Plasma processing device

Abstract

Provided is a technique for measuring electrical characteristics of a chamber. Provided is a plasma processing device. The plasma processing device includes: a chamber; an RF power supply; a measuring instrument that periodically or continuously determines an RF reflection characteristic at a node between the chamber and the RF power supply; a storage unit that stores a static characteristic; and a control unit that executes a plasma ignition determination sequence. The plasma ignition determination sequence includes: comparing the periodically or continuously determined RF reflection characteristic with the static characteristic stored in the storage unit; determining that the plasma has not been ignited in the chamber when the difference between the RF reflection characteristic and the static characteristic is equal to or less than a threshold; and determining that the plasma has been ignited in the chamber when the difference is larger than the threshold. The static characteristic is an RF reflection characteristic at the node when a low-output RF signal is supplied from the RF power supply to the chamber. The low-output RF signal has power to the extent that the plasma is not ignited in the chamber.

Description

Plasma processing equipment

[0001] SUMMARY OF THE INVENTION An exemplary embodiment of the present disclosure relates to a plasma processing apparatus.

[0002] Patent Document 1 discloses a method for calibrating a high frequency measuring device that measures high frequency parameters in a chamber.

[0003] JP 2011-202973 A

[0004] The present disclosure provides techniques for measuring electrical characteristics of a chamber.

[0005] In one exemplary embodiment of the present disclosure, there is provided a plasma processing apparatus including: a chamber; an RF power source coupled to the chamber; a measurement instrument configured to periodically or continuously determine an RF reflection characteristic at a node between the chamber and the RF power source; a memory unit configured to store a static characteristic, the static characteristic being an RF reflection characteristic at the node when a low-power RF signal is supplied to the chamber from the RF power source, the low-power RF signal having a power level that does not ignite plasma in the chamber; and a controller configured to execute a plasma ignition determination sequence, the plasma ignition determination sequence including: comparing the periodically or continuously determined RF reflection characteristic with the static characteristic stored in the memory unit; determining that plasma has not been ignited in the chamber if a difference between the compared RF reflection characteristic and the static characteristic is equal to or less than a threshold; and determining that plasma has been ignited in the chamber if the difference between the compared RF reflection characteristic and the static characteristic is greater than the threshold.

[0006] According to one exemplary embodiment of the present disclosure, a technique for measuring an electrical characteristic of a chamber can be provided.

[0007] 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 example of the configuration of an inductively coupled plasma processing apparatus; FIG. 3 is a diagram for explaining an example of an RF system; FIG. 4 is a diagram for explaining another example of an RF system; FIG. 5 is a flowchart for explaining an example of a static characteristic determination sequence; FIG. 6 is a diagram for explaining an example of a plasma ignition determination sequence;

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

[0009] In one exemplary embodiment, a plasma processing apparatus is provided that includes: a chamber; an RF power source coupled to the chamber; a measurement instrument configured to periodically or continuously determine an RF reflection characteristic at a node between the chamber and the RF power source; a memory unit configured to store a static characteristic, the static characteristic being an RF reflection characteristic at the node when a low-power RF signal is supplied to the chamber from the RF power source, the low-power RF signal having a power level that does not ignite plasma in the chamber; and a controller configured to execute a plasma ignition determination sequence, the plasma ignition determination sequence including: comparing the periodically or continuously determined RF reflection characteristic with the static characteristic stored in the memory unit; determining that plasma has not been ignited in the chamber if a difference between the compared RF reflection characteristic and the static characteristic is less than or equal to a threshold; and determining that plasma has been ignited in the chamber if the difference between the compared RF reflection characteristic and the static characteristic is greater than the threshold.

[0010] In one exemplary embodiment, the RF reflection characteristics are determined from the voltages and currents sensed at the nodes.

[0011] In one exemplary embodiment, the static characteristics include RF reflection characteristics for each frequency of the low-power RF signal.

[0012] In one exemplary embodiment, the RF reflection characteristics include one or more of the following at the node: (a) the power ratio of the forward wave to the reflected wave; (b) the resistive component of the impedance (Ω); (c) the reflection coefficient; (d) the return loss (dB); and (e) the S-parameters (dB).

[0013] In one exemplary embodiment, the system further comprises an impedance matching circuit connected between the chamber and the measurement instrument.

[0014] In one exemplary embodiment, the system further comprises an impedance matching circuit connected between the RF power source and the measurement instrument.

[0015] In one exemplary embodiment, the control unit is further configured to execute a static characteristic determination sequence, the static characteristic determination sequence including sequentially supplying a plurality of low-power RF signals from an RF power supply to the chamber, each of the plurality of low-power RF signals having a different frequency from each other, acquiring an RF reflection characteristic for each frequency in a measurement instrument, and storing the acquired RF reflection characteristic for each frequency as a static characteristic in a memory unit.

[0016] In one exemplary embodiment, the static characterization sequence is performed with no plasma generated in the chamber and the low-power RF signal has a power of less than 10 W.

[0017] In one exemplary embodiment, the chamber further includes another RF power supply configured to generate a source RF signal to generate a plasma in the chamber, and the static characterization sequence is performed while the plasma is being generated in the chamber by the source RF signal provided by the other RF power supply, and the low-power RF signal has a power of less than 1 W.

[0018] In one exemplary embodiment, the static characterization sequence is performed periodically based on the operating time of the RF power supply.

[0019] In one exemplary embodiment, the controller determines the frequency of the RF ignition signal used to ignite the plasma in the chamber based on static characteristics stored in the memory.

[0020] In one exemplary embodiment, the frequency of the RF ignition signal is selected from one or more frequencies that exhibit characteristic RF reflection characteristics in the static characteristic.

