Plasma processing device, power supply system, and frequency control method

Abstract

The disclosed plasma processing device includes a chamber, a substrate support, and an RF power supply. The substrate support is disposed in the chamber. The RF power supply is configured to supply a source RF signal to a high-frequency electrode to generate plasma from a gas in the chamber. The RF power supply is configured to vary a source frequency of the source RF signal in response to a degree of reflection of the source RF signal from a load thereof so as to reduce the degree of reflection. The RF power supply is configured to vary the source frequency such that the source RF signal does not have a source frequency that generates an unwanted signal that includes a harmonic signal and / or intermodulation distortion relative to the source RF signal and that has a signal level that is large enough not to satisfy a tolerance condition.

Description

Plasma Processing Apparatus, Power Supply System, and Frequency Control Method

[0001] Exemplary embodiments of the present disclosure relate to a plasma processing apparatus, a power supply system, and a frequency control method.

[0002] The plasma processing apparatus is used in plasma processing of a substrate. In the plasma processing apparatus, bias high-frequency power is used to draw ions from the plasma generated in the chamber to the substrate. Patent Document 1 below discloses a plasma processing apparatus that modulates the power level and frequency of the bias high-frequency power.

[0003] Japanese Patent Application Laid-Open No. 2009-246091

[0004] The present disclosure provides a technique for enhancing the stability of a process and reducing the degree of reflection of a source RF signal in a plasma processing apparatus.

[0005] In one exemplary embodiment, a plasma processing apparatus is disclosed. The plasma processing apparatus includes a chamber, a substrate support, and an RF power supply. The substrate support is disposed in the chamber. The RF power supply is configured to supply a source RF signal to a high-frequency electrode to generate plasma from a gas in the chamber. The RF power supply is configured to change the source frequency of the source RF signal according to the degree of reflection so as to reduce the degree of reflection of the source RF signal from its load. The RF power supply is configured to change the source frequency so that the source RF signal does not have a source frequency that generates an unwanted signal including a harmonic signal and / or an intermodulation distortion with respect to the source RF signal and having a signal level that does not satisfy the allowable conditions.

[0006] According to one exemplary embodiment, it is possible to enhance the stability of a process and reduce the degree of reflection of a source RF signal in a plasma processing apparatus.

[0007] This is a diagram illustrating an example configuration of a plasma processing system. This is a diagram illustrating an example configuration of a capacitively coupled plasma processing apparatus. This is a diagram of a plasma processing apparatus according to one exemplary embodiment. This is a diagram of an example of a matching circuit. This is a diagram of an example of an electrical bias waveform. Figures 6(a) and 6(b) are timing charts of an example of a source RF signal and electrical bias in a plasma processing apparatus according to one exemplary embodiment. This is a flowchart showing a frequency control method according to one exemplary embodiment. This is a flowchart showing an example of process STa in a frequency control method according to one exemplary embodiment. This is a block diagram of a computer (a type of circuit) capable of realizing the various control modes described herein.

[0008] Various exemplary embodiments will be described in detail below with reference to the drawings. In each drawing, the same or corresponding parts will be denoted by the same reference numerals.

[0009] Figure 1 is a diagram illustrating an example 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 unit 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 outlet for discharging gas from the plasma processing space. The gas supply port is connected to a gas supply unit 20, which will be described later, and the gas outlet is connected to an exhaust system 40, which will be described later. The substrate support unit 11 is located in the plasma processing space and has a substrate support surface for supporting a substrate.

[0010] The plasma generation 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), ECR (Electron Cyclotron Resonance) plasma, helicon wave excited plasma (HWP), or surface wave plasma (SWP), etc. Various types of plasma generation units, including AC (Alternating Current) plasma generation units and DC (Direct Current) plasma generation units, may also be used. In one embodiment, the AC signal (AC power) used in the AC plasma generation unit has a frequency in the range of 100 kHz to 10 GHz. Therefore, the AC signal includes an RF (Radio Frequency) signal and a microwave signal. In one embodiment, the RF signal has a frequency in the range of 100 kHz to 150 MHz.

[0011] The control unit 2 processes computer-executable instructions that cause the plasma processing apparatus 1 to perform the various processes described herein. The control unit 2 may be configured to control the elements of the plasma processing apparatus 1 to perform the various processes 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 implemented, for example, by a computer 2a. The control unit 2 may include a processing unit 2a1, a storage unit 2a2, and a communication interface 2a3. The functions realized by the processing unit 2a1 described herein may be implemented in a circuit or processing circuit, including a general-purpose processor, an application-specific processor, integrated circuits, ASICs (Application Specific Integrated Circuits), a CPU (Central Processing Unit), a conventional circuit, and / or a combination thereof, programmed to realize the described functions. The processor is considered to be a circuit or processing circuit, including transistors and other circuits. The processor may be a programmed processor that executes a program stored in the storage unit 2a2. This program may be pre-stored in the storage unit 2a2 or retrieved via a medium when needed. The acquired program is stored in the storage unit 2a2 and read from the storage unit 2a2 and executed by the processing unit 2a1. The medium may be various storage media readable by the computer 2a, or it may be a communication line connected to the communication interface 2a3. The storage unit 2a2 may include RAM (Random Access Memory), ROM (Read Only Memory), HDD (Hard Disk Drive), SSD (Solid State Drive), or a combination thereof. The communication interface 2a3 may communicate with the plasma processing device 1 via a communication line such as a LAN (Local Area Network).In this disclosure, circuits, units, and means are hardware programmed to perform or configured to perform the functions described. Such hardware may be any hardware described in this disclosure, or any hardware known to be programmed to perform or execute the functions described. If such hardware is a processor that is considered to be a type of circuit, such circuit, means, or unit is a combination of hardware and software used to constitute such hardware and / or processor.

[0012] The following describes an example configuration of a capacitively coupled plasma processing apparatus as an example of a plasma processing apparatus 1. Figure 2 is a diagram illustrating an example configuration of a capacitively coupled plasma processing apparatus.

[0013] 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 unit 11 and a gas introduction unit. The gas introduction unit is configured to introduce at least one processing gas into the plasma processing chamber 10. The gas introduction unit includes a shower head 13. The substrate support unit 11 is located inside the plasma processing chamber 10. The shower head 13 is located above the substrate support unit 11. In one embodiment, the shower head 13 constitutes 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 shower head 13, the side walls 10a of the plasma processing chamber 10, and the substrate support unit 11. The plasma processing chamber 10 is grounded. The shower head 13 and the substrate support unit 11 are electrically insulated from the housing of the plasma processing chamber 10.

[0014] The substrate support portion 11 includes a main body portion 111 and a ring assembly 112. The main body portion 111 has a central region 111a for supporting the 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 portion 111 surrounds the central region 111a of the main body portion 111 in a plan view. The substrate W is placed on the central region 111a of the main body portion 111, and the ring assembly 112 is placed on the annular region 111b of the main body portion 111 so as to surround the substrate W on the central region 111a of the main body portion 111. Therefore, the central region 111a is also called the substrate support surface for supporting the substrate W, and the annular region 111b is also called the ring support surface for supporting the ring assembly 112.

