Plasma processing apparatus and etching method
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2026-01-30
- Publication Date
- 2026-08-13
Smart Images
Figure JP2026003314_13082026_PF_FP_ABST
Abstract
Description
Plasma Processing Apparatus and Etching Method
[0001] The present disclosure relates to a plasma processing apparatus and an etching method.
[0002] Patent Document 1 discloses a plasma processing apparatus including a chamber, a first matching circuit coupled to the chamber, a second matching circuit coupled to the chamber, a first RF generation unit coupled to the first matching circuit and configured to generate a first RF pulse signal including a plurality of pulse cycles, a second RF generation unit coupled to the second matching circuit and configured to generate a second RF pulse signal including the plurality of pulse cycles, and a third RF generation unit coupled to the second matching circuit and configured to generate a third RF pulse signal including the plurality of pulse cycles.
[0003] Japanese Patent Application Laid-Open No. 2022-48032
[0004] In one aspect, the present disclosure provides a plasma processing apparatus and an etching method for suppressing the transition of the potential of a substrate to a positive potential.
[0005] To solve the above problems, according to one embodiment, a plasma processing apparatus includes a plasma processing chamber, a substrate support unit disposed in the plasma processing chamber, having a bias electrode, and supporting a substrate, a gas supply unit configured to supply a processing gas into the plasma processing chamber, a first high-frequency power supply configured to supply a source RF signal for plasmaizing the processing gas in the plasma processing chamber, a voltage pulse source configured to supply a negative voltage pulse signal obtained by pulsing a negative DC voltage to the bias electrode, a second high-frequency power supply configured to supply a bias RF signal to the bias electrode, and a control unit. The control unit is configured to supply the processing gas from the gas supply unit into the plasma processing chamber, supply a source RF signal from the first high-frequency power supply to generate plasma of the processing gas in the plasma processing chamber, supply the negative voltage pulse signal to the bias electrode, and supply the bias RF signal to the bias electrode when etching the substrate.
[0006] In one aspect, it is possible to provide a plasma processing apparatus and etching method that suppress the transition of the substrate's potential to a positive potential.
[0007] An example of a diagram illustrating the configuration of a plasma processing system. An example of a diagram illustrating the configuration of an inductively coupled plasma processing apparatus. An example of a diagram illustrating the circuit connected to the bias electrode of the base. An example of a flowchart illustrating an example of a substrate processing method. An example of a graph illustrating the relationship between power supply voltage and substrate voltage. An example of a graph illustrating the relationship between power supply voltage and substrate voltage. An example of a graph illustrating the relationship between power supply voltage and substrate voltage. An example of a graph illustrating the relationship between power supply voltage and substrate voltage. A graph showing an example of substrate voltage. A graph showing an example of substrate voltage. A graph showing an example of substrate voltage. A graph showing an example of substrate voltage. A graph showing an example of substrate voltage. A graph showing an example of substrate voltage. A graph showing an example of substrate voltage. A graph showing an example of substrate voltage. A graph showing an example of substrate voltage. A graph showing an example of substrate voltage.
[0008] Various exemplary embodiments will be described in detail below with reference to the drawings. In each drawing, the same or corresponding parts will be denoted by the same reference numerals.
[0009] [Plasma Processing System] Figure 1 is an example of a diagram illustrating an example of the configuration of a plasma processing system. In one embodiment, the plasma processing system includes a plasma processing apparatus 1 and a control unit 2. The plasma processing system is an example of a substrate processing system, and the plasma processing apparatus 1 is an example of a substrate processing apparatus. The plasma processing apparatus 1 includes a plasma processing chamber 10, a substrate support unit 11, and a plasma generation unit 12. The plasma processing chamber 10 has a plasma processing space. The plasma processing chamber 10 also has at least one gas supply port for supplying at least one processing gas to the plasma processing space, and at least one gas outlet for discharging gas from the plasma processing space. The gas supply port is connected to a gas supply unit 20, which will be described later, and the gas outlet is connected to an exhaust system 40, which will be described later. The substrate support unit 11 is located in the plasma processing space and has a substrate support surface for supporting a substrate.