[0021] In one exemplary embodiment, the controller is configured to transition to a matching operation using an impedance matching circuit when the controller determines that a plasma has been ignited in the chamber.

[0022] In one exemplary embodiment, a plasma processing apparatus is provided, comprising: a chamber; an RF power source coupled to the chamber; a measurement device configured to periodically or continuously determine an RF reflection characteristic at a node between the chamber and the RF power source; a memory; and a controller configured to execute a static characterization sequence, the static characterization sequence including sequentially supplying a plurality of low-power RF signals from the RF power source to the chamber, each of the plurality of low-power RF signals having a different frequency and a power level sufficient to prevent plasma ignition in the chamber; acquiring the RF reflection characteristic for each frequency in the measurement device; and storing the acquired RF reflection characteristic for each frequency in the memory.

[0023] In one exemplary embodiment, the static characterization sequence is performed with no plasma generated in the chamber and the low-power RF signal has a power of less than 10 W.

[0024] In one exemplary embodiment, the chamber further includes another RF power supply configured to generate a source RF signal to generate a plasma in the chamber, and the static characterization sequence is performed while the plasma is being generated in the chamber by the source RF signal provided by the other RF power supply, and the low-power RF signal has a power of less than 1 W.

[0025] In one exemplary embodiment, the static characterization sequence is performed periodically based on the operating time of the RF power supply.

[0026] In one exemplary embodiment, a plasma processing apparatus is provided that includes: a chamber; an RF power source coupled to the chamber; a measurement instrument configured to periodically or continuously determine an RF reflection characteristic at a node between the chamber and the RF power source; a memory unit configured to store a static characteristic, the static characteristic being an RF reflection characteristic at the node when an RF signal is supplied to the chamber from the RF power source under conditions in which plasma is not ignited; and a controller configured to execute a plasma ignition determination sequence, wherein the plasma ignition determination sequence includes comparing the periodically or continuously determined RF reflection characteristic with the static characteristic stored in the memory unit; determining that plasma has not been ignited in the chamber if a difference between the compared RF reflection characteristic and the static characteristic is less than or equal to a threshold; and determining that plasma has been ignited in the chamber if the difference between the compared RF reflection characteristic and the static characteristic is greater than the threshold.

[0027] In one exemplary embodiment, the control unit is further configured to execute a static characteristic determination sequence, the static characteristic determination sequence including sequentially supplying a plurality of RF signals from the RF power source to the chamber under conditions where plasma is not ignited, each of the plurality of low-power RF signals having a different frequency from each other; acquiring RF reflection characteristics for each frequency in a measurement device; and storing the acquired RF reflection characteristics for each frequency in a memory unit as static characteristics.

[0028] 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.

[0029] <Configuration example of plasma processing system>

[0030] FIG. 1 is a diagram illustrating an exemplary 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 generated in the plasma processing space may be capacitively coupled plasma (CCP), inductively coupled plasma (ICP), electron-cyclotron-resonance plasma (ECR plasma), helicon wave plasma (HWP), surface wave plasma (SWP), or the like. Various types of plasma generators may be used, including alternating current (AC) plasma generators and direct current (DC) plasma generators. 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. Thus, AC signals include radio frequency (RF) signals and microwave signals. In one embodiment, the RF signal has a frequency in the range of 100 kHz to 150 MHz.

[0032] The control unit 2 processes computer-executable instructions that cause the plasma processing apparatus 1 to perform various processes described in this disclosure. The control unit 2 may be configured to control each element of the plasma processing apparatus 1 to perform 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 may include a processing unit 2a1, a storage unit 2a2, and a communication interface 2a3. The control unit 2 may be implemented by, for example, a computer 2a. The processing unit 2a1 may be configured to read a program from the storage unit 2a2 and execute the read program to perform various control operations. This program may be stored in the storage 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 processing unit 2a1 may be a CPU (Central Processing Unit). 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).

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

[0034] The inductively coupled plasma processing apparatus 1 includes a plasma processing chamber 10, a gas supply unit 20, a power supply 30, and an exhaust system 40. The plasma processing chamber 10 includes a dielectric window 101. The plasma processing apparatus 1 also includes a substrate support 11, a gas inlet, and an antenna 14. The substrate support 11 is disposed within the plasma processing chamber 10. The antenna 14 is disposed on or above the plasma processing chamber 10 (i.e., on or above the dielectric window 101). The plasma processing chamber 10 has a plasma processing space 10s defined by the dielectric window 101, a sidewall 102 of the plasma processing chamber 10, and the substrate support 11. The plasma processing chamber 10 is grounded.

[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 can function as a bias electrode. The electrostatic chuck 1111 is disposed on the base 1110. The electrostatic chuck 1111 includes a ceramic member 1111a and an electrostatic electrode 1111b disposed within the ceramic member 1111a. 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 also be provided by 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. Furthermore, at least one RF / DC electrode coupled to an RF power supply 31 and / or a DC power supply 32, which will be described later, may be disposed within the ceramic member 1111a. In this case, the at least one RF / DC electrode functions as a bias electrode. Note that the conductive member of the base 1110 and the at least one RF / DC electrode may function as multiple bias electrodes. Alternatively, the electrostatic electrode 1111b may function as a bias electrode. Therefore, the substrate support 11 includes at least one bias 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 gas inlet is configured to introduce at least one process gas from the gas supply unit 20 into the plasma processing space 10s. In one embodiment, the gas inlet includes a center gas injector (CGI) 13. The center gas injector 13 is disposed above the substrate support 11 and attached to a central opening formed in the dielectric window 101. The center gas injector 13 has at least one gas supply port 13a, at least one gas flow path 13b, and at least one gas inlet port 13c. The process gas supplied to the gas supply port 13a passes through the gas flow path 13b and is introduced into the plasma processing space 10s from the gas inlet port 13c. Note that the gas inlet may include one or more side gas injectors (SGIs) attached to one or more openings formed in the sidewall 102 in addition to or instead of the center gas injector 13.