[0015] 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 can function as a lower electrode. The electrostatic chuck 1111 is placed on the base 1110. The electrostatic chuck 1111 includes a ceramic member 1111a and an electrostatic chuck electrode 1111b placed within the ceramic member 1111a. The electrostatic chuck electrode 1111b is also called 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. Furthermore, other members surrounding the electrostatic chuck 1111, such as an annular electrostatic chuck or an annular insulating member, may have an annular region 111b. In this case, the ring assembly 112 may be placed on the annular electrostatic chuck or the annular insulating member, or it may be placed on both the electrostatic chuck 1111 and the annular insulating member. In addition, at least one bias electrode, which is electrically connected or coupled to the power supply 31 and / or power supply 32 described later, may be placed inside the ceramic member 1111a. In this case, at least one bias electrode functions as a lower electrode. Also, the conductive member of the base 1110 and the bias electrode inside 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 or coupled to the bias electrode inside the ceramic member 1111a, and the first RF generation unit 31a, described later, is electrically connected or coupled to the conductive member of the base 1110. Furthermore, the electrostatic chuck electrode 1111b may function as a lower electrode. Therefore, the substrate support portion 11 includes at least one lower electrode.

[0016] 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 covering ring. The edge rings are formed of a conductive or insulating material, and the covering rings are formed of an insulating material.

[0017] The substrate support section 11 may also include a temperature control 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 control module may include a heater, a heat transfer medium, a flow path 1110a, or a combination thereof. A heat transfer fluid such as brine or gas flows through the flow path 1110a. In one embodiment, the flow path 1110a is formed within the base 1110, and one or more heaters are arranged within the ceramic member 1111a of the electrostatic chuck 1111. The substrate support section 11 may also include a heat transfer gas supply section configured to supply heat transfer gas to the gap between the back surface of the substrate W and the central region 111a.

[0018] The showerhead 13 is configured to introduce at least one processing 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 a plurality of gas inlet ports 13c. The processing gas supplied to the gas supply port 13a passes through the gas diffusion chamber 13b and is introduced into the plasma processing space 10s through the plurality of gas inlet ports 13c. The showerhead 13 also includes at least one upper electrode. In addition to the showerhead 13, the gas introduction unit may also include one or more side gas injectors (SGIs) attached to one or more openings formed in the side wall 10a.

[0019] 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 processing gas to the shower head 13 from a corresponding gas source 21 via a corresponding flow controller 22. Each flow controller 22 may include, for example, a mass flow controller or a pressure-controlled flow controller. Furthermore, the gas supply unit 20 may include at least one flow modulation device that modulates or pulses the flow rate of at least one processing gas.

[0020] The power supply system 30 includes a power supply 31 that is electrically connected to or coupled to the plasma processing chamber 10. In one embodiment, the power supply 31 is electrically connected to 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 part of the plasma generation unit 12. In addition, by supplying a bias RF signal to at least one lower electrode, a bias potential is generated on the substrate W, and ionic components in the formed plasma can be drawn into the substrate W.

[0021] The power supply 31 includes a first RF generation unit 31a and a second RF generation unit 31b. The first RF generation unit 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 first RF generation unit 31a is electrically connected or coupled to at least one lower electrode and / or at least one upper electrode via at least one impedance matcher. In one embodiment, the source RF signal has a frequency in the range of 10 MHz to 150 MHz. In one embodiment, the first RF generation unit 31a may be configured to generate a plurality of source RF signals having different frequencies. One or more generated source RF signals are supplied to at least one lower electrode and / or at least one upper electrode.

[0022] The second RF generation unit 31b is electrically connected to or coupled to at least one lower electrode and is configured to generate a bias RF signal (bias RF power). In one embodiment, the second RF generation unit 31b is electrically connected to or coupled to at least one lower electrode via at least one impedance matcher. When the first RF generation unit 31a is electrically connected to or coupled to a lower electrode, the second RF generation unit 31b may be electrically connected to or coupled to the same lower electrode, or it may be electrically connected to or coupled to a different 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 generation unit 31b may be configured to generate a plurality of 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.

[0023] The power supply system 30 may also include a power supply 32 that is electrically connected to or coupled to the plasma processing chamber 10. The power supply 32 includes a first voltage generation unit 32a and a second voltage generation unit 32b. In one embodiment, the first voltage generation unit 32a is electrically connected to or coupled to at least one lower electrode and is configured to generate a first voltage signal. The generated first voltage signal is applied to at least one lower electrode. In one embodiment, the second voltage generation unit 32b is electrically connected to or coupled to at least one upper electrode and is configured to generate a second voltage signal. The generated second voltage signal is applied to at least one upper electrode.

[0024] In various embodiments, the first and / or second voltage signals may be pulsed. In this case, the first voltage generation unit 32a and / or the second voltage generation unit 32b function as voltage pulse generation units 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 has a plurality of cycles, each cycle including a burst of voltage pulses in a first period and a constant reference voltage in a second period. That is, in the sequence of voltage pulses, the burst of voltage pulses is repeated. The absolute value of the voltage level of the voltage pulse is greater than the absolute value of the voltage level of the reference voltage. The voltage pulse may have an arbitrary waveform having a rectangle, trapezoid, triangle, or a combination thereof, and the arbitrary waveform may change over time. The voltage pulse may have positive polarity or negative polarity. The sequence of voltage pulses may also include one or more positive voltage pulses and one or more negative voltage pulses within one cycle. The first and second voltage generation units 32a and 32b may be provided in addition to the power supply 31, and the first voltage generation unit 32a may be provided in place of the second RF generation unit 31b.

[0025] The exhaust system 40 may be connected to, for example, a gas outlet 10e located 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 regulating valve regulates the pressure in the plasma processing space 10s. The vacuum pump may include a turbomolecular pump, a dry pump, or a combination thereof.

[0026] The following refers to Figure 3. Figure 3 is a diagram showing a plasma processing apparatus according to one exemplary embodiment. As shown in Figure 3, the plasma processing apparatus 1 includes a power supply system 50 used as the power supply system 30 described above. The power supply system 50 includes an RF power supply 51. The power supply system 50 may further include a bias power supply 52. ​​The power supply system 50 may further include a control unit 50c. The power supply system 50 may further include at least one sensor, such as a sensor 55 or a sensor 56. The power supply system 50 may also further include an analyzer 58.

[0027] The RF power supply 51 includes the first RF generation unit 31a described above. The RF power supply 51 is configured to supply a source RF signal HF (source high-frequency power) to generate plasma from gas in the chamber 10. The source RF signal HF has a source frequency fs. That is, the source RF signal HF has a sinusoidal waveform whose frequency (oscillation frequency) is the source frequency fs. The source frequency fs may be in the range of 10 MHz to 150 MHz.

[0028] The RF power supply 51 is electrically connected to the high-frequency electrode via a matching unit 53 and is configured to supply a source RF signal HF to the high-frequency electrode. The high-frequency electrode may be provided within the substrate support 11. The high-frequency electrode may be at least one electrode provided within the conductive member or ceramic member 1111a of the base 1110. Alternatively, the high-frequency electrode may be an upper electrode. When the source RF signal HF is supplied to the high-frequency electrode, plasma is generated from the gas in the chamber 10.

