302 to be easily changed. Note that configuring the capacitor 308 to have a variable capacitance is not essential for realizing the function of generating an RF signal and the function of increasing the transmission efficiency of the RF signal to the plasma processing chamber 10.

[0061] Next, an example of the operation of the first RF generating unit 31a according to the first embodiment will be described with reference to FIGS.

[0062] 4A is a conceptual diagram of the circuit of the first RF generating unit 31a when the switching circuit 306 is in a charging state. In this state, the switching circuit 306 is assumed to be open. Opening the switching circuit 306 is an example of stopping the supply of current from the resonant circuit 302 to the ground potential. In the state of FIG. 4A, the DC power supply 300 supplies current to the resonant circuit 302. This charges the resonant circuit 302.

[0063] 4B is a conceptual diagram of the circuit of the first RF generating unit 31a when the switching circuit 306 is in a resonant state. In this state, the switching circuit 306 is short-circuited. The short-circuiting of the switching circuit 306 is an example of a situation in which a current is supplied from the resonant circuit 302 to the ground potential. In the state of FIG. 4B, the resonant circuit 302 passes a current to the ground potential via the switching circuit 306 and generates a resonant current (and a resonant voltage) between the isolation circuit 304 and the capacitor 308.

[0064] 5 shows an example of the output voltage and current when the switching circuit 306 periodically switches between the charging state and the resonant state according to the switching frequency. When the switching circuit 306 is in the charging state (see FIG. 4A), the output voltage changes slowly and the output current is approximately zero. When the switching circuit 306 is in the resonant state (see FIG. 4B), both the output voltage and the output current oscillate at a high frequency. This high frequency corresponds to the resonant frequency of the resonant circuit 302.

[0065] As illustrated in FIG. 5 , the switching frequency is lower than the frequencies of the output voltage and output current when the switching circuit 306 is in a resonant state. That is, the switching frequency is lower than the resonant frequency of the resonant circuit 302. In one example, when the switching frequency is anywhere between 10 kHz and 10 MHz, the resonant frequency is anywhere between 10 MHz and 300 MHz. Note that when the switching frequency fsw can be set (or changed) within the range of fsw1≦fsw≦fsw2 and the resonant frequency fre can be set (or changed) within the range of fre1≦fre≦fre2, the switching frequency being lower than the resonant frequency of the resonant circuit 302 only needs to satisfy fsw<fre, and is not limited to satisfying fsw2<fre1. That is, in a specific circuit or device, if there is at least an instantaneous moment when the switching frequency is lower than the resonant frequency, it can be said that the switching frequency is lower than the resonant frequency of the resonant circuit 302.

[0066] The switching frequency and the resonant frequency can be determined independently of each other. That is, the value of one of the switching frequency and the resonant frequency is not constrained by the value of the other. For example, a designer of the first RF generating unit 31a can determine the switching frequency in the circuit design of the switching circuit 306 and the resonant frequency in the circuit design of the resonant circuit 302 (without being constrained by the previously determined switching frequency). Furthermore, the RF signal generated by the first RF generating unit 31a does not require a matching circuit. That is, the first RF generating unit 31a does not require adjustment to improve the transmission efficiency of the RF signal depending on the state of the plasma processing chamber 10.

[0067] FIG. 6 is a diagram illustrating an example configuration of the resonant circuit 302. The resonant circuit 302 may be configured by an LC circuit, or may be configured using a transformer. FIGS. 6A and 6B are diagrams illustrating an example when the resonant circuit 302 is configured by an LC circuit. The resonant circuit 302 in FIGS. 6A and 6B includes an inductor 3021 and a capacitor 3022. The position of the inductor 3021 differs between FIGS. 6A and 6B. That is, in the example configuration of FIG. 6A, the inductor 3021 is provided on the isolation circuit 304 side with respect to point C, whereas in the example configuration of FIG. 6B, the inductor 3021 is provided on the capacitor 308 side with respect to point C.

[0068] In one embodiment, the inductance of inductor 3021 may be 10 nH to 10 μH. In one embodiment, the capacitance of capacitor 3022 may be 1 pF to 1000 pF. Note that when the resonant frequency to be realized by resonant circuit 302 is determined and one of the inductance of inductor 3021 and the capacitance of capacitor 3022 is already determined, the other can be uniquely determined.

[0069] Fig. 6B is a diagram illustrating an example of a case where a transformer is used to configure the resonant circuit 302. The resonant circuit 302 in Fig. 6B includes a transformer 3023, a capacitor 3024, and a capacitor 3025. The transformer 3023 includes an inductor 3023a and an inductor 3023b.