[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 gas inlet through 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 30 includes an RF power supply 31 coupled to the plasma processing chamber 10 via at least one impedance matching circuit. The RF power supply 31 is configured to supply at least one RF signal (RF power) to at least one bias electrode and the antenna 14. This causes a plasma to be formed from at least one processing gas supplied to the plasma processing space 10s. Therefore, the RF power supply 31 can function as at least a part of the plasma generating unit 12. Furthermore, by supplying a bias RF signal to the at least one bias electrode, a bias potential is generated on the substrate W, thereby attracting ions in the formed plasma to the substrate W.

[0042] In one embodiment, the RF power supply 31 includes a first RF generating unit 31a and a second RF generating unit 31b. The first RF generating unit 31a is coupled to the antenna 14 via at least one impedance matching circuit and is configured to generate a source RF signal (source RF power) for plasma generation. 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 generating unit 31a may be configured to generate multiple source RF signals having different frequencies. The generated one or more source RF signals are supplied to the antenna 14.

[0043] The second RF generator 31b is coupled to at least one bias electrode via at least one impedance matching circuit and is configured to generate a bias RF signal (bias RF power). 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 bias electrode. In various embodiments, at least one of the source RF signal and the bias RF signal may be pulsed.

[0044] The power supply 30 may also include a DC power supply 32 coupled to the plasma processing chamber 10. The DC power supply 32 includes a bias DC generator 32a. In one embodiment, the bias DC generator 32a is connected to at least one bias electrode and configured to generate a bias DC signal. The generated bias DC signal is applied to the at least one bias electrode.

[0045] In various embodiments, the bias DC signal may be pulsed. In this case, a sequence of voltage pulses is applied to at least one bias electrode. The voltage pulses may have a rectangular, trapezoidal, triangular, or combination thereof. In one embodiment, a waveform generator for generating the sequence of voltage pulses from the DC signal is connected between the bias DC generator 32a and at least one bias electrode. Thus, the bias DC generator 32a and the waveform generator constitute a voltage pulse generator. The voltage pulses may have positive or negative polarity. Furthermore, the sequence of voltage pulses may include one or more positive voltage pulses and one or more negative voltage pulses within one cycle. Note that the bias DC generator 32a may be provided in addition to the RF power supply 31 or may be provided instead of the second RF generator 31b.

[0046] The antenna 14 includes one or more coils. In one embodiment, the antenna 14 may include an outer coil and an inner coil arranged coaxially. In this case, the RF power supply 31 may be connected to both the outer coil and the inner coil, or to either the outer coil or the inner coil. In the former case, the same RF generator may be connected to both the outer coil and the inner coil, or separate RF generators may be connected to the outer coil and the inner coil separately.

[0047] 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.

[0048] <Example of RF System> FIG. 3 is a diagram showing an example of a system configuration (hereinafter also referred to as an "RF system") from the RF power supply 31 to the chamber 10. As shown in FIG. 3, a first RF generation unit (RF1) 31a is connected to a plasma processing chamber 10 (hereinafter also referred to as "chamber 10") via a first transmission line TLa. The first transmission line TLa is a signal line through which a first RF signal (source RF signal) generated by the first RF generation unit 31a propagates. A first RF measurement unit 33a and a first matching circuit 34a are arranged on the first transmission line TLa from upstream (RF power supply 31) to downstream (chamber 10), in this order. That is, the first RF generation unit 31a of the RF power supply 31 is coupled to the chamber 10 via the first RF measurement unit 33a and the first matching circuit 34a on the first transmission line TLa.

[0049] The first RF measurement unit 33a is configured to periodically or continuously determine the RF reflection characteristic of the first RF signal propagating through the first transmission path TLa. The RF reflection characteristic is a parameter related to the return amount (power of the reflected wave) relative to the output (power of the traveling wave) of the RF signal in the transmission path. The RF reflection characteristic will be described in detail later.

[0050] The first RF measurement section 33a includes a first directional coupler (DR1) 330a and a first VI sensor (VI1) 332a.

[0051] The first directional coupler 330a and the first VI sensor 332a each detect signal information for determining RF reflection characteristics of the first RF signal. The signal information detected by the first directional coupler 330a includes, for example, information about the forward wave power (Pf) and reflected wave power (Pr) of the first RF signal at the input (node) of the first matching circuit 34a. The signal information detected by the first VI sensor 332a includes, for example, information about the effective voltage (V), effective current (I), and phase difference (θ) between the voltage and current of the first RF signal at the input (node) of the first matching circuit 34a.

[0052] The first matching circuit 34a is configured to match the impedance of the chamber 10 and the first RF generating unit 31. The first matching circuit 34a includes a variable reactance element (e.g., a variable capacitor, a variable inductor, etc.). By controlling the variable reactance element of the first matching circuit 34a, the impedance of the first RF generating unit 31a with respect to the chamber 10 is controlled.