[0029] The matching circuit 53 has a variable impedance. The variable impedance of the matching circuit 53 is set to reduce reflection of the source RF signal HF from the load. The matching circuit 53 can be controlled, for example, by the control unit 50c. The control unit 50c may be the control unit 2, or it may be a separate control circuit from the control unit 2, which is part of the power supply system 50. Alternatively, the control unit 50c may be part of the RF power supply 51.

[0030] In one embodiment, the matching circuit 53 may include a variable capacitor 531 and a variable capacitor 532. One end of the variable capacitor 531 is connected to an electrical path that electrically connects the RF power supply 51 and the high-frequency electrode to each other. The other end of the variable capacitor 531 is connected to ground. The variable capacitor 532 is connected between the RF power supply 51 and the high-frequency electrode. Specifically, one end of the variable capacitor 532 is electrically connected to the RF power supply 51, and the other end of the variable capacitor 532 is electrically connected to the high-frequency electrode.

[0031] The variable capacitor 531 and / or the variable capacitor 532 may be mechanically controlled capacitors. Alternatively, the variable capacitor 531 and / or the variable capacitor 532 may be electronically controlled capacitors. Figure 4 shows an example of a matching circuit. In the example in Figure 4, the variable capacitor 532 is configured as an electronically controlled capacitor. In an electronically controlled variable capacitor, such as the variable capacitor 532 shown in Figure 4, multiple series circuits, each including a series connection of a capacitor and a switch, are connected in parallel. The capacitance of the electronically controlled variable capacitor 532 can be changed by switching the switches of the multiple series circuits ON and OFF (i.e., open and closed).

[0032] Returning to Figure 3, the bias power supply 52 is electrically coupled to the substrate support 11. The bias power supply 52 is electrically connected to the bias electrode in the substrate support 11. The bias electrode may be at least one electrode provided in the conductive member or ceramic member 1111a of the base 1110. The bias electrode may be common with the high-frequency electrode. The bias power supply 52 is configured to periodically supply an electrical bias EB to the bias electrode in order to draw ions from the plasma in the chamber 10 to the substrate W on the substrate support 11. The bias power supply 52 includes the second RF generation unit 31b or the first voltage generation unit 32a described above.

[0033] The following references are made to Figure 5 in conjunction with Figure 3. Figure 5 shows an example of an electrical bias waveform. The bias power supply 52 is configured to periodically supply an electrical bias EB having a waveform period Cb to the bias electrode. That is, the electrical bias EB is applied to the bias electrode in each of a plurality of waveform periods Cb, which are repetitions of the waveform period Cb. The waveform period Cb is defined by the bias frequency. The bias frequency is, for example, a frequency between 50 kHz and 27 MHz. The time length of the waveform period Cb is the reciprocal of the bias frequency. The bias frequency may be 13.56 MHz or less or 400 kHz or less.

[0034] The electrical bias EB may be a bias RF signal generated by the second RF generation unit 31b, i.e., a bias RF signal LF (bias high-frequency power) having a bias frequency. That is, the electrical bias EB may have a sinusoidal waveform whose frequency (oscillation frequency) is the bias frequency. In this case, the bias power supply 52 is electrically connected to the bias electrode via the matching unit 54. The variable impedance of the matching unit 54 is set to reduce the reflection of the bias RF signal LF from the load.

[0035] Alternatively, the electrical bias EB may include a voltage pulse VP generated by the first voltage generation unit 32a. The voltage pulse VP is applied to the bias electrode during a waveform period Cb. The voltage pulse VP is applied to the bias electrode periodically at time intervals equal to the length of the waveform period Cb. That is, a sequence of voltage pulses VP is applied to the bias electrode. The waveform of the voltage pulse VP may be a square wave, a triangular wave, or any other waveform. The polarity of the voltage of the voltage pulse VP is set so that a potential difference is created between the substrate W and the plasma, thereby attracting ions from the plasma to the substrate W. The voltage pulse VP is applied to the bias electrode such that the waveform period Cb includes a period during which the potential of the substrate W is negative. The voltage pulse VP applied to the bias electrode may have a negative potential, a positive potential, or a potential that varies between a positive and a negative potential. The voltage pulse VP may be a pulse of a negative voltage or a pulse of a negative DC voltage. Furthermore, if the electrical bias EB is a voltage pulse VP, the plasma processing apparatus 1 does not need to be equipped with a matching unit 54.

[0036] Hereinafter, Figures 6(a) and 6(b) will be referenced together with Figures 3 and 5. Figures 6(a) and 6(b) are timing charts of an example of a source RF signal and electrical bias in a plasma processing apparatus according to one exemplary embodiment. In these figures, "ON" for the source RF signal HF indicates that the source RF signal HF is being supplied, and "OFF" for the source RF signal HF indicates that the supply of the source RF signal HF has been stopped. In Figure 6(b), "HIGH" for the source RF signal HF indicates that a source RF signal HF with a power level higher than the power level (signal level) indicated by "LOW" is being supplied. In these figures, "ON" for the electrical bias EB indicates that the electrical bias EB is being supplied, and "OFF" for the electrical bias EB indicates that the supply of the electrical bias EB has been stopped. In Figure 6(b), "HIGH" for the electrical bias EB indicates that an electrical bias EB with a higher level than the level indicated by "LOW" is being supplied. Note that if the electrical bias EB is the bias RF signal LF, the level of the electrical bias EB is the power level of the bias RF signal LF. If the electrical bias EB includes a voltage pulse VP, the level of the electrical bias EB increases as the energy of the ions attracted to the substrate W increases. If the electrical bias EB includes a voltage pulse VP, the level of the electrical bias EB may also be the absolute value of the negative voltage level of the voltage pulse VP relative to a reference voltage (e.g., 0V).

[0037] The RF power supply 51 is configured to supply the source RF signal HF in parallel with the periodic supply of the electrical bias EB from the bias power supply 52. ​​As shown in Figure 6(a), the electrical bias EB and the source RF signal HF may be supplied simultaneously and continuously from the start to the end of the process or operation. That is, a continuous wave of the electrical bias EB and a continuous wave of the source RF signal HF may be supplied in parallel.