[0010] The plasma generation unit 12 is configured to generate plasma from at least one processing gas supplied into the plasma processing space. The plasma formed in the plasma processing space may be capacitively coupled plasma (CCP), inductively coupled plasma (ICP), ECR (Electron Cyclotron Resonance) plasma, helicon wave excited plasma (HWP), or surface wave plasma (SWP), etc. Various types of plasma generation units, including AC (Alternating Current) plasma generation units and DC (Direct Current) plasma generation units, may also be used. In one embodiment, the AC signal (AC power) used in the AC plasma generation unit has a frequency in the range of 100 kHz to 10 GHz. Therefore, the AC signal includes an RF (Radio Frequency) signal and a microwave signal. In one embodiment, the RF signal has a frequency in the range of 100 kHz to 150 MHz.
[0011] The control unit 2 processes computer-executable instructions that cause the plasma processing apparatus 1 to perform the various processes described herein. The control unit 2 may be configured to control the elements of the plasma processing apparatus 1 to perform the various processes described herein. In one embodiment, part or all of the control unit 2 may be included in the plasma processing apparatus 1. The control unit 2 is implemented, for example, by a computer 2a. The control unit 2 may include a processing unit 2a1, a storage unit 2a2, and a communication interface 2a3. The functions realized by the processing unit 2a1 described herein may be implemented in a circuit or processing circuit, including a general-purpose processor, an application-specific processor, integrated circuits, ASICs (Application Specific Integrated Circuits), a CPU (Central Processing Unit), a conventional circuit, and / or a combination thereof, programmed to realize the described functions. The processor is considered to be a circuit or processing circuit, including transistors and other circuits. The processor may be a programmed processor that executes a program stored in the storage unit 2a2. This program may be pre-stored in the storage unit 2a2 or retrieved via a medium when needed. The acquired program is stored in the storage unit 2a2 and read from the storage unit 2a2 and executed by the processing unit 2a1. The medium may be various storage media readable by the computer 2a, or it may be a communication line connected to the communication interface 2a3. The storage unit 2a2 may include RAM (Random Access Memory), ROM (Read Only Memory), HDD (Hard Disk Drive), SSD (Solid State Drive), or a combination thereof. The communication interface 2a3 may communicate with the plasma processing device 1 via a communication line such as a LAN (Local Area Network).In this disclosure, circuits, units, and means are hardware programmed to perform or configured to perform the functions described. Such hardware may be any hardware described in this disclosure, or any hardware known to be programmed to perform or execute the functions described. If such hardware is a processor that is considered to be a type of circuit, such circuit, means, or unit is a combination of hardware and software used to constitute such hardware and / or processor.
[0012] The following describes an example configuration of an inductively coupled plasma processing apparatus as an example of a plasma processing apparatus 1. Figure 2 is an example of a diagram illustrating an example configuration of an inductively coupled plasma processing apparatus.
[0013] The inductively coupled plasma processing apparatus 1 includes a plasma processing chamber 10, a gas supply unit 20, a power supply system 30, and an exhaust system 40. The plasma processing chamber 10 includes a dielectric window 101. The plasma processing apparatus 1 also includes a substrate support unit 11, a gas introduction unit, and an antenna 14. The substrate support unit 11 is located inside the plasma processing chamber 10. The antenna 14 is located on or above the plasma processing chamber 10 (i.e., on or above the dielectric window 101). The plasma processing chamber 10 has a plasma processing space 10s defined by the dielectric window 101, the side walls 102 of the plasma processing chamber 10, and the substrate support unit 11. The plasma processing chamber 10 is grounded.
[0014] The substrate support portion 11 includes a main body portion 111 and a ring assembly 112. The main body portion 111 has a central region 111a for supporting the substrate W and an annular region 111b for supporting the ring assembly 112. A wafer is an example of a substrate W. The annular region 111b of the main body portion 111 surrounds the central region 111a of the main body portion 111 in a plan view. The substrate W is placed on the central region 111a of the main body portion 111, and the ring assembly 112 is placed on the annular region 111b of the main body portion 111 so as to surround the substrate W on the central region 111a of the main body portion 111. Therefore, the central region 111a is also called the substrate support surface for supporting the substrate W, and the annular region 111b is also called the ring support surface for supporting the ring assembly 112.
