Plasma measurement method and plasma measurement system

Abstract

The present invention provides a plasma measurement method for measuring the state of a plasma, and a plasma measurement method. [Solution] A plasma measurement method comprising: a step of supplying a fixed alternating current to the plasma via the probe device while plasma is generated in the plasma processing apparatus in an initial state in which no conductive deposited film is deposited on the surface of the probe device, and measuring the initial state plasma voltage with the measurement circuit; a step of supplying a fixed alternating current to the plasma via the probe device while plasma is generated in the plasma processing apparatus in an operating state in which the conductive deposited film is deposited on the surface of the probe device, and measuring the operating state measurement voltage with the measurement circuit; a step of subtracting the initial state plasma voltage from the measurement voltage to derive the conductive deposited film voltage; and a step of deriving the plasma state using the plasma voltage obtained by subtracting the conductive deposited film voltage from the measurement voltage.

Description

[Technical Field]

[0001] This disclosure relates to a plasma measurement method and a plasma measurement system. [Background technology]

[0002] Patent Document 1 discloses a plasma probe device comprising: an antenna portion attached to an opening formed in the wall or mounting base of a processing container via a sealing member that seals the space between a vacuum space and an atmospheric space; an electrode connected to the antenna portion; and a dielectric support portion formed of a dielectric material that supports the antenna portion from the surroundings, wherein the opposing surfaces of the antenna portion and the wall or mounting base are separated by a predetermined width, and the surface of the antenna portion exposed from the opening is recessed compared to the surface of the wall or mounting base on the plasma generation space side in which the opening is formed. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-46787 [Overview of the project] [Problems that the invention aims to solve]

[0004] In one aspect, this disclosure provides a plasma measurement method and a plasma measurement system for measuring the state of a plasma. [Means for solving the problem]

[0005] To solve the above problems, according to one embodiment, a plasma measurement method is provided for measuring the state of a plasma using a probe device provided in a plasma processing apparatus and a measurement circuit including a signal generator that outputs a fixed alternating current, the method comprising: a step of supplying the fixed alternating current to the plasma via the probe device when plasma is generated in the plasma processing apparatus in an initial state in which no conductive deposited film is deposited on the surface of the probe device, and measuring the initial state plasma voltage with the measurement circuit; a step of supplying the fixed alternating current to the plasma via the probe device when plasma is generated in the plasma processing apparatus in an operating state in which the conductive deposited film is deposited on the surface of the probe device, and measuring the operating state measurement voltage with the measurement circuit; a step of subtracting the initial state plasma voltage from the measurement voltage to derive the conductive deposited film voltage; and a step of deriving the state of the plasma using the plasma voltage obtained by subtracting the conductive deposited film voltage from the measurement voltage. [Effects of the Invention]

[0006] In one aspect, it is possible to provide a plasma measurement method and a plasma measurement system for measuring the state of a plasma. [Brief explanation of the drawing]

[0007] [Figure 1] A schematic cross-sectional view showing an example of a plasma processing apparatus according to one embodiment. [Figure 2] Figure 1 shows an example of a cross-section AA. [Figure 3] A diagram showing an example of the functional configuration of a measurement system and control device according to one embodiment. [Figure 4] A flowchart illustrating an example of a control method for a plasma processing device. [Figure 5] A graph showing an example of a received signal from the plasma side. [Figure 6] An example of a circuit model for a measurement system. [Figure 7] An example of a circuit model for a measurement system that includes parasitic capacitance. [Figure 8] An example of a vector diagram showing current and voltage vectors. [Figure 9] An example of a circuit model for a measurement system in the case of a second harmonic. [Figure 10] An example of a vector diagram showing current and voltage vectors. [Figure 11] A diagram showing an example of a circuit model of deposits in a probe device. [Figure 12] Another example of a measurement system circuit model. [Figure 13] An example flowchart illustrating the method for deriving the plasma state. [Modes for carrying out the invention]

[0008] The following describes embodiments for implementing this disclosure with reference to the drawings. In each drawing, the same reference numerals are used for identical components, and redundant explanations may be omitted.

[0009] [Plasma treatment device] Figure 1 shows an example of a cross-sectional view of a plasma processing apparatus 100 according to one embodiment of the present invention. The plasma processing apparatus 100 has a processing container 1 that accommodates a substrate W, such as a semiconductor wafer. The plasma processing apparatus 100 is an example of a plasma processing apparatus that performs plasma processing on the substrate W using surface wave plasma formed on the lower surface of the top wall 10 of the processing container 1 by microwaves. Examples of plasma processing include film deposition, etching, or ashing using plasma.

[0010] The plasma processing apparatus 100 comprises a processing vessel 1, a microwave plasma source 2, and a control device 3. The processing vessel 1 is a substantially cylindrical container made of a metal material such as aluminum or stainless steel, which is airtight and grounded.

[0011] The processing container 1 has a top wall 10 and forms a space (plasma generation space U) inside for plasma processing of the substrate W. The top wall 10 is disc-shaped and is a lid that closes the upper opening of the processing container 1. A support ring 129 is provided at the contact surface between the processing container 1 and the top wall 10, thereby sealing the inside of the processing container 1 airtight. The top wall 10 is made of a metal material such as aluminum or stainless steel.