[0038] Alternatively, as shown in Figure 6(b), the pulses of the electrical bias EB and the source RF signal HF may be supplied periodically at a pulse period Cp (pulse generation period). In this case, the pulses of the electrical bias EB and the source RF signal HF may be supplied synchronously with each other during the pulse period PP within each pulse period Cp. That is, each of the pulse periods PP of multiple pulse periods Cp (in Figure 6(b), the pulse period PP) １ , PP ２ , PP ３ In the above, the pulses of the electrical bias EB and the pulses of the source RF signal HF may be supplied simultaneously. Each pulse period PP includes multiple waveform periods Cb. That is, the electrical bias EB is supplied periodically during each pulse period PP. The pulses of the electrical bias EB may be ON / OFF pulses that alternate between a supply state (ON state in Figure 6(b)) and a stop state (OFF state in Figure 6(b)). Alternatively, the pulses of the electrical bias EB may be HIGH / LOW pulses that alternate between a high level state (HIGH state in Figure 6(b)) and a low level state (LOW state in Figure 6(b)). Furthermore, the pulses of the source RF signal HF may be ON / OFF pulses that alternate between a supply state (ON state in Figure 6(b)) and a stop state (OFF state in Figure 6(b)). Alternatively, the pulse of the source RF signal HF may be a HIGH / LOW pulse that alternates between a high-level state (HIGH state in Figure 6(b)) and a low-level state (LOW state in Figure 6(b)). Furthermore, the power level of the source RF signal HF may be modulated during the period when the source RF signal HF is ON. Furthermore, the power level of the source RF signal HF may be modulated during the period when the power level of the source RF signal HF is HIGH. Furthermore, the power level of the source RF signal HF may be modulated during the period when the power level of the source RF signal HF is LOW.

[0039] Returning to Figure 3, sensor 55 is a VI sensor (voltage / current measuring sensor) configured to measure the voltage and current of the source RF signal HF and output a voltage signal representing the voltage and a current signal representing the current. Sensor 56 is a directional coupler configured to measure the traveling wave and reflected wave of the source RF signal HF and output a traveling wave signal representing the traveling wave and a reflected wave signal representing the reflected wave. The voltage signal and current signal from sensor 55 and the traveling wave signal and reflected wave signal from sensor 56 are input to the control unit 50c.

[0040] The RF power supply 51 is configured to change the source frequency of the source RF signal according to the degree of reflection, in order to reduce the degree of reflection of the source RF signal HF from the load of the RF power supply 51 during the plasma processing period. The plasma processing period is the period during which plasma processing is performed on the substrate on the substrate support 11.

[0041] The degree of reflection may be determined from the phase difference between the voltage and current of the source RF signal HF, or from the difference between the load impedance and a predetermined impedance (e.g., 50Ω). The phase difference between the voltage and current of the source RF signal HF and the difference between the load impedance and the predetermined impedance may be determined in the control unit 50c or RF power supply 51 using the voltage and current signals from the sensor 55. Alternatively, the degree of reflection may be determined from the power of the reflected wave of the source RF signal HF, or from the ratio of the power of the reflected wave to the power of the forward wave (i.e., reflectivity). The power and reflectivity of the reflected wave of the source RF signal HF may be determined in the control unit 50c or RF power supply 51 using the forward wave signal and reflected wave signal from the sensor 56.

[0042] In one embodiment, each of the sensors 55 and 56 may have frequency characteristics whose measurement results depend on the source frequency fs. In this case, the control unit 50c may obtain a corrected voltage signal and a corrected current signal by multiplying each of the voltage signal and current signal from the sensor 55 by a correction coefficient corresponding to the source frequency fs or by adding a correction amount corresponding to the source frequency fs. The degree of reflection may be determined from the corrected voltage signal and the corrected current signal. Alternatively, the control unit 50c may obtain a corrected traveling wave signal and a corrected reflected wave signal by multiplying each of the traveling wave signal and reflected wave signal from the sensor 56 by a correction coefficient corresponding to the source frequency fs or by adding a correction amount corresponding to the source frequency fs. The degree of reflection may be determined from the corrected reflected wave signal and the corrected traveling wave signal. The correction coefficient or correction amount corresponding to the source frequency fs may be connected to the control unit 50c or stored in a table in the memory device of the control unit 50c. The table stores the correction coefficient or correction amount for each of the multiple source frequencies associated with each signal to be corrected. The control unit 50c may specify a correction coefficient or correction amount by referring to a table and obtain a correction signal such as a correction voltage signal, a correction current signal, a correction reflected wave signal, or a correction traveling wave signal.

[0043] The RF power supply 51 can determine a source frequency fs that reduces the degree of reflection of the source RF signal HF through feedback processing. In the feedback processing, the RF power supply 51 divides each repetition period RC included in the series of repetition periods RC into a plurality of phase periods PH. The repetition period RC is the repetition period of the source RF signal HF or the electrical bias EB. In the example of (a) in FIG. 6, the series of repetition periods RC is a series of waveform periods Cb. In the example of (b) in FIG. 6, the series of repetition periods RC may be a series of pulse periods Cp. Alternatively, in the example of (b) in FIG. 6, for the first partial period within the pulse period PP, the series of repetition periods RC may be a series of pulse periods Cp, and for the second partial period after the first partial period within the pulse period PP, the series of repetition periods RC may be a series of waveform periods Cb. Each waveform period Cb in the series of waveform periods Cb is divided into N phase periods PH as shown in FIG. 5. Also, each of the plurality of waveform periods Cb included in each pulse period Cp in the series of pulse periods Cp is divided into N phase periods PH.

[0044] The RF power supply 51 determines the source frequency fs for each phase period PH included in the series of repetition periods RC so as to reduce the degree of reflection according to the degree of reflection in the same past phase period PH in the series of repetition periods RC. For example, the RF power supply 51 determines the source frequency fs for each phase period PH included in the series of repetition periods RC so as to reduce the degree of reflection from the tendency of the degree of reflection obtained by using different source frequencies fs in the same past phase period PH in the series of repetition periods RC.

[0045] In addition, the RF power supply 51 changes the source frequency fs in the feedback process so that the source RF signal HF does not have a source frequency that generates an unwanted signal (or spurious signal) that is a harmonic signal and / or intermodulation distortion with respect to the source RF signal HF and has a signal level large enough not to satisfy the allowable conditions. Note that the intermodulation distortion can occur due to the interaction between the source RF signal HF and the harmonic signal with respect to the source RF signal, the interaction between two harmonic signals of the source RF signal, and the interaction between the source RF signal HF or the harmonic signal with respect to the source RF signal and the electrical bias EB or the harmonic signal of the electrical bias EB.

[0046] In one embodiment, an analyzer 58 may be used to detect the generation of an unwanted signal having a signal level large enough not to satisfy the allowable conditions. The analyzer 58 is configured to acquire the frequency spectrum of the signal flowing through the electrical path connecting the RF power supply 51 and the high-frequency electrode to each other. The analyzer 58 may be a spectrum analyzer or an FFT analyzer. Alternatively, the analyzer 58 may include a plurality of band-pass filters and a plurality of sensors. The plurality of band-pass filters have different pass bands. Each of the plurality of sensors is configured to acquire the signal level (power level or amplitude) of the signal that has passed through the corresponding band-pass filter among the plurality of band-pass filters. In this case, the frequency spectrum is generated based on the signal levels acquired by the plurality of sensors. The analyzer 58 may acquire the frequency spectrum from the voltage signal or current signal acquired by the sensor 55, or the traveling wave signal or reflected wave signal acquired by the sensor 56. Alternatively, the analyzer 58 may acquire the frequency spectrum from a correction signal such as the above-described correction voltage signal, correction current signal, correction reflected wave signal, or correction traveling wave signal.