[0015] In one embodiment, the main body 111 includes a base 1110 and an electrostatic chuck 1111. The base 1110 includes a conductive member. The conductive member of the base 1110 can function as a bias electrode. The electrostatic chuck 1111 is placed on the base 1110. The electrostatic chuck 1111 includes a ceramic member 1111a and an electrostatic chuck electrode 1111b placed within the ceramic member 1111a. The electrostatic chuck electrode 1111b is also called a clamping electrode. In one embodiment, the electrostatic chuck electrode 1111b is electrically connected or coupled to a chuck power supply. The chuck power supply may be a DC power supply or an AC power supply. The ceramic member 1111a has a central region 111a. In one embodiment, the ceramic member 1111a also has an annular region 111b. Furthermore, other members surrounding the electrostatic chuck 1111, such as an annular electrostatic chuck or an annular insulating member, may have an annular region 111b. In this case, the ring assembly 112 may be placed on the annular electrostatic chuck or the annular insulating member, or on both the electrostatic chuck 1111 and the annular insulating member. Also, at least one bias electrode, electrically connected or coupled to the power supply 31 and / or power supply 32 described later, may be placed inside the ceramic member 1111a. Furthermore, the conductive member of the base 1110 and the bias electrode inside the ceramic member 1111a may function as multiple bias electrodes. Also, the electrostatic chuck electrode 1111b may function as a bias electrode. Therefore, the substrate support portion 11 includes at least one bias electrode.
[0016] The ring assembly 112 includes one or more annular members. In one embodiment, the one or more annular members include one or more edge rings and at least one covering ring. The edge rings are formed of a conductive or insulating material, and the covering rings are formed of an insulating material.
[0017] The substrate support section 11 may also include a temperature control module configured to adjust at least one of the electrostatic chuck 1111, the ring assembly 112, and the substrate to a target temperature. The temperature control module may include a heater, a heat transfer medium, a flow path 1110a, or a combination thereof. A heat transfer fluid such as brine or gas flows through the flow path 1110a. In one embodiment, the flow path 1110a is formed within the base 1110, and one or more heaters are arranged within the ceramic member 1111a of the electrostatic chuck 1111. The substrate support section 11 may also include a heat transfer gas supply section configured to supply heat transfer gas to the gap between the back surface of the substrate W and the central region 111a.
[0018] The gas introduction section is configured to introduce at least one processing gas from the gas supply section 20 into the plasma processing space 10s. In one embodiment, the gas introduction section includes a central gas injector (CGI) 13. The central gas injector 13 is located above the substrate support section 11 and is attached to a central opening formed in the dielectric window 101. The central gas injector 13 has at least one gas supply port 13a, at least one gas flow path 13b, and at least one gas inlet 13c. The processing 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 13c. In addition to or instead of the central gas injector 13, the gas introduction section may also include one or more side gas injectors (SGIs) attached to one or more openings formed in the side wall 102.
[0019] The gas supply unit 20 may include at least one gas source 21 and at least one flow controller 22. In one embodiment, the gas supply unit 20 is configured to supply at least one processing gas to the gas inlet from a corresponding gas source 21 via a corresponding flow controller 22. Each flow controller 22 may include, for example, a mass flow controller or a pressure-controlled flow controller. Furthermore, the gas supply unit 20 may include at least one flow modulation device that modulates or pulses the flow rate of at least one processing gas.
[0020] The power supply system 30 includes a power supply 31 that is electrically connected to or coupled to the plasma processing chamber 10. In one embodiment, the power supply 31 is electrically connected to or coupled to the plasma processing chamber 10 via at least one impedance matcher. The impedance matcher may be a mechanically controlled matcher or an electronically controlled matcher. The power supply 31 is configured to supply at least one RF signal (RF power) to at least one bias electrode and antenna 14. This generates plasma from at least one processing gas supplied to the plasma processing space 10s. Therefore, the power supply 31 can function as at least part of the plasma generation unit 12. Furthermore, by supplying a bias RF signal to at least one bias electrode, a bias potential is generated on the substrate W, and ions in the formed plasma can be drawn into the substrate W.