[0012] The microwave plasma source 2 comprises a microwave output unit 30, a microwave transmission unit 40, and a microwave radiation mechanism 50. The microwave output unit 30 outputs microwaves by distributing them through multiple paths. The microwaves are introduced into the processing container 1 through the microwave transmission unit 40 and the microwave radiation mechanism 50. The gas supplied into the processing container 1 is excited by the electric field of the introduced microwaves, thereby forming a surface wave plasma.

[0013] A mounting table 11 for placing the substrate W is provided inside the processing container 1. The mounting table 11 is supported by a cylindrical support member 12 erected at the center of the bottom of the processing container 1 via an insulating member 12a. Examples of materials constituting the mounting table 11 and the support member 12 include metals such as aluminum with anodized (anodic oxidation) surfaces, and insulating materials (ceramics, etc.) having high-frequency electrodes inside. The mounting table 11 may be provided with an electrostatic chuck for electrostatically adsorbing the substrate W, a temperature control mechanism, a gas channel for supplying heat transfer gas to the back surface of the substrate W, and the like.

[0014] A high-frequency bias power supply 14 is connected to the mounting stage 11 via a matching unit 13. High-frequency power is supplied from the high-frequency bias power supply 14 to the mounting stage 11, drawing ions from the plasma towards the substrate W. Note that the high-frequency bias power supply 14 may not be necessary depending on the characteristics of the plasma processing.

[0015] An exhaust pipe 15 is connected to the bottom of the processing container 1, and an exhaust device 16, including a vacuum pump, is connected to the exhaust pipe 15. When the exhaust device 16 is activated, the inside of the processing container 1 is evacuated, thereby rapidly reducing the pressure inside the processing container 1 to a predetermined vacuum level. An inlet / outlet 17 for loading and unloading substrates W and a gate valve 18 for opening and closing the inlet / outlet 17 are provided on the side wall of the processing container 1.

[0016] The microwave transmission unit 40 transmits microwaves output from the microwave output unit 30. Figure 2 shows a cross-section AA of Figure 1 and an example of the lower surface of the top wall of the plasma processing apparatus 100. Referring to Figure 2, the central microwave introduction unit 43b in the microwave transmission unit 40 is located in the center of the top wall 10, and the six peripheral microwave introduction units 43a are arranged at equal intervals in the circumferential direction around the top wall 10. The central microwave introduction unit 43b and the six peripheral microwave introduction units 43a each have the function of introducing microwaves output from the amplifier unit 42 shown in Figure 1 into the microwave radiation mechanism 50 and the function of matching impedance. Hereinafter, the peripheral microwave introduction units 43a and the central microwave introduction unit 43b will be collectively referred to as the microwave introduction unit 43.

[0017] As shown in Figures 1 and 2, the six dielectric windows 123 on the outer periphery are located inside the top wall 10 below the six peripheral microwave introduction sections 43a. The central dielectric window 133 is located inside the top wall 10 below the central microwave introduction section 43b. The number of peripheral microwave introduction sections 43a and dielectric windows 123 is not limited to six, but can be two or more. However, the number of peripheral microwave introduction sections 43a is preferably three or more, and may be, for example, three to six.

[0018] The microwave radiation mechanism 50 shown in Figure 1 has slow-wave plates 121, 131, slots 122, 132, and dielectric windows 123, 133. The slow-wave plates 121, 131 are formed from disc-shaped dielectrics that transmit microwaves and are placed on the upper surface of the top wall 10. The slow-wave plates 121, 131 are made of ceramics such as quartz and alumina (Al2O3), or fluororesins such as polytetrafluoroethylene or polyimide resins, which have a relative permittivity greater than that of a vacuum. This makes the wavelength of microwaves passing through the slow-wave plates 121, 131 shorter than the wavelength of microwaves propagating in a vacuum, thereby reducing the size of the antenna including the slots 122, 132.

[0019] Below the slow-wave plates 121 and 131, dielectric windows 123 and 133 are in contact with the back surface of the opening in the ceiling wall 10 via slots 122 and 132 formed in the ceiling wall 10. The dielectric windows 123 and 133 are formed of, for example, ceramics such as quartz and alumina (Al2O3), fluororesins such as polytetrafluoroethylene, or polyimide resins. The dielectric windows 123 and 133 are positioned recessed from the ceiling surface by the thickness of the opening formed in the ceiling wall 10, and supply microwaves to the plasma generation space U.

[0020] The peripheral microwave introduction section 43a and the central microwave introduction section 43b have a cylindrical outer conductor 52 and a rod-shaped inner conductor 53 located at its center arranged coaxially. Microwave power is supplied between the outer conductor 52 and the inner conductor 53, forming a microwave transmission path 44 through which microwaves propagate toward the microwave radiation mechanism 50.

[0021] The peripheral microwave introduction section 43a and the central microwave introduction section 43b are provided with a slug 54 and an impedance adjustment member 140 located at its tip. By moving the slug 54, the impedance of the load (plasma) in the processing container 1 is matched to the characteristic impedance of the microwave power supply in the microwave output section 30. The impedance adjustment member 140 is made of a dielectric material and adjusts the impedance of the microwave transmission line 44 according to its relative permittivity.