[0070] The inductance of inductor 3023a and the inductance of inductor 3023b may be 10 nH to 10 μH. The inductance of inductor 3023a and the inductance of inductor 3023b may be the same value or different values. The capacitance of capacitor 3024 and the capacitance of capacitor 3025 may be 1 pF to 1000 pF. The capacitance of capacitor 3024 and the capacitance of capacitor 3025 may be the same value or different values. When the resonant frequency to be realized by resonant circuit 302 is determined and one of (1) the inductance of inductor 3023a and the inductance of inductor 3023b and (2) the capacitance of capacitor 3024 and the capacitance of capacitor 3025 has already been determined, the other can be uniquely determined.

[0071] As illustrated with reference to FIGS. 6-7, resonant circuit 302 can be configured in a variety of ways to achieve the operation described with reference to FIGS. 4-5.

[0072] Second Embodiment Fig. 7 is a diagram for explaining an example of the configuration of a first RF generating unit 31a and a control unit 2 according to a second embodiment. In the following, content that may overlap with the description according to the first embodiment may be omitted. The first RF generating unit 31a according to the second embodiment may further include a voltage sensor 310, a driver circuit 312, and a drive circuit 314 in addition to the configuration that the first RF generating unit 31a according to the first embodiment may include.

[0073] Moreover, the first RF generation unit 31a according to the second embodiment is controlled by the control unit 2. The control unit 2 can function as an acquisition unit 200, a voltage control unit 202, a period control unit 204, a frequency control unit 206, and a parameter control unit 208 by executing a program stored in the storage unit 2a2.

[0074] The voltage sensor 310 is electrically connected to the capacitor 308. In one embodiment, the voltage sensor 310 is configured to measure the output voltage. In one embodiment, the voltage sensor 310 acquires at least one of the amplitude value of the output voltage, the output frequency of the output voltage, the output duty of the output voltage, and the period of the output voltage as a measurement value. In one embodiment, the voltage sensor 310 is configured to be able to communicate with the control unit 2.

[0075] The driver circuit 312 is configured to be able to change the operation of the switching circuit. In one embodiment, the driver circuit 312 is configured to be able to change at least one of the switching frequency, switching duty, and operation timing of the switching circuit. In one embodiment, the driver circuit 312 is configured to be able to communicate with the control unit 2.

[0076] When the resonant circuit 302 includes a variable element, the drive circuit 314 is configured to be able to change the parameter (variable amount) of the variable element. In one embodiment, the drive circuit 314 changes the capacitance of a variable capacitor included in the resonant circuit 302. In one embodiment, the drive circuit 314 changes the inductance of a variable inductor included in the resonant circuit 302. In other words, the drive circuit 314 can change the resonant frequency of the resonant circuit 302. In one embodiment, the drive circuit 314 is configured to be able to communicate with the control unit 2.

[0077] The acquisition unit 200 acquires the measurement value from the voltage sensor 310. The acquisition unit 200 may acquire the measurement value from the voltage sensor 310 sequentially, or may acquire measurement values ​​for a certain period in a batch processing manner.

[0078] The voltage control unit 202 changes the output voltage of the DC power supply 300 based on the measurement value acquired by the acquisition unit 200. In one embodiment, the voltage control unit 202 increases the output voltage of the DC power supply 300 when it determines that the amplitude of the output voltage (an example of a measurement value) does not satisfy, for example, the lower limit of a setting value of a recipe. In another embodiment, the voltage control unit 202 decreases the output voltage of the DC power supply 300 when it determines that the amplitude of the output voltage exceeds, for example, the upper limit of a setting value of a recipe.

[0079] The period control unit 204 changes at least one of the length of the period of the charging state and the length of the period of the resonant state in the switching cycle (i.e., the switching duty) based on the measurement value acquired by the acquisition unit 200. In one embodiment, the period control unit 204 changes the switching duty of the switching circuit 306 via the driver circuit 312. In one embodiment, the period control unit 204 increases the switching duty of the switching circuit 306 when it is determined that the output duty of the output voltage (an example of a measurement value) does not satisfy, for example, a lower limit of a setting value of a recipe. In another embodiment, the period control unit 204 decreases the switching duty of the switching circuit 306 when it is determined that the output duty of the output voltage (an example of a measurement value) exceeds, for example, an upper limit of a setting value of a recipe.