[0053] As shown in FIG. 3 , the second RF generating unit (RF2) 31b is connected to the chamber 10 via a second transmission line TLb. The second transmission line TLb is a signal line through which a second RF signal (bias signal) generated by the second RF generating unit 31b propagates. A second RF measurement unit 33b and a second matching circuit 34b are arranged on the second transmission line TLb in this order from upstream to downstream. That is, the second RF generating unit 31b of the RF power supply 31 is coupled to the chamber 10 via the second RF measurement unit 33b and the second matching circuit 34b on the second transmission line TLb. Note that the configurations of the second RF measurement unit 33b and the second matching circuit 34b may be similar to those of the first RF measurement unit 33a and the first matching circuit 34a described above, respectively.

[0054] FIG. 4 is a diagram showing another example of an RF system. In the example shown in FIG. 4, the positional relationship between the RF measurement units (33a, 33b) and the matching circuits (34a, 34b) is the opposite of that in the example shown in FIG. 3. That is, in the example shown in FIG. 4, the first matching circuit 34a and the first RF measurement unit 33a are arranged in this order from upstream to downstream on the first transmission line TLa. Also, the second matching circuit 34b and the second RF measurement unit 33b are arranged in this order from upstream to downstream on the second transmission line TLb. That is, the signal information detected by the directional coupling groups (330a, 330b) and the VI sensors (332a, 332b) is information on the RF signals at the output ends (nodes) of the matching circuits (34a, 34b).

[0055] Each component of the RF system may be controlled by the control unit 2. The control unit 2 controls each component of the RF system to acquire, store, and / or analyze electrical characteristics of the chamber 10. For example, the control unit 2 may execute a "static characteristic determination sequence" and / or a "plasma ignition determination sequence" as described below.

[0056] <Example of Static Characteristic Determination Sequence> The static characteristic determination sequence is a sequence for determining static characteristics. Here, the static characteristics are RF reflection characteristics when an RF signal is supplied from the RF power supply 31 to the chamber 10 under conditions in which plasma is not ignited in the chamber 10. For example, the static characteristics are RF reflection characteristics when a signal having a power level that does not ignite plasma (hereinafter also referred to as a "low-power RF signal") is supplied from the RF power supply 31 to the chamber 10. The static characteristics may include RF reflection characteristics for multiple different frequencies. That is, the static characteristic determination sequence may be a process of acquiring RF reflection characteristics for multiple different frequencies and saving them as static characteristics. The static characteristic determination sequence may be executed at an appropriate timing, such as before shipment of the plasma processing apparatus 1, upon initial operation after shipment (after installation on a production line), upon restarting operation, or after a certain period of time has elapsed since operation. In one embodiment, the static characteristic determination sequence may be executed periodically based on the operating time of the RF power supply 31.

[0057] In one embodiment, the static characterization sequence may be performed by supplying a low-power RF signal from the first RF generator 31 a while no plasma is generated in the chamber 10. Note that the static characterization sequence may also be performed by supplying a low-power RF signal from the second RF generator 31 b, an example of which will be described later.

[0058] 5 is a flowchart showing an example of a static characteristics determination sequence. As shown in FIG. 5, the static characteristics determination sequence may include step ST10 of setting the frequency of an RF signal, step ST12 of supplying a low-power RF signal, step ST14 of acquiring an RF reflection characteristic, step ST16 of determining whether a stop condition is satisfied, and step ST18 of storing the static characteristics.

[0059] In step ST10, the frequency of the low-power RF signal supplied from the first RF generator 31a is set. The static characteristic determination sequence is repeated multiple times until a stop condition (step ST16) is satisfied. In one embodiment, in the first cycle, a frequency (hereinafter also referred to as the "minimum frequency") that is, for example, 10% lower than the design frequency (e.g., 27 MHz) of the first RF signal may be set. In the second and subsequent cycles, a frequency slightly higher than the frequency set in the previous cycle may be set. That is, the set frequency may be gradually increased with each cycle. Then, in the last cycle, a frequency (hereinafter also referred to as the "maximum frequency") that is, for example, 10% higher than the design frequency may be set. In one embodiment, the frequency may be set to gradually decrease from the maximum frequency to the minimum frequency as the cycle increases. In another embodiment, the frequency may be set to a different value for each cycle within the range from the minimum frequency to the maximum frequency. Note that the minimum and maximum frequencies are not limited to ±10% of the design frequency and may be set as appropriate.

[0060] In step ST12, a low-power RF signal is supplied from the first RF generating unit 31a. The low-power RF signal has a power level that does not generate plasma in the chamber 10. That is, even if the first RF generating unit 31a supplies a low-power RF signal, plasma is not generated in the chamber 10. In one example, the low-power RF signal may have a power of less than 10 W, less than 5 W, or less than 1 W.

[0061] In step ST14, the RF reflection characteristic is acquired. Specifically, the first RF measurement unit 33a (see FIGS. 3 and 4) acquires the RF reflection characteristic of the first RF signal (low-power RF signal) propagating through the first transmission line TLa. The RF reflection characteristic is a parameter related to the amount of return (power of reflected wave) relative to the output (power of forward wave) of the RF signal in the transmission line.

[0062] In one embodiment, the RF reflection characteristics may be determined based on signal information detected by the first directional coupling group 330a and / or the first VI sensor 332a. The signal information detected by the first directional coupling group 330a may include, for example, information on the forward wave power (Pf) and reflected wave power (Pr) of the first RF signal (low-power RF signal) at the input or output terminal (node) of the first matching circuit 34a. The signal information detected by the first VI sensor 332a may include, for example, information on the effective voltage (V), effective current (I), and phase difference (θ) between the voltage and current of the first RF signal (low-power RF signal) at the input or output terminal (node) of the first matching circuit 34a.