[0022] A shower-type gas introduction section 21 is provided on the top wall 10. Gas supplied from the gas supply source 22 is supplied in a shower-like manner into the processing container 1 via the gas supply piping 111, passing from the gas diffusion chamber 62 through the gas introduction section 21. The gas introduction section 21 is an example of a gas showerhead that supplies gas from a plurality of gas supply holes 60 formed in the top wall 10. Examples of gases include plasma generation gases such as Ar gas, gases to be decomposed with high energy such as O2 gas and N2 gas, and processing gases such as silane gas.

[0023] Each part of the plasma processing apparatus 100 is controlled by the control device 3. The control device 3 includes a microprocessor 4, a ROM (Read Only Memory) 5, and a RAM (Random Access Memory) 6. The ROM 5 and RAM 6 store the process sequence and process recipe, which are the control parameters of the plasma processing apparatus 100. The microprocessor 4 controls each part of the plasma processing apparatus 100 based on the process sequence and process recipe. The control device 3 also has a communication interface (I / F) 7, enabling communication with other devices. Furthermore, the control device 3 has a display 8, which can display the results of predetermined control operations performed according to the process sequence and process recipe.

[0024] When performing plasma processing in the plasma processing apparatus 100 with the above configuration, first, the substrate W is carried into the processing container 1 through the opening gate valve 18 and the loading port 17 while being held on a transport arm (not shown). When the substrate W is transported to above the mounting table 11, it is transferred from the transport arm to a pusher pin, and the pusher pin descends to place it on the mounting table 11. The gate valve 18 is closed after the substrate W has been loaded. The pressure inside the processing container 1 is maintained at a predetermined vacuum level by the exhaust device 16. Processing gas is introduced into the processing container 1 in a shower-like manner from the gas introduction section 21. Microwaves emitted from the microwave radiation mechanism 50 via the microwave introduction section 43 propagate near the bottom surface, which is the inner surface of the top wall 10. The electric field of the surface wave microwaves excites the gas, and the substrate W is subjected to plasma processing by the surface wave plasma generated in the plasma generation space U below the top wall 10 inside the processing container 1.

[0025] [Probe device] The description of the probe device 70 will continue with reference to Figures 1 and 3. Figure 3 is a diagram showing an example of the functional configuration of a measurement system and control device according to one embodiment. As shown in Figure 1, one or more openings 1b are formed in the circumferential direction on the side wall of the processing container 1, and one or more probe devices 70 are attached via sealing members (not shown) that seal the space between the vacuum space and the atmospheric space.

[0026] A gap of a predetermined width is formed between the tip surface of the probe device 70 and the back surface near the opening 1b in the wall of the processing container 1. This gap is designed to be wide enough so that the probe device 70 is not DC-connected to the wall of the processing container 1, but narrow enough so that plasma or gas does not enter. However, the probe device 70 may also be attached to the mounting base 11 via a sealing member through an opening formed therein.

[0027] As shown in Figure 3, the measurement system for measuring the plasma state consists of a probe device 70 and a measurement circuit 85. The measurement circuit 85 includes a monitor device 80, a blocking capacitor 72, and a coaxial cable 81. The monitor device 80 is communicated to the control device 3.

[0028] The probe device 70 is connected to the monitor device 80 via a coaxial cable 81 outside the plasma processing device 100. The monitor device 80 has a signal transmitter 82, which outputs an AC voltage signal of a predetermined frequency to the coaxial cable 81. The AC voltage signal is transmitted through the coaxial cable 81, and the AC voltage is applied to the probe device 70. A blocking capacitor 72 is connected to the coaxial cable 81 and transmits the AC voltage signal to the probe device 70, blocking the DC voltage signal. As a result, the monitor device 80 receives only the AC voltage signal from the plasma side.

[0029] The probe device 70 senses the plasma generated in the plasma generation space U. The probe device 70 detects the current signal flowing to the plasma side in response to the signal transmitted to the plasma side and transmits it to the monitor device 80. The current signal flowing to the plasma side is transmitted from the monitor device 80 to the control device 3 and received by the communication unit 32 of the control device 3. The current value of the received signal is stored in the storage unit 31. The analysis unit 34 of the control unit 33 performs an FFT (Fast Fourier Transform) analysis on the current value of the received signal. The calculation unit 35 of the control unit 33 calculates the plasma electron temperature T based on the analysis results. e or plasma ion density n i This calculates the plasma state, allowing for accurate estimation. Thus, the plasma measurement system for measuring the plasma state includes a probe device 70, a measurement circuit 85, and a control device 3 (control unit 33).

[0030] The memory unit 31 is implemented by the RAM 6 shown in Figure 1. The communication unit 32 is implemented by the communication interface 7. The analysis unit 34 and calculation unit 35 of the control unit 33 are implemented by the microprocessor 4.

[0031] Figure 4 is a flowchart showing an example of a control method for the plasma processing apparatus 100.

[0032] In step S101, substrate processing is performed. Here, the control device 3 controls the gas supply source 22 to supply processing gas (film deposition gas, etching gas, etc.) from the gas supply hole 60 to the plasma generation space U, and controls the microwave output unit 30 and the high-frequency bias power supply 14 to generate plasma of the processing gas in the plasma generation space U, and performs the desired processing (film deposition processing, etching processing, etc.) on the substrate W. At this time, the probe device 70 receives an AC voltage from the signal transmitter 82 and senses the plasma generated in the plasma generation space U. The control unit 33 then controls the plasma electron temperature T e or plasma ion density n i This is calculated to estimate the plasma state.