[0080] The frequency control unit 206 changes the switching frequency based on the measurement value acquired by the acquisition unit 200. In one embodiment, the period control unit 204 changes the switching frequency of the switching circuit 306 via the driver circuit 312. In one embodiment, the frequency control unit 206 reduces the switching frequency of the switching circuit 306 (i.e., extends the switching period) when it is determined that the period of the output voltage (an example of a measurement value) does not satisfy, for example, a lower limit of a setting value of a recipe. In another embodiment, the period control unit 204 increases the switching frequency of the switching circuit 306 (i.e., shortens the switching period) when it is determined that the period of the output voltage (an example of a measurement value) exceeds, for example, an upper limit of a setting value of a recipe.

[0081] The parameter control unit 208 changes the parameters of the variable elements of the resonant circuit 302 via the drive circuit 314 based on the measurement values ​​acquired by the acquisition unit 200. In one embodiment, when the parameter control unit 208 determines that the output frequency of the output unit voltage (an example of a measurement value) does not satisfy, for example, a lower limit of a setting value of a recipe, the parameter control unit 208 changes the parameters so that the resonant frequency of the resonant circuit 302 increases. In another embodiment, when the parameter control unit 208 determines that the output frequency of the output unit voltage (an example of a measurement value) exceeds, for example, an upper limit of a setting value of a recipe, the parameter control unit 208 changes the parameters so that the resonant frequency of the resonant circuit 302 decreases.

[0082] <Other Configuration Examples> The configuration of the plasma processing system illustrated in the above embodiment may be modified as appropriate based on the knowledge of a person skilled in the art. For example, at least a portion of the resonant circuit 302 may be located to the right of point B in FIG. 3 . An example of such a configuration will be described with reference to FIG. 8 . The resonant circuit 302 in FIG. 8 is configured with an inductor 3026 and a parasitic capacitance 3027 of a coaxial path. In one embodiment, the parasitic capacitance 3027 may be generated because the path from the first RF generator 31a to the lower electrode of the base 1110 and the path from the second RF generator 31b to the lower electrode are configured as coaxial paths. In one embodiment, the parasitic capacitance 3027 may be generated between the electrode to which the first RF generator 31a is connected (the lower electrode of the base 1110 in the example of FIG. 8 ) and the plasma processing chamber 10. In one embodiment, the parasitic capacitance 3027 may occur in an auxiliary circuit (for example, a filter circuit that protects the second RF generating unit 31b from the RF signal output by the first RF generating unit 31a) provided between the second RF generating unit 31b and the lower electrode of the base 1110. In these cases, the resonant frequency is determined by the relationship between the combined capacitance of the capacitor 308 and the parasitic capacitance 3027 and the inductance of the inductor 3026.

[0083] In the above embodiment, the plasma processing system has been described as including one first RF generator 31 a. However, this is not limiting. The plasma processing system may include multiple first RF generators 31 a. In this case, for example, the frequency of the output current of one first RF generator 31 a (i.e., the resonant frequency of the resonant circuit 302) may be set to f1, and the frequency of the output current of the other first RF generators 31 a may be set to f2 (where f1 ≠ f2) (see FIG. 9 ).

[0084] In the above embodiment, the first RF generating unit 31 a that generates the source RF signal has been described as including the resonant circuit 302. However, the plasma processing system may further include another RF generator that generates the source RF signal without using the resonant circuit 302. The other RF generator may generate the source RF signal by an HF power supply, a DC pulse power supply, and a matching circuit.

[0085] In the above embodiment, the plasma processing apparatus 1 has been described as a capacitively coupled plasma processing apparatus, but is not limited to this. The first RF generating unit 31 a may be implemented in an inductively coupled plasma processing apparatus. When the plasma processing apparatus 1 is an inductively coupled plasma processing apparatus, the first RF generating unit 31 a may be used to supply an RF signal to the upper coil.

[0086] The present disclosure may include the following features.

[0087] a switching circuit electrically connected between a node between the resonant circuit and the isolation circuit and a ground potential, the switching circuit being configured to switch between an off state in which the supply of current from the resonant circuit to the ground potential is stopped and an on state in which current is supplied from the resonant circuit to the ground potential, wherein resonance energy is stored in the resonant circuit in the off state and an RF signal having a resonance frequency is continuously oscillated between the resonant circuit and the switching circuit in the on state.

[0088] [Supplementary Note 2] The plasma processing apparatus of Supplementary Note 1, wherein the DC power supply is configured to change its output voltage.

[0089] [Supplementary Note 3] The plasma processing apparatus according to Supplementary Note 2, wherein the RF generator further includes: a voltage sensor electrically connected to the capacitor; and a voltage control unit configured to change the output voltage of the DC power supply based on an output of the voltage sensor.