[0063] In one embodiment, the RF reflection characteristics may include any one or more of the following (a) to (e) at the input end or output end of the first matching circuit 34a: (a) the ratio Ra of the power of the forward wave (Pf) to the power of the reflected wave (Pr) (see Equation 1), (b) the resistance component R (Ω) of the impedance (see Equation 2), (c) the reflection coefficient Γ (see Equation 3), (d) the return loss RL (dB) (see Equation 4), and (e) the S-parameter S. 11 (dB) (see equation 5)

[0064]

[0065]

[0066]

[0067]

[0068]

[0069] In step ST16, it is determined whether a stop condition is satisfied. The stop condition may be a condition for determining whether RF reflection characteristics are obtained evenly across the range from the minimum frequency to the maximum frequency. For example, the stop condition may be a condition for determining whether the number of repetition cycles of steps ST10 to ST14 has reached a given number. Alternatively, the stop condition may be a condition for determining whether RF reflection characteristics are obtained for a low-power RF signal of a specific frequency. For example, if the frequency is increased stepwise from the minimum frequency to the maximum frequency in the repetition cycle of step ST10, the stop condition may be a condition for determining whether RF reflection characteristics are obtained for a low-power RF signal of the maximum frequency. If it is determined that the stop condition is not satisfied, the process returns to step ST10. If it is determined that the stop condition is satisfied, the process proceeds to step ST18.

[0070] In step ST18, the static characteristics are stored. Specifically, the RF reflection characteristics for each frequency acquired through the repeated cycle of steps ST10 to ST14 are stored as static characteristics in the memory unit 2a2 of the control unit 2.

[0071] 6 is a diagram showing an example of static characteristics. Fig. 6 shows an example in which the RF reflection characteristics acquired in step ST14 are S parameters. In Fig. 6, the horizontal axis represents frequency F [Hz], and the vertical axis represents S parameters S １１ In the example shown in FIG. 6, as shown by the dotted line in the figure, the S parameter S １１ A region where the S parameter S is significantly different from zero (characteristic RF reflection characteristics) appears at multiple frequencies between the minimum frequency (f_min) and the maximum frequency (f_max). １１ The greater the deviation from zero (the larger the absolute value), the smaller the return loss of the low-power RF signal. １１The frequency fa at which the return loss is smallest is the frequency fa at which the return loss is smallest. The static characteristics stored in the storage unit 2a2 may include information about the frequency fa at which the return loss is smallest.

[0072] The static characteristics may vary depending on the control conditions of the RF system. For example, changing the constant (reactance value) of the first matching circuit 34a may also vary the static characteristics. Therefore, the control conditions of the RF system may be changed to execute the static characteristics determination sequence, and the static characteristics for each control condition may be stored in the storage unit 2a2. For example, the reactance value of the first matching circuit 34a may be changed within a given range (e.g., in 10% increments), and the static characteristics determination sequence may be executed for each reactance value. In this case, the static characteristics for each reactance value of the first matching circuit 34a are stored in the storage unit 2a2.

[0073] In one embodiment, the static characterization sequence may be performed by providing a low-power RF signal from the second RF generator 31b with no plasma generated in the chamber 10.

[0074] In one embodiment, the static characteristic determination sequence may be executed by supplying a low-power RF signal from the second RF generator 31b while plasma is being generated in the chamber 10. For example, the static characteristic determination sequence shown in Fig. 5 may be executed while plasma is being generated in the chamber 10 by supplying a first RF signal (source RF signal) from the first RF generator 31a. In this case, the low-power RF signal supplied from the second RF generator 31b in step ST12 may have a power of less than 1 W, for example.

[0075] Conventionally, electrical characteristics of a chamber, such as RF reflection characteristics, have had to be measured by connecting a separate measuring device, such as a VNA (Vector Network Analyzer), to the chamber. However, when using a separate measuring device, there is a limit to the power of the signal supplied to the chamber (e.g., 1 mW or less). Furthermore, after the plasma processing apparatus is installed and operational, it is difficult to connect a separate measuring device to measure the electrical characteristics, and therefore, estimation calculations using an equivalent circuit have been required.

[0076] According to one embodiment, the electrical characteristics of the chamber 10 are measured by the RF system itself, eliminating the need to connect any other measuring equipment, and there are no limitations on the power of the RF signal supplied to the chamber 10, as described above. Furthermore, since the electrical characteristics can be measured in real time while the RF system is connected to the chamber 10, the measurement accuracy can be improved compared to estimation calculations using an equivalent circuit. Furthermore, since measurements can be performed periodically under the same conditions after the plasma processing apparatus 1 is installed and put into operation, it is also possible to acquire and analyze changes in the electrical characteristics over time.

[0077] <Example of Plasma Ignition Determination Sequence> Figure 7 is a flowchart showing an example of the plasma ignition determination sequence. As shown in Figure 7, the plasma ignition determination sequence may include step ST20 of supplying a source RF signal for plasma ignition (hereinafter also referred to as an "RF ignition signal") used to ignite plasma in chamber 10, step ST22 of acquiring RF reflection characteristics, step ST24 of comparing the RF reflection characteristics with static characteristics, and step ST26 of determining whether plasma has been ignited. Steps ST20 to ST26 may be performed periodically or continuously.

[0078] In step ST20, an RF ignition signal is supplied from the first RF generating unit 31a. The frequency of the RF ignition signal may be determined based on the static characteristics stored in the storage unit 2a2. For example, the frequency of the RF ignition signal may be selected based on the static characteristics at which the return loss is smallest (for example, frequency fa in the example shown in FIG. 6). Note that if multiple static characteristics are stored, the frequency may be determined based on the static characteristics under control conditions that are the same as or closest to the control conditions in step ST20 (for example, the reactance value of the first matching circuit 34a is the same as or closest to the control conditions in step ST20).