[0033] In this case, if the substrate processing is a process of forming an insulating film on the substrate W, an insulator (e.g., SiN, SiO2, etc.) is deposited on the surface of the probe device 70 that is exposed to the plasma generation space U (e.g., the tip surface of the probe device 70) to form an insulating film. Note that the substrate processing is not limited to the deposition of an insulating film, but may also be a process (e.g., etching) in which an insulator is formed as a reaction byproduct and the reaction byproduct (insulator) is deposited on the surface of the probe device 70 that is exposed to the plasma generation space U to form an insulating film.

[0034] In step S101, the substrate processing is repeated until the predetermined number of substrates to be processed, processing time, and other cleaning start conditions are met. Once the predetermined cleaning start conditions are met, the control device 3 proceeds to step S102.

[0035] In step S102, a cleaning process (dry cleaning process: a cleaning process using a cleaning gas without opening the processing container to the atmosphere) is performed. Here, the control device 3 controls the gas supply source 22 to supply a cleaning gas containing fluorine (F) (e.g., NF3) from the gas supply hole 60 to the plasma generation space U, and controls the microwave output unit 30 and / or the high-frequency bias power supply 14 to generate a plasma of the cleaning gas in the plasma generation space U, thereby removing the insulating film deposited inside the processing container 1. In addition, the insulating film deposited on the surface of the probe device 70 that is exposed to the plasma generation space U is also removed.

[0036] In the cleaning process, conductive fluoride adheres to and deposits on the surface of the probe device 70 that is exposed to the plasma generation space U, forming a conductive deposited film. The conductive fluoride is, for example, a metallic fluoride (e.g., AlF) containing metal (e.g., Al) derived from the inner wall of the processing container 1, dielectric windows 123 and 133 formed of alumina (Al2O3), etc., and fluorine (F) derived from the cleaning gas. The deposited metallic fluoride is conductive due to having lattice defects.

[0037] In step S103, it is determined whether or not to terminate the repetition. If the repetition is not terminated (S103 - NO), the control device 3 returns to step S101 and repeats the substrate processing and cleaning process. If the repetition is terminated (S103 - YES), the control device 3 terminates its processing. In addition, cleaning processes (wet cleaning: cleaning process with the processing container open to the atmosphere) are performed.

[0038] Here, we will describe an example of plasma state measurement. Figure 5 is a graph showing an example of a received signal from the plasma side.

[0039] FIG. 5(a) is a graph showing an example of raw data of a received signal detected by the probe device 70 and received by the monitor device 80. The horizontal axis represents time, and the vertical axis represents the intensity (current value) of the received signal. As shown in FIG. 5(a), the monitor device 80 receives the received signal 200 from the probe device 70.

[0040] FIG. 5(b) is a graph showing an example of the analysis result of the analysis unit 34 of the control unit 33. The analysis unit 34 performs FFT (Fast Fourier Transform) analysis on the current value of the received signal 200. As a result, the received signal 200 is decomposed into frequency components such as a fundamental wave component (first harmonic component) 201, a second harmonic component 202, a third harmonic component 203, a fourth harmonic component 204, and the like. Then, the calculation unit 35 of the control unit 33 calculates the plasma electron temperature T e and the plasma ion density n i based on the FFT analysis result. Thereby, the plasma state is measured. Note that the plasma electron temperature T e and the plasma ion density n i are calculated based on the fundamental wave component 201 and the second harmonic component 202, as will be described later.

[0041] [Method for Measuring Plasma State] Next, the measurement methods for the plasma electron temperature T e and the plasma ion density n i will be described using FIG. 6. FIG. 6 is an example of a circuit model of the measurement system.

[0042] As shown in FIG. 6, an insulating film is deposited on the probe device 70, so that it has a capacitance component C. Let the voltage of the insulating film (capacitance component C) be V c , and the voltage of the plasma be V p . Further, the monitor device 80 has a voltage measurement unit (not shown) for measuring the voltage (output terminal AC voltage) supplied to the plasma at the output terminal of the signal transmitter 82 and a current measurement unit (not shown) for measuring the current. Note that R0 is a resistor for measuring the current, the resistance value of which is known and is sufficiently small compared to the resistance value of the plasma. By measuring the voltage across both ends of R0, the current supplied to the plasma is measured.

[0043] Here, assuming the plasma is purely resistive (phase difference 0°), and the insulating film has a capacitive component C with a phase difference of 90°, the thickness of the insulating film (capacitive component C) and the state of the plasma (plasma electron temperature T) are related. e Plasma ion density n i ) and can be estimated separately.

[0044] The current I flowing through the circuit model is equal to the plasma voltage V. p It can be expressed using the following formula. Note that I is This is the ion saturation current, and I es V is the electron saturation current, f is a floating voltage, and φ p This is the plasma voltage, and T e This is the plasma electron temperature (in eV units), and n e n is the plasma electron density, i is the plasma ion density, and S is the probe area. Also, M i This is the ion mass (in kg), and m e This is the electron mass (in kg).

[0045]

number

[0046] Next, V p Let V0 = Acosωt. A is the amplitude of the AC voltage output by the signal generator 82. The equation for the current I flowing through the circuit model described above is given by the modified Bessel function of the first kind I. k We transform the equation using (x). This allows us to decompose the equation for current I into its frequency components.