[0047] The RF power supply 51 may change the source frequency fs so that the source RF signal HF does not have a source frequency that generates such an unwanted signal if an unwanted signal with a signal level too large to satisfy the tolerance condition is detected in the frequency spectrum acquired by the analyzer 58. The tolerance condition does not have to be satisfied if an unwanted signal with a signal level above or greater than the threshold is detected in the frequency spectrum, but it may be satisfied in other cases. In other words, the tolerance condition may be satisfied if no unwanted signal with a signal level above or greater than the threshold is detected in the frequency spectrum. Alternatively, the tolerance condition does not have to be satisfied if an unwanted signal with a signal level where the ratio of the source RF signal HF to the magnitude of the signal level at the source frequency fs (i.e., the fundamental frequency) is above or greater than the threshold is detected, but it may be satisfied in other cases. In other words, the tolerance condition may be satisfied if no unwanted signal with a signal level where the ratio of the source RF signal HF to the magnitude of the signal level at the source frequency fs (i.e., the fundamental frequency) is above or greater than the threshold is detected.

[0048] In one embodiment, the RF power supply 51 may perform the above-described feedback processing by setting a source frequency that generates an unwanted signal having a signal level too large to satisfy the acceptable conditions to be disabled. Alternatively, the RF power supply 51 may perform the above-described feedback processing by setting a frequency band including the source frequency that generates an unwanted signal having a signal level too large to satisfy the acceptable conditions to be disabled. The size of the frequency band to be disabled may be a predetermined width band including the source frequency to be disabled. The source frequency or frequency band to be disabled may be determined by the RF power supply 51, or it may be determined by the control unit 50c and specified to the RF power supply 51.

[0049] In one embodiment, the control unit 50c may adjust the capacitance of the variable capacitor 532 such that a source frequency that generates an unwanted signal with a signal level too large to satisfy the tolerance condition is not included between the upper and lower limits of the variable range of the source frequency fs. The variable range of the source frequency fs used to reduce the degree of reflection shifts to the high-frequency side or the low-frequency side as the capacitance of the variable capacitor 532 changes. As a result, the RF power supply 51 can change the source frequency fs to reduce the degree of reflection in a variable range that does not include a source frequency that generates an unwanted signal with a signal level too large to satisfy the tolerance condition. The control unit 50c may also adjust the capacitance of the variable capacitor 532 such that the proportion of time spent supplying a source RF signal HF having a source frequency that generates an unwanted signal with a signal level too large to satisfy the tolerance condition within a predetermined periodic period (e.g., the waveform period Cb described above) is less than or equal to a threshold (e.g., 50%).

[0050] According to the plasma processing apparatus 1 described above, unwanted signals with signal levels too high to meet the acceptable conditions are suppressed, thus increasing process stability. For example, variations in process results due to differences in the plasma processing apparatus 1 or in-plane variations in plasma processing on the substrate in the plasma processing apparatus 1 are suppressed, resulting in process stability. Furthermore, the plasma processing apparatus 1 makes it possible to reduce the degree of reflection of the source RF signal HF.

[0051] A frequency control method according to one exemplary embodiment will be described below with reference to Figure 7. Figure 7 is a flowchart showing a frequency control method according to one exemplary embodiment. The frequency control method shown in Figure 7 (hereinafter referred to as "Method MT") can be performed in the plasma processing apparatus 1 with the substrate W placed on the substrate support part 11. In each step of Method MT, each part of the plasma processing apparatus 1 can be controlled by the control unit 2 or the control unit 50c.

[0052] Method MT includes steps STa and STb. In step STa, a source RF signal HF is supplied from an RF power supply 51 to a high-frequency electrode to generate plasma from a gas in the chamber 10 of the plasma processing apparatus 1.

[0053] In step STb, it is determined whether unwanted signals are generated that include harmonic signals and / or intermodulation distortion in relation to the source RF signal HF and have a signal level that is too large to meet the acceptable conditions. For details on the detection of such unwanted signals, please refer to the above description of the plasma processing apparatus 1.

[0054] Figure 8 is a flowchart showing an example of a step STa in a frequency control method according to one exemplary embodiment. Step STa may include steps STa1 and STa2. In step STa1, the degree of reflection of the source RF signal HF supplied in step STa is determined. For details on the degree of reflection, please refer to the above description of the plasma processing apparatus 1.

[0055] In step STa2, the source frequency fs for each phase period PH is adjusted according to the degree of reflection. For details on the source frequency fs for each phase period PH, please refer to the explanation of the feedback process described above. If it is determined in step STb that an unwanted signal with a signal level too large to meet the tolerance conditions is generated, in step STa2, the source frequency fs is changed so that the source RF signal HF does not have a source frequency that generates an unwanted signal with a signal level too large to meet the tolerance conditions. In one embodiment, in step STa2, the source frequency fs is changed within a variable range of frequencies other than the source frequency or frequency band set to be prohibited as described above.

[0056] In one embodiment, in step STa2, the capacitance of the variable capacitor 532 may be adjusted so that a source frequency that generates an unwanted signal with a signal level too large to satisfy the allowable conditions is not included between the upper and lower limits of the variable range of the source frequency fs. Furthermore, in step STa2, the source frequency fs may be changed within the variable range of a frequency other than the source frequency or frequency band set to be prohibited as described above.As described above, the capacitance of the variable capacitor 532 may be adjusted so that the proportion of time spent supplying a source RF signal HF with a source frequency that generates an unwanted signal with a signal level too large to satisfy the allowable conditions within the waveform period Cb is 50% or less.

[0057] Returning to Figure 7, method MT may further include process STJ. In process STJ, it is determined whether or not a stop condition is met. The stop condition is met when the termination condition of a process or step performed in the plasma processing apparatus 1 is met. If it is determined in process STJ that the stop condition is not met, the processing from process STa is repeated. If it is determined in process STJ that the stop condition is met, method MT terminates.

[0058] The following describes examples of circuits (control circuits) that may constitute control unit 2 and / or control unit 50c.

[0059] Figure 9 illustrates a block diagram of a computer (a type of circuit) capable of implementing the various control modes described herein. Furthermore, the control modes of this disclosure can be implemented as a system, method, and / or computer program product. The computer program product may include a computer-readable storage medium on which computer-readable program instructions causing one or more processing units to execute the modes of this embodiment are recorded.

[0060] A computer-readable storage medium may be a tangible device capable of storing instructions used by an instruction execution device (processor). A computer-readable storage medium may, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination thereof. More specific examples of computer-readable storage media include, but are not exhaustive, flexible disks, hard disks, solid-state drives (SSDs), random-access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or Flash), static random-access memory (SRAM), compact disks (CDs or CD-ROMs), digital multipurpose disks (DVDs), memory cards or memory sticks (and suitable combinations thereof). In this disclosure, a computer-readable storage medium should not be interpreted as a transient signal itself, such as, for example, radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., optical pulses passing through optical fiber cables), or electrical signals transmitted via wires.

[0061] The computer-readable program instructions described in this disclosure can be downloaded from a computer-readable storage medium to a suitable computing device or processing device, or they can be downloaded to an external computer or external storage device via a global network (i.e., the Internet), a local area network, a wide area network, and / or a wireless network. Networks include transmission copper wires, optical fiber, wireless communications, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface of each computing device or processing device can receive computer-readable program instructions from the network, transfer those computer-readable program instructions, and store them in a computer-readable storage medium within the computing device or processing device.