[0079] In step ST22, the RF reflection characteristic is acquired. Specifically, the first RF measurement unit 33a (see FIGS. 3 and 4) acquires the RF reflection characteristic of the first RF signal (RF ignition signal) propagating through the first transmission line TLa. A specific example of the RF reflection characteristic and a calculation method thereof may be the same as those in the static characteristic determination sequence (step ST14).

[0080] In step ST24, a comparison is made with the static characteristics (RF reflection characteristics when a low-power RF signal is supplied). Specifically, the difference between the RF reflection characteristics acquired in step ST22 and the static characteristics stored in memory unit 2a2 is calculated.

[0081] In step ST26, the plasma ignition state is determined. That is, if the difference between the RF reflection characteristic and the static characteristic is equal to or less than the threshold, it is determined that plasma is not ignited in the chamber 10 (plasma non-ignition state). In this case, step ST22 is executed again after a given period or continuously. On the other hand, if the difference between the RF reflection characteristic and the static characteristic is greater than the threshold, it is determined that plasma is ignited in the chamber 10 (plasma ignition state). In this case, the plasma ignition determination sequence is terminated, and the process proceeds to impedance matching operation using the first matching circuit 34a, and the matching operation is started. In the matching operation, for example, the reactance of the variable reactance element may be controlled so that the impedance seen from the input end of the first matching circuit 34a to the load side becomes a characteristic impedance (e.g., 50Ω).

[0082] Fig. 8 is a diagram illustrating an example of a plasma ignition determination sequence. In Fig. 8, the horizontal axis represents time t (sec) from the start of the plasma ignition determination sequence, and the vertical axis represents the resistance component R (Ω) of the impedance as an example of an RF reflection characteristic. In Fig. 8, Rm represents the RF reflection characteristic acquired in step ST22. Rs represents the static characteristic (the resistance component R of the impedance when a low-power RF signal is supplied) stored in memory unit 2a2.

[0083] 8, the difference between the RF reflection characteristic (Rm) and the static characteristic (R) is almost zero for a while after the start of the plasma ignition determination sequence, but at time t1, the difference between the two (R2-R1) suddenly increases and exceeds the threshold value. In the example shown in FIG. 8, it is determined that plasma has been ignited in chamber 10 at time t1.

[0084] As described above, by executing the plasma ignition determination sequence, it is possible to accurately and quickly determine whether or not plasma has been ignited in the chamber 10. This allows for a more precise transition from plasma ignition to impedance matching operation.

[0085] The present disclosure may be implemented in a plasma processing apparatus 1 using any plasma source, such as a capacitively coupled plasma source or a microwave plasma source, in addition to an inductively coupled plasma processing apparatus 1. For example, the static characteristic determination sequence and the plasma ignition determination sequence described above may be implemented in a capacitively coupled plasma processing apparatus. In this case, the capacitively coupled plasma processing apparatus includes an upper electrode and a lower electrode. The lower electrode is disposed within a substrate support, and the upper electrode is disposed above the substrate support. The first RF generator 31a is coupled to the upper electrode or the lower electrode via an impedance matching circuit, and the second RF generator 31b is coupled to the lower electrode via an impedance matching circuit. That is, the RF power supply 31 is coupled to the plasma processing chamber. In an inductively coupled plasma processing apparatus, coupling the RF power supply to the chamber includes electrically connecting the RF power supply to a bias electrode and / or an antenna.

[0086] Embodiments of the present disclosure further include the following aspects.

[0087] (Supplementary Note 1) A plasma processing apparatus comprising: a chamber; an RF power source coupled to the chamber; a measuring instrument configured to periodically or continuously determine an RF reflection characteristic at a node between the chamber and the RF power source; a memory unit configured to store a static characteristic, the static characteristic being an RF reflection characteristic at the node when a low-power RF signal is supplied to the chamber from the RF power source, the low-power RF signal having a power level that does not ignite plasma in the chamber; and a control unit configured to execute a plasma ignition determination sequence, the plasma ignition determination sequence including: comparing the periodically or continuously determined RF reflection characteristic with the static characteristic stored in the memory unit; determining that plasma has not been ignited in the chamber if a difference between the compared RF reflection characteristic and the static characteristic is equal to or less than a threshold; and determining that plasma has been ignited in the chamber if the difference between the compared RF reflection characteristic and the static characteristic is greater than a threshold.

[0088] 2. The plasma processing apparatus of claim 1, wherein the RF reflection characteristics are determined from voltages and currents sensed at the nodes.

[0089] (Supplementary Note 3) The plasma processing apparatus according to Supplementary Note 1 or Supplementary Note 2, wherein the static characteristics include RF reflection characteristics for each frequency of the low-power RF signal.

[0090] (Supplementary Note 4) The plasma processing apparatus according to any one of Supplementary Note 1 to Supplementary Note 3, wherein the RF reflection characteristics include one or more of the following at the node: (a) a power ratio between a forward wave and a reflected wave; (b) a resistance component of impedance (Ω); (c) a reflection coefficient; (d) a return loss (dB); and (e) an S-parameter (dB).

[0091] (Supplementary Note 5) The plasma processing apparatus according to any one of Supplementary Note 1 to Supplementary Note 4, further comprising an impedance matching circuit connected between the chamber and the measuring device.

[0092] (Supplementary Note 6) The plasma processing apparatus according to any one of Supplementary Note 1 to Supplementary Note 4, further comprising an impedance matching circuit connected between the RF power supply and the measuring device.