[0047]

number

[0048] Here, the plasma electron density n e The information is the coefficient (I) of each frequency component. es It is included only in ). Therefore, the fundamental wave current i 1ωThe second harmonic current i 2ω By dividing by n, the plasma electron density n can be found in the formula. e Delete.

[0049]

number

[0050] From the above equation, the plasma electron temperature T e Calculate.

[0051] Also, plasma ion density n i This can be expressed by the following equation. The following equation and the calculated plasma electron temperature T e And the fundamental wave current i 1ω By using this, the plasma ion density n i It is possible to calculate this.

[0052]

number

[0053] [Method for measuring plasma state considering parasitic capacity] Figure 7 shows an example of a circuit model of a measurement system including parasitic capacitance (stray capacitance). Figure 8 shows an example of a vector diagram illustrating current and voltage vectors.

[0054] Voltage V total This is the voltage measured by the voltage measuring unit (not shown) of the monitoring device 80. Current I total This is the current measured by the current measuring unit (not shown) of the monitoring device 80. Voltage V plasma This is the plasma voltage. Current I plasma This is the plasma current. Voltage V plasma and current I plasma This refers to the state of the plasma (plasma electron temperature T e Plasma ion density n i It is used when measuring ( ).

[0055] Here, the circuit includes a series capacitor C in series with the signal oscillator 82.add , a parasitic capacitance C in parallel with the signal transmitter 82 stray This includes the state of the plasma (plasma electron temperature T). e Plasma ion density n i The plasma voltage V used when measuring ) plasma and current I plasma And the voltage V measured by the monitoring device 80 total and current I total A discrepancy arises between them.

[0056] Parasitic capacitance C in parallel with signal transmitter 82 stray The dominant component is the capacitance present on the circuit, such as the coaxial cable 81, which flows to the ground voltage (GND). Therefore, it occurs regardless of the presence or absence of plasma. Thus, in the plasma extinguished state, the current I measured by the current measuring unit (not shown) of the monitoring device 80 total From current I stray Measure.

[0057] Then, in the plasma ignition state, as shown in Figure 8(a), current I total is current I plasma and current I stray It is expressed as a vector sum. Therefore, the current I measured by the current measuring unit (not shown) of the monitoring device 80 total The current I measured beforehand from the current vector stray By calculating the current vector difference obtained by subtracting the current vector, the plasma current I plasma The current vector can be calculated.

[0058] A series capacitor C connected in series with the signal transmitter 82. add This represents the series capacitance component of the insulating film (SiN, etc.) formed by the capacitor and deposits placed in the probe device 70 for insulation, and current I plasma When it flows, current I plasma Voltage V, which is 90 degrees delayed. add This occurs. Note that parallel parasitic capacities C stray The effect on the plasma is assumed to be sufficiently small. Also, the plasma voltage V plasma and current I plasmaAssume that they are in phase.

[0059] As shown in Figure 8(b), the voltage V total is the voltage V plasma and voltage V add It is expressed as a vector sum of V. Therefore, the voltage V plasma and voltage V total Using the phase difference θ, Voltage V plasma =V total ×cosθ It can be calculated using this method.

[0060] Thus, the calculation unit 35 calculates the measured voltage V total and current I total Therefore, series capacitance C add and parasitic capacity C stray The deviation caused by this is corrected (calibrated), and the plasma voltage V plasma and current I plasma This allows for accurate calculation of the plasma state (plasma electron temperature T). e Plasma ion density n i ) can be measured with high accuracy.

[0061] [2nd harmonic current] The nonlinear current generated in the plasma creates a higher-order voltage in the capacitor inserted into the measurement system's circuit model. As a result, higher-order currents are superimposed on the plasma (see Figure 5). Similar to the case of the fundamental wave (first harmonic) explained using Figures 7 and 8, this component can be corrected (calibrated) by measuring the phase between the fundamental wave and the second harmonic current, since the total higher-order current vector and the generated higher-order current vector are orthogonal.

[0062] The following explains second harmonic current. Figure 9 shows an example of a circuit model of a measurement system for second harmonic current. Figure 10 shows an example of a vector diagram illustrating current and voltage vectors.

[0063] Voltage V plasma is the voltage V total (See Figure 7) add and voltage Vplasma is the voltage divided, provided that the voltage V plasma is only the fundamental wave voltage. That is, the signal generator 82 outputs the fundamental wave voltage. Therefore, in the circuit model of the measurement system in the second harmonic shown in FIG. 9, the signal generator 82 is not provided.

[0064] Voltage V 2,plasma is the second harmonic voltage applied to the plasma necessary for flowing the current I 2,cancel described later through the plasma.

[0065] Current I 2,plasma is the second harmonic current derived by applying the voltage V plasma to the plasma. This is generated because the current response in the plasma is non-linear.