[0021] The power supply 31 includes a first RF generation unit 31a and a second RF generation unit 31b. The first RF generation unit 31a is electrically connected to or coupled to the antenna 14 and is configured to generate a source RF signal (source RF power, first high-frequency power) to generate plasma in the plasma processing space 10s. In one embodiment, the first RF generation unit 31a is electrically connected to or coupled to the antenna 14 via at least one impedance matcher. In one embodiment, the source RF signal has a frequency in the range of 10 MHz to 150 MHz. In one embodiment, the first RF generation unit 31a may be configured to generate a plurality of source RF signals having different frequencies. The generated one or more source RF signals are supplied to the antenna 14.
[0022] The second RF generation unit 31b is electrically connected to or coupled to at least one bias electrode and is configured to generate a bias RF signal (bias RF power, second high-frequency power). In one embodiment, the second RF generation unit 31b is electrically connected to or coupled to at least one bias electrode via at least one impedance matcher 36 (see Figure 3). 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 lower frequency than the frequency of the source RF signal. In one embodiment, the bias RF signal has a frequency in the range of 100 kHz to 60 MHz. In one embodiment, the second RF generation unit 31b may be configured to generate a plurality of bias RF signals having different frequencies. The generated one or more bias RF signals are supplied to at least one bias electrode. In various embodiments, at least one of the source RF signal and the bias RF signal may be pulsed.
[0023] The power supply system 30 may also include a power supply 32 that is electrically connected to or coupled to the plasma processing chamber 10. The power supply 32 includes a voltage generation unit 32a. In one embodiment, the voltage generation unit 32a is electrically connected to or coupled to at least one bias electrode and is configured to generate a voltage signal. The generated voltage signal is applied to at least one bias electrode.
[0024] In various embodiments, the voltage signal may be pulsed. In this case, the voltage generation unit 32a functions as a voltage pulse generation unit (see Figure 3, described later) configured to generate a sequence of voltage pulses. Thus, a sequence of voltage pulses is applied to at least one bias electrode. In one embodiment, the sequence of voltage pulses has multiple cycles, each cycle including a burst of voltage pulses in a first period and a constant reference voltage in a second period. That is, in the sequence of voltage pulses, bursts of voltage pulses are repeated. The absolute value of the voltage level of the voltage pulse is greater than the absolute value of the voltage level of the reference voltage. The voltage pulse may have an arbitrary waveform, such as a rectangle, trapezoid, triangle, or a combination thereof, and the arbitrary waveform may change over time. The voltage pulse 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 voltage generation unit 32a may be provided in addition to the power supply 31, or it may be provided in place of the second RF generation unit 31b.
[0025] 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 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 generation unit may be connected to both the outer coil and the inner coil, or separate RF generation units may be connected to the outer coil and the inner coil separately.
[0026] The exhaust system 40 may be connected to, for example, a gas outlet 10e located at the bottom of the plasma processing chamber 10. The exhaust system 40 may include a pressure regulating valve and a vacuum pump. The pressure regulating valve regulates the pressure in the plasma processing space 10s. The vacuum pump may include a turbomolecular pump, a dry pump, or a combination thereof.
[0027] Next, the configuration for supplying a bias signal (bias voltage) to the bias electrode of the base 1110 will be explained using Figure 3. Figure 3 is an example of a diagram illustrating the circuit connected to the bias electrode of the base 1110.
[0028] The second RF generation unit 31b is electrically connected to or coupled to the bias electrode via an impedance matching unit 36. The second RF generation unit 31b generates a bias RF signal (bias RF power, second high-frequency power). The bias RF signal has a frequency of, for example, 13 MHz. The frequency of the bias RF signal is preferably in the range of 1 to 100 MHz, and more preferably in the range of 2 to 60 MHz.
[0029] The impedance matching unit 36 adjusts (matches) the impedance between the power supply side (second RF generation unit 31b) and the load side (plasma).
[0030] The voltage generation unit 32a is electrically connected to or coupled to the bias electrode via the high-frequency filter 37. The voltage generation unit 32a generates a negative voltage pulse signal.