[0093] (Supplementary Note 7) The plasma processing apparatus of any one of Supplementary Notes 1 to 6, wherein the control unit is further configured to execute a static characteristic determination sequence, the control unit is further configured to execute a static characteristic determination sequence, the static characteristic determination sequence including: sequentially supplying a plurality of low-power RF signals from the RF power supply to the chamber, each of the plurality of low-power RF signals having a different frequency from one another; acquiring an RF reflection characteristic for each frequency in the measuring instrument; and storing the acquired RF reflection characteristic for each frequency in the memory unit as a static characteristic.

[0094] (Supplementary Note 8) The plasma processing apparatus of Supplementary Note 7, wherein the static characterization sequence is performed in a state where no plasma is generated in the chamber, and the low-power RF signal has a power of less than 10 W.

[0095] (Supplementary Note 9) The plasma processing apparatus of Supplementary Note 7, further comprising another RF power supply configured to generate a source RF signal to generate plasma in the chamber, wherein the static characterization sequence is performed while plasma is being generated in the chamber by the source RF signal supplied from the other RF power supply, and the low-power RF signal has a power of less than 1 W.

[0096] (Supplementary Note 10) The plasma processing apparatus according to any one of Supplementary Note 7 to Supplementary Note 9, wherein the static characteristic determination sequence is executed periodically based on an operating time of the RF power supply.

[0097] (Supplementary Note 11) The plasma processing apparatus according to any one of Supplementary Note 1 to Supplementary Note 10, wherein the control unit determines a frequency of an RF ignition signal used to ignite plasma in the chamber based on the static characteristics stored in the memory unit.

[0098] (Supplementary Note 12) The plasma processing apparatus according to Supplementary Note 11, wherein the frequency of the RF ignition signal is selected from one or more frequencies that exhibit a characteristic RF reflection characteristic in the static characteristics.

[0099] (Supplementary Note 13) The plasma processing apparatus according to Supplementary Note 5 or Supplementary Note 6, wherein the control unit is configured to transition to a matching operation using the impedance matching circuit when it is determined that plasma has been ignited in the chamber.

[0100] (Supplementary Note 14) A plasma processing apparatus comprising: a chamber; an RF power source coupled to the chamber; a measuring instrument configured to periodically or continuously determine an RF reflection characteristic at a node between the chamber and the RF power source; a memory unit; and a control unit configured to execute a static characteristic determination sequence, wherein the static characteristic determination sequence includes: sequentially supplying a plurality of low-power RF signals from the RF power source to the chamber, each of the plurality of low-power RF signals having a different frequency from each other and having a power level that does not ignite plasma in the chamber; acquiring an RF reflection characteristic for each frequency in the measuring instrument; and storing the acquired RF reflection characteristic for each frequency in the memory unit.

[0101] (Supplementary Note 15) The plasma processing apparatus of Supplementary Note 14, wherein the static characterization sequence is performed in a state where no plasma is generated in the chamber, and the low-power RF signal has a power of less than 10 W.

[0102] (Supplementary Note 16) The plasma processing apparatus of Supplementary Note 14, further comprising another RF power supply configured to generate a source RF signal to generate plasma in the chamber, wherein the static characterization sequence is performed while plasma is being generated in the chamber by the source RF signal supplied from the other RF power supply, and wherein the low-power RF signal has a power of less than 1 W.

[0103] (Supplementary Note 17) The plasma processing apparatus according to any one of Supplementary Note 14 to Supplementary Note 6, wherein the static characteristic determination sequence is executed periodically based on an operating time of the RF power supply.

[0104] (Supplementary Note 18) A plasma processing apparatus comprising: a chamber; an RF power supply coupled to the chamber; a measuring instrument configured to periodically or continuously determine an RF reflection characteristic at a node between the chamber and the RF power supply; a memory unit configured to store a static characteristic, the static characteristic being an RF reflection characteristic at the node when an RF signal is supplied to the chamber from the RF power supply under conditions in which plasma is not ignited; and a control unit configured to execute a plasma ignition determination sequence, wherein the plasma ignition determination sequence includes: comparing the periodically or continuously determined RF reflection characteristic with the static characteristic stored in the memory unit; determining that plasma has not been ignited in the chamber if a difference between the compared RF reflection characteristic and the static characteristic is equal to or less than a threshold; and determining that plasma has been ignited in the chamber if a difference between the compared RF reflection characteristic and the static characteristic is greater than a threshold.

[0105] (Supplementary Note 19) The plasma processing apparatus of Supplementary Note 18, wherein the control unit is further configured to execute a static characteristic determination sequence, and the static characteristic determination sequence includes: sequentially supplying a plurality of RF signals from the RF power supply to the chamber under conditions where plasma is not ignited, wherein each of the plurality of low-power RF signals has a different frequency; acquiring an RF reflection characteristic for each frequency in the measuring instrument; and storing the acquired RF reflection characteristic for each frequency in the memory unit as a static characteristic.

[0106] The above embodiments are described for the purpose of explanation and are not intended to limit the scope of the present disclosure. Various modifications can be made to the above embodiments without departing from the scope and spirit of the present disclosure. For example, some components in one embodiment can be added to other embodiments. Also, some components in one embodiment can be replaced with corresponding components in other embodiments.