[0066] Voltage V 2,plasma,add is the second harmonic current generated by flowing the current I<00​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​2,cancel =V 2,cancel / (1 / iωC add +R p ) =-I 2,plasma ×(1 / iωC add ) / (1 / iωC add +R p )

[0069] current I 2,total This is the amount of second-harmonic current flowing throughout the entire circuit, and current I 2,plasma and current I 2,cancel This is the sum of the two. That is, current I 2,total This can be expressed by the following formula. I 2,total =I 2,plasma +I 2,cancel =I 2,plasma ×(R p ) / (1 / iωC add +R p )

[0070] Here, current I 2,total is current I 2,plasma Since this corresponds to the real part when expressed in complex space, it can be expressed by the following equation. I 2,plasma =I 2,total / cosθ

[0071] Here, current I 2,plasma This is the fundamental wave voltage V calculated using the formula mentioned above. plasma This is the second harmonic current generated by [the process]. Therefore, the second harmonic current I 2,plasma This is the fundamental wave current I plasma This is in phase with the fundamental wave current. Therefore, the phase θ represents the phase difference between the phase of the fundamental wave current and the phase difference between the phase of the second harmonic current and the fundamental wave current.

[0072] Also, I 2,total =I 2,plasma +I 2,cancel I 2,total (1 / iωC add +R p )=(I 2,plasma +I 2,cancel )(1 / iωC add+R p ) I 2,total (1 / iωC add +R p )=I 2,plasma ×R p Thus, the current I 2,total is current I 2,cancel and current I 2,plasma This indicates that the currents cancel each other out. p / (1 / iωC add +R p ) is current I 2,plasma Current I 2,total This represents the cosine of the current I with respect to the phase angle θ. 2,plasma The plasma voltage V plasma It is in phase with the fundamental wave current I.

[0073] As described above, by accurately determining the fundamental wave current and the second harmonic current, the state of the plasma (plasma electron temperature T) can be determined. e Plasma ion density n i ) can be calculated with high accuracy.

[0074] [Control for conductive deposits] Figure 11 shows an example of a circuit model of the deposits in the probe device 70. Figure 12 shows another example of a circuit model of the measurement system.

[0075] Here, as shown in Figure 4, by performing substrate processing and cleaning (dry cleaning), a conductive deposited film (conductive fluoride, metal fluoride, AlF), an insulating film (e.g., SiN film), etc., is deposited on the surface of the probe device 70. Furthermore, the impedance component originating from the conductive deposited film has a resistive component and a capacitive component connected in parallel. Also, the impedance component originating from the insulating film has a capacitive component.

[0076] Specifically, on the surface of the probe device 70, conductive deposited films deposited during the cleaning process and insulating films that could not be completely removed during the cleaning process are deposited alternately, and further insulating films deposited after the cleaning process are deposited. Therefore, as shown in Figure 11(a), the circuit model consists of impedance components 701 derived from the conductive deposited film and impedance components 702 derived from the insulating film arranged alternately in series. Furthermore, the circuit model shown in Figure 11(a) can be converted into an equivalent model in which a capacitive component C and a resistive component R are arranged in series, as shown in Figure 11(b).

[0077] Therefore, as shown in Figure 12, in the circuit model for plasma measurement using the probe device 70, a capacitive component C and a resistive component R are added in series with the plasma by the deposition of an insulating film or a conductive deposited film on the surface of the probe device 70. The resistive component R changes depending on the deposition state of the conductive deposited film. The capacitive component C also changes depending on the deposition state of the insulating film or the conductive deposited film.

[0078] Here, the voltage across the capacitive component C is V. c Let the voltage across the resistive component R be V r Let the plasma voltage be V p The monitoring device 80 also includes a voltage measuring unit (not shown) for measuring the voltage supplied to the plasma from the signal transmitter 82 and a current measuring unit (not shown) for measuring the current. R0 is a resistor for measuring the current, and its resistance value is known and is sufficiently small compared to the resistance value of the plasma.

[0079] Here, assuming the plasma is a pure resistive with a phase difference of 0°, and the insulating film has a capacitive component C with a phase difference of 90°, the thickness of the insulating film (capacitive component C) and the state of the plasma (plasma electron temperature T) are related. e Plasma ion density n i ) and can be estimated separately. On the other hand, the resistive component R is placed in series with the plasma, and the voltage V of the resistive component R r and the plasma voltage V p It is difficult to separate them.

[0080] Therefore, a conductive deposited film is deposited on the surface of the probe device 70, which allows the plasma voltage V to be deposited. p The measurement accuracy decreases, and the plasma state (plasma electron temperature T) e Plasma ion density n i The estimation accuracy of the plasma electron temperature Te may decrease. For example, repeated substrate processing and cleaning processes may cause a conductive deposited film to accumulate on the surface of the probe device 70, potentially leading to an estimated plasma electron temperature Te being higher than the actual plasma electron temperature Te. Furthermore, as the amount of conductive deposited film on the surface of the probe device 70 increases, the estimated plasma electron temperature Te will rise, increasing the difference with the actual plasma electron temperature Te and potentially reducing the estimation accuracy of the plasma electron temperature Te.

[0081] Figure 13 is an example of a flowchart illustrating the method for deriving the plasma state. Here, even when a conductive deposited film is deposited on the surface of the probe device 70, the plasma voltage V can be accurately determined. p This is derived by controlling the plasma voltage to be constant by keeping the current flowing through the plasma constant.

[0082] In step S201, the surface of the probe device 70 is set to its initial state. Here, the initial state is a state in which no conductive deposited film has accumulated on the surface of the probe device 70. Specifically, the initial state may be a state in which a new probe device 70 has been installed. Alternatively, the initial state may be a state in which the conductive deposited film has been removed by wet cleaning the surface of the probe device 70.