[0062] Computer-readable program instructions for performing the operations of the Disclosure may include machine language instructions and / or microcode. These instructions can be compiled or interpreted from source code written in any combination of one or more programming languages, including assembly language, Basic, Fortran, Java®, Python, R, C, C++, C#, etc. Computer-readable program instructions can be fully executed on a user's personal computer, notebook computer, tablet, or smartphone, or may be fully executed on a remote computer or computer server, or on any combination of these computing devices. The remote computer or computer server may be connected to one or more of the user's devices via a computer network, including a local area network, a wide area network, or a global network (i.e., the Internet). Alternatively, electronic circuits, including, for example, programmable logic circuits, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), may be configured or customized to execute computer-readable program instructions using information from the computer-readable program instructions and implement embodiments of the Disclosure.

[0063] This specification will describe aspects of the present disclosure with reference to flowcharts and block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present disclosure. Those skilled in the art will understand that each block in the flowcharts and block diagrams, as well as combinations of blocks in the flowcharts and block diagrams, can be implemented by computer-readable program instructions.

[0064] Computer-readable program instructions capable of implementing the systems and methods described in this disclosure may be supplied to one or more processors (and / or one or more cores within a processor) of a general-purpose computer, a dedicated computer, or other programmable device. This makes it possible to generate a machine that constructs a system for implementing the functions specifically shown in the flowcharts and block diagrams of this disclosure, through instructions executed via the processors of the computer or other programmable device. These computer-readable program instructions may also be stored in a computer-readable storage medium that can instruct the computer, programmable device, and / or other device to function in a particular manner. The computer-readable storage medium storing the instructions is a product containing instructions that implement the embodiments of the functions specifically shown in the flowcharts and block diagrams of this disclosure.

[0065] Furthermore, computer-readable program instructions can be loaded into a computer, another programmable device, or other device, and a series of operations can be executed on that computer, other programmable device, or other device to realize a computer implementation process. Therefore, the functions specifically shown in the flowcharts and block diagrams of this disclosure can be realized by instructions executed on a computer, another programmable device, or other device.

[0066] Figure 9 is a functional block diagram showing a network system 800 in which one or more computers and servers are connected to a network. In one embodiment, the hardware and software environments illustrated in Figure 9 may serve as an exemplary platform for implementing the software and / or methods relating to this disclosure.

[0067] Referring to Figure 9, the network system 800 may include, but is not limited to, a computer 805, a network 810, a remote computer 815, a web server 820, a cloud storage server 825, and a computer server 830. In some embodiments, one or more examples of the functional blocks illustrated in Figure 9 may be used.

[0068] Further details of computer 805 are shown in Figure 9. The functional blocks illustrated within computer 805 are merely illustrative examples for constructing exemplary functions and do not encompass all of its functions. Details of the remote computer 815, web server 820, cloud storage server 825, and computer server 830 are not shown, but these computers and devices may also include functions similar to those shown for computer 805.

[0069] Computer 805 may be a personal computer (PC), desktop computer, laptop computer, tablet computer, netbook computer, personal data device (PDA), smartphone, or other programmable electronic device capable of communicating with other devices on the network 810.

[0070] The computer 805 may include a processing unit 835, a bus 837, a memory 840, a non-volatile storage device 845, a network interface 850, a peripheral device interface 855, and a display device interface 865. In some embodiments, these functions may be implemented as individual electronic subsystems (integrated circuit chips or combinations of chips and associated devices), while in other embodiments, some of the combinations of functions may be implemented on a single chip (also known as a system-on-a-chip or SoC).

[0071] The processing unit 835 may be one or more single-chip or multi-chip microprocessors designed and / or manufactured by Intel Corporation, Advanced Micro Devices, Inc. (AMD), Arm Holdings, Apple Computer, etc. Examples of microprocessors include Intel Corporation's Celeron, Pentium®, Core i3, Core i5, Core i7; AMD's Opteron, Phenom, Athlon, Turion, Ryzen; and Arm's Cortex-A, Cortex-R, Cortex-M, etc.

[0072] Bus 837 may be a proprietary or industry-standard high-speed parallel or serial peripheral interconnect bus such as ISA, PCI, PCI Express (PCI-e), or AGP.

[0073] The memory 840 and the non-volatile storage device 845 may be computer-readable storage media. The memory 840 may include any suitable volatile storage device such as dynamic random access memory (DRAM) and static random access memory (SRAM). The non-volatile storage device 845 may include one or more of the following: flexible disk, hard disk, solid-state drive (SSD), read-only memory (ROM), erasable programmable read-only memory (EPROM or Flash), compact disc (CD or CD-ROM), digital multipurpose disc (DVD), memory card, or memory stick.

[0074] The program 848 may be a collection of machine-readable instructions and / or machine-readable data stored in at least one memory, such as a non-volatile storage device 845, and used to create, manage, and control specific software functions as described in detail and illustrated in the drawings of this disclosure. In some embodiments, memory 840 may be much faster than the non-volatile storage device 845. In that case, the program 848 may be transferred from the non-volatile storage device 845 to memory 840 and then executed by the processing unit 835. The program 848 includes computer program code. In one implementation, at least one memory storing the computer program code comprises at least one processing unit (such as a processing circuit described later) for carrying out the control process and claimed advanced embodiments of this disclosure.

[0075] Computer 805 may communicate and interact with other computers via network 810 using network interface 850. Network 810 may be, for example, a local area network (LAN), a wide area network (WAN) such as the Internet, or a combination thereof, and may include wired, wireless, or fiber optic connections. In general, network 810 can be any combination of connections and protocols that support communication between two or more computers and associated devices.

[0076] The peripheral interface 855 may enable data input and output via other devices that can be locally connected to the computer 805. For example, the peripheral interface 855 may enable connection to an external device 860. The external device 860 may include devices such as a keyboard, mouse, keypad, touchscreen, and / or other suitable input devices. The external device 860 may also include portable computer-readable storage media such as a thumb drive, portable optical or magnetic disk, and memory card. Software and data used to implement embodiments of the present disclosure (e.g., program 848) may be stored on such portable computer-readable storage media. In this case, the software may be loaded into the non-volatile storage device 845, or directly into memory 840 via the peripheral interface 855. The peripheral interface 855 may use industry-standard connections such as RS-232 or Universal Serial Bus (USB) to connect to the external device 860.

[0077] The computer 805 may be connected to the display device 870 via the display device interface 865. In one embodiment, the display device 870 may be used to present a command line or a graphical user interface to the user of the computer 805. The display device interface 865 may be connected to the display device 870 using one or more proprietary or industry standard connections such as VGA, DVI, DisplayPort, HDMI®, etc.

[0078] As described above, the network interface 850 enables communication with other computing systems or storage systems or computing devices or storage devices outside of the computer 805. The software programs and data described herein may be downloaded to the non-volatile storage device 845 via the network interface 850 and network 810 from, for example, a remote computer 815, a web server 820, a cloud storage server 825, or a computer server 830. Furthermore, the systems and methods described herein may be implemented by one or more computers connected to the computer 805 via the network interface 850 and network 810. For example, in one embodiment, the systems and methods described herein may be implemented by a combination of a remote computer 815, a computer server 830, or computers interconnected on network 810.