[0107] REFERENCE SIGNS LIST 1: plasma processing apparatus, 2: control unit, 10: plasma processing chamber, 10s: plasma processing space, 31: RF power supply, 31a: first RF generating unit, 31b: second RF generating unit, 33a: first RF measuring unit, 33b: second RF measuring unit, 34a: first matching circuit, 34b: second matching circuit

Claims

1. A plasma processing apparatus comprising: a chamber; an RF power source coupled to the chamber; a measurement instrument configured to periodically or continuously determine an RF reflection characteristic at a node between the chamber and the RF power source; a memory configured to store a static characteristic, the static characteristic being an RF reflection characteristic at the node when a low-power RF signal is supplied to the chamber from the RF power source, the low-power RF signal having a power such that plasma is not ignited in the chamber; and a control unit configured to execute a plasma ignition determination sequence, the plasma ignition determination sequence comprising: comparing the periodically or continuously determined RF reflection characteristic with the static characteristic stored in the memory; determining that plasma has not been ignited in the chamber if a difference between the compared RF reflection characteristic and the static characteristic is equal to or less than a threshold; and determining that plasma has been ignited in the chamber if a difference between the compared RF reflection characteristic and the static characteristic is greater than a threshold.

2. The plasma processing apparatus of claim 1, wherein the RF reflection characteristics are determined from voltages and currents sensed at the nodes.

3. The plasma processing apparatus of claim 1, wherein the static characteristics include an RF reflection characteristic for each frequency of the low-power RF signal.

4. The plasma processing apparatus of claim 3, wherein the RF reflection characteristics include one or more of the following at the node: (a) power ratio of forward wave to reflected wave; (b) resistive component of impedance (Ω); (c) reflection coefficient; (d) return loss (dB); and (e) S-parameter (dB).

5. The plasma processing apparatus of claim 1, further comprising an impedance matching circuit connected between said chamber and said measurement instrument.

6. The plasma processing apparatus of claim 1, further comprising an impedance matching circuit connected between said RF power source and said measurement instrument.

7. A plasma processing apparatus as described in any one of claims 1 to 6, wherein the control unit is further configured to execute a static characteristic determination sequence, the static characteristic determination sequence including: sequentially supplying a plurality of low-power RF signals from the RF power supply to the chamber, each of the plurality of low-power RF signals having a different frequency from one another; acquiring an RF reflection characteristic for each frequency in the measuring instrument; and storing the acquired RF reflection characteristic for each frequency in the memory unit as a static characteristic.

8. The plasma processing apparatus of claim 7, wherein the static characterization sequence is performed with no plasma generated in the chamber, and the low-power RF signal has a power of less than 10 W.

9. The plasma processing apparatus of claim 7, further comprising: another RF power supply configured to generate a source RF signal to generate plasma in the chamber; and the static characterization sequence is performed in a state in which plasma is generated in the chamber by the source RF signal supplied from the other RF power supply; and the low-power RF signal has a power of less than 1 W.

10. The plasma processing apparatus of claim 7, wherein the static characterization sequence is performed periodically based on an operating time of the RF power supply.

11. The plasma processing apparatus of claim 3 or 4, wherein the control unit determines the frequency of an RF ignition signal used to ignite plasma in the chamber based on the static characteristics stored in the memory unit.

12. The plasma processing apparatus of claim 11, wherein the frequency of the RF ignition signal is selected from one or more frequencies that exhibit characteristic RF reflection characteristics in the static characteristic.

13. A plasma processing apparatus as described in claim 5 or 6, wherein the control unit is configured to transition to a matching operation using the impedance matching circuit when it is determined that plasma has been ignited in the chamber.

14. A plasma processing apparatus comprising: a chamber; an RF power source coupled to the chamber; a measuring device configured to periodically or continuously determine an RF reflection characteristic at a node between the chamber and the RF power source; a memory unit; and a control unit configured to execute a static characteristic determination sequence, the static characteristic determination sequence including: sequentially supplying a plurality of low-power RF signals from the RF power source to the chamber, each of the plurality of low-power RF signals having a different frequency from each other and having a power sufficient to not ignite plasma in the chamber; acquiring an RF reflection characteristic for each frequency in the measuring device; and storing the acquired RF reflection characteristic for each frequency in the memory unit.

15. The plasma processing apparatus of claim 14, wherein the static characterization sequence is performed with no plasma generated in the chamber, and the low-power RF signal has a power less than 10 W.

16. The plasma processing apparatus of claim 14, further comprising: another RF power supply configured to generate a source RF signal to generate plasma in the chamber; and the static characterization sequence is performed in a state in which plasma is generated in the chamber by the source RF signal provided by the other RF power supply; and the low-power RF signal has a power of less than 1 W.

17. The plasma processing apparatus of claim 14, wherein the static characterization sequence is performed periodically based on an operating time of the RF power supply.

18. A plasma processing apparatus comprising: a chamber; an RF power source coupled to the chamber; a measuring instrument configured to periodically or continuously determine an RF reflection characteristic at a node between the chamber and the RF power source; a memory unit configured to store a static characteristic, the static characteristic being an RF reflection characteristic at the node when an RF signal is supplied to the chamber from the RF power source under a condition in which plasma is not ignited; and a control unit configured to execute a plasma ignition determination sequence, the plasma ignition determination sequence including: comparing the periodically or continuously determined RF reflection characteristic with the static characteristic stored in the memory unit; determining that plasma has not been ignited in the chamber if a difference between the compared RF reflection characteristic and the static characteristic is equal to or less than a threshold; and determining that plasma has been ignited in the chamber if a difference between the compared RF reflection characteristic and the static characteristic is greater than a threshold.

19. The plasma processing apparatus of claim 18, wherein the control unit is further configured to execute a static characteristic determination sequence, the static characteristic determination sequence including: sequentially supplying a plurality of RF signals from the RF power supply to the chamber under conditions in which plasma is not ignited, each of the plurality of low-power RF signals having a different frequency from one another; acquiring an RF reflection characteristic for each frequency in the measuring instrument; and storing the acquired RF reflection characteristic for each frequency in the memory unit as a static characteristic.

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