[0083] In step S202, the initial state plasma is generated, and the initial state plasma voltage V p初期 The control device 3 measures the initial plasma voltage V via the probe device 70 and the monitor device 80.p初期 The following is measured: The signal generator 82 controls the fundamental wave (first harmonic) of the current measured by the current measuring unit to become a predetermined AC current I. The voltage measured by the voltage measuring unit at that time is the initial plasma voltage V p初期 Let's assume that.

[0084] In the initial state, no conductive deposited film is present on the surface of the probe device 70, and the circuit model is as shown in Figure 6. Therefore, the voltage measured by the voltage measurement unit is used to determine the initial plasma voltage V p初期 The initial plasma voltage V is... p初期 As described above using Figures 7 to 10, it is preferable to detect the parasitic capacity while eliminating its influence.

[0085] In step S203, a conductive deposition film is deposited on the surface of the probe device 70. Here, as shown in Figure 4, the substrate processing (S101) and cleaning process (S102) are repeated. As a result, a conductive deposition film, insulating film, etc., are deposited on the surface of the probe device 70.

[0086] In step S204, an operating plasma is generated, and the operating state measurement voltage V p稼働 The control device 3 controls the microwave output unit 30 and supplies a predetermined microwave from the microwave output unit 30 to the microwave radiation mechanism 50, generating plasma in the processing container 1. The control device 3 also controls the signal transmitter 82 to supply a predetermined alternating current I to the plasma. The control device 3 also measures the operating status voltage V via the probe device 70 and the monitor device 80. p稼働 The following is measured: The signal generator 82 controls the fundamental wave (first harmonic) of the current measured by the current measuring unit to become a predetermined AC current I. The voltage detected by the voltage measuring unit at that time is the operating state measurement voltage V p稼働 Let's assume that.

[0087] The predetermined alternating current I supplied to the plasma in step S204 is the same value as the predetermined alternating current I supplied to the plasma in step S202. That is, by keeping the current flowing through the plasma constant, the fundamental wave voltage V applied to the plasma is constant. p As long as the plasma state does not change, it remains constant, and the distortion component is the second harmonic current I 2,plasma It also remains constant.

[0088] The operating state refers to the state after the initial state, where at least one cleaning process (S102) has been performed and a conductive deposited film has been deposited on the surface of the probe device 70. In the operating state, a conductive deposited film is deposited on the surface of the probe device 70, and the circuit model is as shown in Figure 12. Therefore, the measured voltage V measured by the voltage measurement unit p稼働 The plasma voltage V p and conductive deposited film voltage V r It is the sum of (V p稼働 =V p +V r ).

[0089] In step S205, the conductive deposition film voltage V r The following is derived. Here, the measured voltage V of the operating state measured in step S204 is used. p稼働 From the initial state plasma voltage V measured in step S202 p初期 Subtracting this will result in the conductive deposited film voltage V r Derive (V r =V p稼働 -V p初期 ).

[0090] In step S206, the true plasma voltage V p The following is derived. Here, the measured voltage V in the operating state is p稼働 From conductive deposited film voltage V r By subtracting this, the true plasma voltage V in the operating state is obtained. p Derive (V p =V p稼働 -V r ).

[0091] In step S207, the state of the plasma (plasma electron temperature T e Plasma ion density n i ) is derived. Here, the plasma voltage V derived in step S206 is derived. p Based on a predetermined alternating current I, the plasma state (plasma electron temperature T) is determined. e Plasma ion density n i Derive ).

[0092] As a result, even when a conductive deposited film is deposited on the surface of the probe device 70, the plasma voltage V can be suitably maintained. p This allows us to derive the plasma state (plasma electron temperature T e Plasma ion density n i ) can be derived.

[0093] Furthermore, in the initial state, the plasma voltage V p初期 In the substrate processing performed after the measurement and before the first cleaning process (S102) is executed, assuming that no conductive deposited film has been deposited on the surface of the probe device 70, the plasma voltage V is used with the circuit model shown in Figure 6. p The derived plasma voltage V can be derived. p Based on the above, the state of the plasma (plasma electron temperature T e Plasma ion density n i ) can be derived.

[0094] Then, after the first cleaning process (S102, S203) is performed, the conductive deposited film voltage V is determined by the processes in steps S204 and S205. r The following is derived. Also, the conductive deposited film voltage V r The thickness of the conductive deposited film may be estimated based on this.

[0095] Then, in the substrate processing performed before the second cleaning process (S102) is executed, the circuit model shown in Figure 12 and the derived conductive deposited film voltage V are used. r Using plasma voltage V pThe following can be derived (S206). Also, the derived plasma voltage V p Based on the above, the state of the plasma (plasma electron temperature T e Plasma ion density n i ) can be derived (S207).

[0096] Similarly, each time the cleaning process (S102, S203) is performed, the conductive deposited film voltage V r The following is derived (S204, S205): In the substrate processing performed between this point and the execution of the next cleaning process (S102), the circuit model shown in Figure 12 and the derived conductive deposited film voltage V are used. r Using plasma voltage V p The following can be derived (S206). Also, the derived plasma voltage V p Based on the above, the state of the plasma (plasma electron temperature T e Plasma ion density n i ) can be derived (S207).