[0090] [Supplementary Note 4] The plasma processing apparatus according to any one of Supplementary Note 1 to Supplementary Note 3, wherein the switching circuit is configured to repeat a cycle including a period of the off state and a period of the on state based on a switching frequency.

[0091] [Supplementary Note 5] The plasma processing apparatus according to Supplementary Note 4, wherein the switching circuit is configured to change the switching frequency.

[0092] [Supplementary Note 6] The plasma processing apparatus according to Supplementary Note 5, wherein the RF generator further comprises: a voltage sensor electrically connected to the capacitor; and a frequency control unit configured to change the switching frequency based on an output of the voltage sensor.

[0093] [Supplementary Note 7] The plasma processing apparatus according to Supplementary Note 5 or 6, wherein the switching circuit is configured to change the switching frequency within a range of 10 kHz to 10 MHz.

[0094] [Supplementary Note 8] The plasma processing apparatus according to any one of Supplementary Notes 4 to 7, wherein the switching frequency is lower than a resonant frequency of the resonant circuit.

[0095] [Supplementary Note 9] The plasma processing apparatus according to any one of Supplementary Notes 4 to 8, wherein the switching circuit is configured to change at least one of a length of a period of the off state and a length of a period of the on state in the cycle.

[0096] [Supplementary Note 10] The plasma processing apparatus according to Supplementary Note 9, wherein the RF generator further comprises: a voltage sensor electrically connected to the capacitor; and a period control unit configured to change at least one of a length of the off-state period and a length of the on-state period in the cycle based on an output of the voltage sensor.

[0097] [Supplementary Note 11] The plasma processing apparatus according to Supplementary Note 9 or 10, wherein the switching circuit is configured to change a ratio of the length of the off-state period or the length of the on-state period to the cycle in a range of 1% to 99%.

[0098] [Supplementary Note 12] The plasma processing apparatus according to any one of Supplementary Notes 1 to 11, wherein the resonant circuit includes a variable element, and the resonant frequency is changed by changing a parameter of the variable element.

[0099] [Supplementary Note 13] The plasma processing apparatus according to Supplementary Note 12, wherein the RF generator further comprises: a drive circuit configured to change a parameter of the variable element; a voltage sensor electrically connected to the capacitor; and a parameter control unit configured to change the parameter via the drive circuit based on an output of the voltage sensor.

[0100] [Supplementary Note 14] The plasma processing apparatus according to Supplementary Note 12 or 13, wherein the resonant circuit is configured to change the resonant frequency within a range of 10 MHz to 300 MHz.

[0101] [Supplementary Note 15] An RF generator comprising: a DC power supply; a resonant circuit electrically connected to the DC power supply; an isolation circuit electrically connected to the resonant circuit and configured to supply current from the DC power supply to the resonant circuit and block transmission of resonant energy from the resonant circuit to the DC power supply; a capacitor electrically connected to an output of the resonant circuit; and a switching circuit electrically connected between a node between the resonant circuit and the isolation circuit and a ground potential and configured to switch between an off state in which supply of current from the resonant circuit to the ground potential is stopped and an on state in which current is supplied from the resonant circuit to the ground potential, wherein resonant energy is stored in the resonant circuit in the off state and oscillation of an RF signal having a resonant frequency continues between the resonant circuit and the switching circuit in the on state.

[0102] 16. The RF generator of claim 15, wherein the DC power supply is configured to vary the output voltage.

[0103] [Supplementary Note 17] The RF generator according to Supplementary Note 15 or 16, wherein the switching circuit is configured to repeat a cycle including a period of the off state and a period of the on state based on a switching frequency.

[0104] 18. The RF generator of claim 17, wherein the switching circuit is configured to vary the switching frequency.

[0105] [Supplementary Note 19] The RF generator of Supplementary Note 17 or 18, wherein the switching circuit is configured to change at least one of a length of a period of the off state and a length of a period of the on state in the period.

[0106] [Supplementary Note 20] The RF generator of any one of Supplementary Notes 15 to 19, wherein the resonant circuit includes a variable element, and the resonant frequency is changed by changing a parameter of the variable element.