[0079] The data, datasets, and / or databases used in the embodiments of the systems and methods described herein may be stored in or downloaded from a remote computer 815, a web server 820, a cloud storage server 825, or a computer server 830.

[0080] The circuits used in this application can be defined as one or more of the following: electronic components (such as semiconductor devices), a plurality of electronic components directly connected to each other or interconnected via electronic communication, a computer, a network of computer devices, a remote computer, a web server, a cloud storage server, or a computer server. For example, each of the one or more of the computer, remote computer, web server, cloud storage server, and computer server may be included as a component of the circuit, or may include the circuit. In some embodiments, one or more examples of these components may be used, and each of the one or more examples of these components may also be included in the circuit, or may include the circuit. In some embodiments, a circuit represented by a network system may include a serverless computing system that corresponds to virtualized hardware resources. A circuit represented by a computer may be a personal computer (PC), a desktop computer, a laptop computer, a tablet computer, a netbook computer, a personal data device (PDA), a smartphone, or other programmable electronic device that can communicate with other devices on a network. The circuit may be a general-purpose computer, a dedicated computer, or other programmable device described herein that includes one or more processing units. Each processing unit may be one or more single-chip microprocessors or multi-chip microprocessors. One or more processing units are considered processing circuits or circuits because they incorporate transistors and other circuits. The circuits can implement the systems and methods described in this disclosure based on computer-readable program instructions. These program instructions are supplied to one or more processing units (and / or one or more cores within processing units) of one or more general-purpose computers, dedicated computers, or other programmable devices described herein. This makes it possible to generate a machine that constructs a system for implementing the functions specifically shown in the flowcharts and block diagrams of this disclosure, through instructions contained within the circuits or executed via one or more processing units of a programmable device containing the circuits.Alternatively, a circuit may be a pre-programmed structure, such as a programmable logic device or an application-specific integrated circuit. A circuit is considered a circuit whether it is used alone or in combination with other programmable circuits or other pre-programmed circuits.

[0081] In light of the above teachings, it is clear that numerous modifications and variations of the present invention are possible. Therefore, it should be understood that, within the scope of the appended claims, the present invention can be implemented in forms other than those specifically described herein.

[0082] Although various exemplary embodiments have been described above, the invention is not limited to the exemplary embodiments described above, and various additions, omissions, substitutions, and modifications may be made. Furthermore, it is possible to combine elements from different embodiments to form other embodiments.

[0083] Herein, various exemplary embodiments included in this disclosure are described in [E1] to [E15] below.

[0084] [E1] A plasma processing apparatus comprising: a chamber; a substrate support within the chamber; and an RF power supply configured to supply a source RF signal to a high-frequency electrode for generating plasma from a gas within the chamber, the RF power supply configured to change the source frequency of the source RF signal according to the degree of reflection so as to reduce the degree of reflection of the source RF signal from the load, wherein the RF power supply is configured to change the source frequency such that the source RF signal does not have a source frequency that generates an unwanted signal including harmonic signals and / or intermodulation distortion to the source RF signal and having a signal level that is too large to meet acceptable conditions.

[0085] [E2] The plasma processing apparatus according to E1, further comprising an analyzer configured to acquire the frequency spectrum of a signal flowing through an electrical path connecting the RF power supply and the high-frequency electrode, wherein the RF power supply is configured to change the source frequency such that, when an unwanted signal having a signal level too large to satisfy the tolerance is detected in the frequency spectrum acquired by the analyzer, the source RF signal does not have a source frequency that generates the unwanted signal having a signal level too large to satisfy the tolerance.

[0086] [E3] The plasma apparatus according to E1 or E2, wherein the RF power supply is configured to disable the use of the source frequency that generates the unwanted signal having a signal level so large as to not satisfy the tolerance condition, or to disable the use of a frequency band that includes the source frequency that generates the unwanted signal having a signal level so large as to not satisfy the tolerance condition.

[0087] [E4] The plasma apparatus according to E1 or E2, further comprising: a matching unit including a variable capacitor connected between the RF power supply and the high-frequency electrode; and a control unit, wherein the control unit is configured to adjust the capacitance of the variable capacitor such that the source frequency that generates the unwanted signal having a signal level so large as to not satisfy the tolerance condition does not fall between the upper and lower limits of the variable range of the source frequency.

[0088] [E5] The plasma processing apparatus according to any one of E1 to E4, further comprising a bias power supply electrically coupled to the substrate support and configured to periodically supply an electrical bias to draw ions from the plasma to a substrate on the substrate support, wherein the RF power supply is configured to adjust the source frequency for each phase period within the repetition period of the source RF signal or the electrical bias, in accordance with the degree of reflection of the source RF signal in a past same phase period.

[0089] [E6] The plasma processing apparatus according to E5, wherein the repetition period is the waveform period of the electrical bias.

[0090] [E7] The plasma processing apparatus according to E5, wherein the repetition period is the pulse generation period of the source RF signal.

[0091] [E8] An RF power supply configured to supply a source RF signal to a high-frequency electrode for generating plasma from a gas in a chamber of a plasma processing apparatus, the RF power supply configured to change the source frequency of the source RF signal in accordance with the degree of reflection of the source RF signal from a load, to reduce the degree of reflection of the source RF signal from the load; and a bias power supply electrically coupled to a substrate support in a chamber of a plasma processing apparatus, configured to periodically supply an electrical bias for drawing ions from the plasma to a substrate on the substrate support, wherein the RF power supply is configured to change the source frequency such that the source RF signal does not have a source frequency that generates an unwanted signal including harmonic signals and / or intermodulation distortion to the source RF signal having a signal level that is too large to meet acceptable conditions.

[0092] [E9] The power supply system according to E8, further comprising an analyzer configured to acquire the frequency spectrum of a signal flowing through an electrical path connecting the RF power supply and the high-frequency electrode to each other, wherein the RF power supply is configured to change the source frequency such that, when an unwanted signal having a signal level too large to satisfy the tolerance is detected in the frequency spectrum acquired by the analyzer, the source RF signal does not have a source frequency that generates the unwanted signal having a signal level too large to satisfy the tolerance.

[0093] [E10] The power supply system according to E8 or E9, wherein the RF power supply is configured to disable the use of the source frequency that generates the unwanted signal having a signal level that is too high to satisfy the tolerance, or to disable the use of a frequency band that includes the source frequency that generates the unwanted signal having a signal level that is too high to satisfy the tolerance.

[0094] [E11] The power supply system according to E8 or E9, further comprising: a matching circuit including a variable capacitor connected between the RF power supply and the high-frequency electrode; and a control unit, wherein the control unit is configured to adjust the capacitance of the variable capacitor such that the source frequency that generates the unwanted signal having a signal level so large as to not satisfy the tolerance condition does not fall between the upper and lower limits of the variable range of the source frequency.