[0097] Furthermore, in the initial state of step S202 and the operating state of step S204, the second harmonic current I 2,plasma This can also be determined by the process shown in Figures 9 and 10. Below, the second harmonic current I obtained in the initial state is 2,plasma The second harmonic current I 2,plasma,初期 The second harmonic current I is determined in the operating state. 2,plasma The second harmonic current I 2,plasma,稼働 Let's assume that.

[0098] Here, the second harmonic current I is determined in the operating state (the state in which the conductive deposited film is deposited). 2,plasma,稼働 The following relationships exist:

[0099] The second harmonic current I is determined. 2,plasma,稼働 = Plasma voltage V 2,plasma / ( Plasma voltage V 2,plasma +Conductive deposited film voltage V r ) × True second harmonic current I 2,plasma

[0100] Here, the true second harmonic current I in the operating state 2,plasma This is the second harmonic current I in the initial state. 2,plasma,初期 Since this is equal to the second harmonic current I obtained in the operating state 2,plasma,稼働 The second harmonic current I is determined in the initial state. 2,plasma,初期 By dividing by V, 2,plasma / (V 2,plasma +V r ) can be derived.

[0101] The conductive deposited film voltage V is derived in step S205. r , and / or the second harmonic current I in the initial and operating states 2,plasma Find the period V from 2,plasma / (V 2,plasma +V r By monitoring the following, the state (thickness, etc.) of the conductive deposited film on the surface of the probe device 70 can be monitored. Furthermore, if these values ​​fall outside a predetermined range, it may be determined that wet cleaning should be performed on the surface of the probe device 70.

[0102] Also, conductive deposited film voltage V r The abnormality or normality of the plasma processing apparatus 100 may be determined based on the fluctuation of the conductive deposited film voltage V during substrate processing. r If the plasma voltage V changes more rapidly than the previous value, p It can be estimated that this is also changing rapidly, and it may be determined that there is an abnormality in the plasma processing device 100. Also, during the cleaning process, the conductive deposited film voltage V r If the value changes abruptly compared to the previous value, it may be estimated that the amount of conductive deposited film has changed abnormally, and the plasma processing apparatus 100 may be judged to be malfunctioning. Also, the second harmonic current I 2,plasma or conductive deposited film voltage V r The system may be configured to determine that there is an abnormality in the plasma processing apparatus 100 and stop the next substrate processing if the value deviates by more than, for example, ±10% from a reference value. If an abnormality is determined in the plasma processing apparatus 100, the processing container 1 may be opened and maintenance may be performed.

[0103] Although the plasma processing apparatus 100 has been described above, this disclosure is not limited to the embodiments described above, and various modifications and improvements are possible within the scope of the gist of this disclosure as described in the claims. [Explanation of Symbols]

[0104] 33 Control Unit 70 probe devices 72 Blocking Capacitors 80 Monitoring device 81 Coaxial Cable 82 Signal Transmitter 85 Measurement circuit 100 Plasma Processing Equipment W board U Plasma Generation Space

Claims

1. A plasma measurement method for measuring the state of a plasma using a probe device provided in a plasma processing apparatus and a measurement circuit including a signal generator that outputs a fixed alternating current, The process involves supplying a fixed alternating current to the plasma via the probe device while plasma is generated in the plasma processing apparatus in an initial state where no conductive deposited film is deposited on the surface of the probe device, and measuring the initial state plasma voltage with the measurement circuit. A step of supplying a fixed alternating current to the plasma via the probe device while the plasma is generated in the operating plasma processing apparatus, in which the conductive deposited film is deposited on the surface of the probe device, and measuring the operating voltage with the measurement circuit, A step of subtracting the initial state plasma voltage from the measured voltage to derive the conductive deposited film voltage, The process includes a step of deriving the plasma state using the plasma voltage obtained by subtracting the conductive deposited film voltage from the measured voltage. Plasma measurement method.

2. After the initial state and before the operating state, the process includes a step of dry cleaning the inside of the processing container of the plasma processing apparatus using a fluorine-containing gas. The plasma measurement method according to claim 1.

3. After the dry cleaning step is completed, the steps of measuring the measurement voltage and deriving the conductive deposited film voltage are performed. The plasma measurement method according to claim 2.

4. The thickness of the conductive deposited film is estimated based on the ratio of the second harmonic current in the initial state to the second harmonic current in the operating state. The plasma measurement method according to claim 1.

5. Based on the conductive deposited film voltage, an abnormality in the plasma processing apparatus is determined. The plasma measurement method according to claim 1.

6. A probe device installed in the plasma processing apparatus, A measurement circuit including a signal generator that outputs a fixed AC current, A plasma measurement system comprising a control unit and a plasma state measurement system, The control unit, The process involves supplying a fixed alternating current to the plasma via the probe device while plasma is generated in the plasma processing apparatus in an initial state where no conductive deposited film is deposited on the surface of the probe device, and measuring the initial state plasma voltage with the measurement circuit. A step of supplying a fixed alternating current to the plasma via the probe device while the plasma is generated in the operating plasma processing apparatus, in which the conductive deposited film is deposited on the surface of the probe device, and measuring the operating voltage with the measurement circuit, A step of subtracting the initial state plasma voltage from the measured voltage to derive the conductive deposited film voltage, The system is configured to perform the following steps: deriving the plasma state using the plasma voltage obtained by subtracting the conductive deposited film voltage from the measured voltage. Plasma measurement system.

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