[0107] REFERENCE SIGNS LIST 1: Plasma processing apparatus, 2: Control unit, 31a: First RF generating unit, 31b: Second RF generating unit, 200: Acquisition unit, 202: Voltage control unit, 204: Period control unit, 206: Frequency control unit, 208: Parameter control unit, 300: DC power supply, 302: Resonance circuit, 304: Isolation circuit, 306: Switching circuit, 308: Capacitor, 310: Voltage sensor, 312: Driver circuit, 314: Drive circuit

Claims

1. A plasma processing apparatus comprising: a chamber; and an RF generator configured to generate an RF signal to generate plasma in the chamber, the RF generator including: a DC power supply; a resonant circuit electrically connected to the DC power supply; an isolation circuit electrically connected to the resonant circuit and configured to supply current from the DC power supply to the resonant circuit and prevent transfer of resonant energy from the resonant circuit to the DC power supply; a capacitor electrically connected to an output of the resonant circuit; and a switching circuit electrically connected between a node between the resonant circuit and the isolation circuit and a ground potential and configured to switch between an off state in which supply of current from the resonant circuit to the ground potential is stopped and an on state in which current is supplied from the resonant circuit to the ground potential, wherein resonant energy is stored in the resonant circuit in the off state and an RF signal having a resonant frequency continues to oscillate between the resonant circuit and the switching circuit in the on state.

2. The plasma processing apparatus of claim 1, wherein the DC power supply is configured to vary the output voltage.

3. The plasma processing apparatus of claim 2, wherein the RF generator further comprises: a voltage sensor electrically connected to the capacitor; and a voltage control unit configured to change the output voltage of the DC power supply based on an output of the voltage sensor.

4. The plasma processing apparatus according to claim 1, wherein the switching circuit is configured to repeat a cycle including a period of the off state and a period of the on state based on a switching frequency.

5. The plasma processing apparatus of claim 4, wherein the switching circuit is configured to vary the switching frequency.

6. The plasma processing apparatus of claim 5, wherein the RF generator further comprises: a voltage sensor electrically connected to the capacitor; and a frequency control unit configured to change the switching frequency based on an output of the voltage sensor.

7. The plasma processing apparatus of claim 5, wherein the switching circuit is configured to vary the switching frequency in a range of 10 kHz to 10 MHz.

8. The plasma processing apparatus according to claim 4, wherein the switching frequency is lower than the resonant frequency of the resonant circuit.

9. The plasma processing apparatus according to claim 4, wherein the switching circuit is configured to change at least one of the length of the off-state period and the length of the on-state period in the cycle.

10. The plasma processing apparatus of claim 9, wherein the RF generator further comprises: a voltage sensor electrically connected to the capacitor; and a period control unit configured to change at least one of the length of the off-state period and the length of the on-state period in the cycle based on the output of the voltage sensor.

11. The plasma processing apparatus according to claim 9, wherein the switching circuit is configured to change the ratio of the length of the off-state period or the length of the on-state period to the cycle in a range of 1% to 99%.

12. The plasma processing apparatus of claim 1, wherein the resonant circuit includes a variable element, and the resonant frequency is changed by changing a parameter of the variable element.

13. The plasma processing apparatus of claim 12, wherein the RF generator further comprises: a drive circuit configured to change a parameter of the variable element; a voltage sensor electrically connected to the capacitor; and a parameter control unit configured to change the parameter via the drive circuit based on an output of the voltage sensor.

14. The plasma processing apparatus of claim 12, wherein the resonant circuit is configured to vary the resonant frequency in the range of 10 MHz to 300 MHz.

15. An RF generator comprising: a DC power supply; a resonant circuit electrically connected to the DC power supply; an isolation circuit electrically connected to the resonant circuit and configured to supply current from the DC power supply to the resonant circuit and block transmission of resonant energy from the resonant circuit to the DC power supply; a capacitor electrically connected to an output of the resonant circuit; and a switching circuit electrically connected between a node between the resonant circuit and the isolation circuit and a ground potential and configured to switch between an off state in which supply of current from the resonant circuit to the ground potential is stopped and an on state in which current is supplied from the resonant circuit to the ground potential, wherein resonant energy is stored in the resonant circuit in the off state and an RF signal having a resonant frequency continues to oscillate between the resonant circuit and the switching circuit in the on state.

16. The RF generator of claim 15, wherein the DC power supply is configured to vary the output voltage.

17. The RF generator of claim 15, wherein the switching circuit is configured to repeat a cycle including a period of the off state and a period of the on state based on a switching frequency.

18. The RF generator of claim 17, wherein the switching circuit is configured to vary the switching frequency.

19. The RF generator of claim 17, wherein the switching circuitry is configured to vary at least one of a length of a period of the off state and a length of a period of the on state in the period.

20. The RF generator of claim 15, wherein the resonant circuit includes a variable element, and the resonant frequency is changed by changing a parameter of the variable element.

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