[0095] [E12] The power supply system according to any one of E8 to E11, wherein the RF power supply is configured to adjust the source frequency for each phase period within the repetition period of the source RF signal or the electrical bias, in accordance with the degree of reflection of the source RF signal in a past same phase period.

[0096] [E13] The power supply system according to E12, wherein the repetition period is the waveform period of the electrical bias.

[0097] [E14] The power supply system according to E12, wherein the repetition period is the pulse generation period of the source RF signal.

[0098] [E15] A frequency control method comprising: (a) a step of supplying a source RF signal from an RF power supply to a high-frequency electrode in order to generate plasma from a gas in a chamber of a plasma processing apparatus, the step of changing the source frequency of the source RF signal in accordance with the degree of reflection so as to reduce the degree of reflection of the source RF signal from the load of the RF power supply; and (b) a step of determining in (a) whether an unwanted signal is generated which includes harmonic signals and / or intermodulation distortion to the source RF signal and has a signal level that is too large to satisfy an acceptable condition, wherein in (b) it is determined that an unwanted signal has a signal level that is too large to satisfy an acceptable condition, the source frequency is changed in (a) such that the source RF signal does not have a source frequency that generates the unwanted signal having a signal level that is too large to satisfy an acceptable condition.

[0099] From the above description, it will be understood that the various embodiments of this disclosure are described herein for illustrative purposes and can be modified in various ways without departing from the scope and spirit of this disclosure. Accordingly, the various embodiments disclosed herein are not intended to limit the scope and spirit, and the true scope and spirit are shown by the appended claims.

[0100] 1...Plasma processing apparatus, 10...Chamber, 11...Substrate support section, 50...Power supply system, 51...RF power supply, 52...Bias power supply, 53...Matching unit, 532...Variable capacitor, 58...Analyzer, 50c...Control unit.

Claims

1. A plasma processing apparatus comprising: a chamber; a substrate support within the chamber; and an RF power supply configured to supply a source RF signal to a high-frequency electrode for generating plasma from a gas within the chamber, the RF power supply configured to change the source frequency of the source RF signal according to the degree of reflection so as to reduce the degree of reflection of the source RF signal from the load, wherein the RF power supply is configured to change the source frequency such that the source RF signal does not have a source frequency that generates an unwanted signal including harmonic signals and / or intermodulation distortion to the source RF signal having a signal level that is too large to meet acceptable conditions.

2. The plasma processing apparatus according to claim 1, further comprising an analyzer configured to acquire the frequency spectrum of a signal flowing through an electrical path connecting the RF power supply and the high-frequency electrode, wherein the RF power supply is configured to change its source frequency so as not to have a source frequency that generates the unwanted signal having a signal level too large to satisfy the tolerance when an unwanted signal having a signal level too large to satisfy the tolerance is detected in the frequency spectrum acquired by the analyzer.

3. The plasma processing apparatus according to claim 2, wherein the RF power supply is configured to disable the use of the source frequency that generates the unwanted signal having a signal level so large as to not satisfy the tolerance condition, or to disable the use of a frequency band that includes the source frequency that generates the unwanted signal having a signal level so large as to not satisfy the tolerance condition.

4. The plasma processing apparatus according to claim 2, further comprising: a matching unit including a variable capacitor connected between the RF power supply and the high-frequency electrode; and a control unit, wherein the control unit is configured to adjust the capacitance of the variable capacitor such that the source frequency that generates the unwanted signal having a signal level so large as to not satisfy the tolerance condition does not fall between the upper and lower limits of the variable range of the source frequency.

5. The plasma apparatus according to any one of claims 1 to 4, further comprising a bias power supply electrically coupled to the substrate support and configured to periodically supply an electrical bias to draw ions from the plasma to a substrate on the substrate support, wherein the RF power supply is configured to adjust the source frequency for each phase period within the repetition period of the source RF signal or the electrical bias, in accordance with the degree of reflection of the source RF signal in a past same phase period.

6. The plasma processing apparatus according to claim 5, wherein the repetition period is the waveform period of the electrical bias.

7. The plasma processing apparatus according to claim 5, wherein the repetition period is the pulse generation period of the source RF signal.

8. An RF power supply configured to supply a source RF signal to a high-frequency electrode for generating plasma from a gas in a chamber of a plasma processing apparatus, the RF power supply configured to change the source frequency of the source RF signal in accordance with the degree of reflection of the source RF signal from the load, to reduce the degree of reflection of the source RF signal from the load; and a bias power supply electrically coupled to a substrate support in a chamber of a plasma processing apparatus, configured to periodically supply an electrical bias for drawing ions from the plasma to a substrate on the substrate support, wherein the RF power supply is configured to change the source frequency such that the source RF signal does not have a source frequency that generates an unwanted signal including harmonic signals and / or intermodulation distortion to the source RF signal having a signal level that is too large to meet acceptable conditions.

9. The power supply system according to claim 8, further comprising an analyzer configured to acquire the frequency spectrum of a signal flowing through an electrical path connecting the RF power supply and the high-frequency electrode to each other, wherein the RF power supply is configured to change its source frequency such that, when an unwanted signal having a signal level too large to satisfy the tolerance is detected in the frequency spectrum acquired by the analyzer, the source RF signal does not have a source frequency that generates the unwanted signal having a signal level too large to satisfy the tolerance.

10. The power supply system according to claim 9, wherein the RF power supply is configured to disable the use of the source frequency that generates the unwanted signal having a signal level that is too high to satisfy the tolerance, or to disable the use of a frequency band that includes the source frequency that generates the unwanted signal having a signal level that is too high to satisfy the tolerance.

11. The power supply system according to claim 9, further comprising: a matching circuit including a variable capacitor connected between the RF power supply and the high-frequency electrode; and a control unit, wherein the control unit is configured to adjust the capacitance of the variable capacitor such that the source frequency that generates the unwanted signal having a signal level so large as to not satisfy the tolerance condition does not fall between the upper and lower limits of the variable range of the source frequency.

12. The power supply system according to any one of claims 8 to 11, wherein the RF power supply is configured to adjust the source frequency for each phase period within the repetition period of the source RF signal or the electrical bias, in accordance with the degree of reflection of the source RF signal in a past same phase period.

13. The power supply system according to claim 12, wherein the repetition period is the waveform period of the electrical bias.

14. The power supply system according to claim 12, wherein the repetition period is the pulse generation period of the source RF signal.

15. A frequency control method comprising: (a) a step of supplying a source RF signal from an RF power supply to a high-frequency electrode in order to generate plasma from a gas in a chamber of a plasma processing apparatus, the step of changing the source frequency of the source RF signal in accordance with the degree of reflection so as to reduce the degree of reflection of the source RF signal from the load of the RF power supply; and (b) a step of determining in (a) whether an unwanted signal including harmonic signals and / or intermodulation distortion to the source RF signal is generated and has a signal level that is too large to satisfy an acceptable condition, wherein in (b) it is determined that an unwanted signal having a signal level that is too large to satisfy an acceptable condition is generated, and in (a) the source frequency is changed so that the source RF signal does not have a source frequency that generates the unwanted signal having a signal level that is too large to satisfy an acceptable condition.

Images