[0031] In the example shown in Figure 3, the voltage generation unit 32a includes a DC power supply 32b, a lamp voltage power supply 32c, and a pulse generation unit 32d. The voltage generation unit 32a may also include at least one of the DC power supply 32b and the lamp voltage power supply 32c.
[0032] The DC power supply 32b generates a negative DC voltage. For example, the voltage generation unit 32a generates a negative voltage V1.
[0033] The lamp voltage power supply 32c generates a negative lamp voltage. For example, the lamp voltage power supply 32c generates a negative lamp voltage (a voltage that changes monotonically from voltage V1 to voltage V2 over time).
[0034] The pulse generation unit 32d is supplied with a negative DC voltage from the DC power supply 32b. The pulse generation unit 32d periodically switches the supplied negative DC voltage on and off to create pulses, and supplies the generated voltage pulses (see Figure 5A, described later) to the bias electrode via the high-frequency filter 37.
[0035] Furthermore, the pulse generation unit 32d is supplied with a negative lamp voltage from the lamp voltage power supply 32c. The pulse generation unit 32d periodically turns the supplied negative lamp voltage on and off to create pulses, and supplies the generated voltage pulses (see Figure 5C, described later) to the bias electrode via the high-frequency filter 37.
[0036] The high-frequency filter 37 is a bandstop filter that sufficiently attenuates the frequency band including the bias RF signal (e.g., 13 MHz) generated by the second RF generation unit 31b. Furthermore, it is preferable that the high-frequency filter 37 is a bandstop filter with a high Q value. That is, it is preferable that the high-frequency filter 37 is a filter that selectively stops the bias RF signal generated by the second RF generation unit 31b.
[0037] [Substrate Processing] Next, an example of a substrate processing method in which a desired substrate processing (etching process) is performed on the substrate W using the plasma processing apparatus 1 will be explained with reference to Figure 4. Figure 4 is an example of a flowchart illustrating an example of a substrate processing method.
[0038] In step S101, the substrate W is prepared. Here, the substrate W is transported into the plasma processing chamber 10 by a transport device (not shown), and the substrate W is supported (placed) on the substrate support section 11. The substrate W has a film to be etched and a mask having a pattern of openings formed on the film to be etched. The film to be etched is, for example, a silicon oxide film, a silicon nitride film, an organic film, a metal film (titanium, aluminum, zirconium, hafnium, ruthenium), etc. The mask is, for example, a silicon oxide film, an organic film, a metal film (titanium, aluminum, zirconium, hafnium, ruthenium), etc.
[0039] In step S102, a source RF signal is supplied to generate plasma. Here, the control unit 2 controls the gas supply unit 20 to supply processing gas into the plasma processing chamber 10. The control unit 2 also controls the first RF generation unit 31a to supply a source RF signal (source RF power, first high-frequency power) to the antenna 14 for generating plasma. This generates plasma of the processing gas in the plasma processing space 10s. Here, the plasma of the processing gas generates positive ions. The source RF signal is, for example, 27 MHz. The processing gas is, for example, O ２ These include halogen-containing gases (fluorocarbon gas, hydrogen fluoride gas, tungsten fluoride gas, hydrogen bromide gas, etc.).
[0040] Furthermore, plasma generation continues throughout the subsequent processing until the substrate processing is completed (S105, YES).
[0041] In step S103, a first-level negative voltage pulse signal is supplied. Here, the control unit 2 controls the voltage generation unit 32a to supply a first-level (high) negative voltage pulse to the bias electrode. In other words, the control unit 2 controls the pulse generation unit 32d to turn on the voltage supply. The absolute value of the first-level (high) voltage is greater than the absolute value of the second-level (low) voltage. The first-level (high) negative voltage pulse may be constant (see Figure 5A described later) or it may change (see Figure 5C described later).
[0042] By supplying a negative voltage pulse to the bias electrode, positive ions are drawn from the plasma into the substrate W, forming recesses perpendicular to the substrate W.
[0043] In step S104, a negative voltage pulse signal of the second level is supplied while superposing a bias RF signal. Here, the control unit 2 controls the voltage generation unit 32a to supply a negative voltage pulse of the second level (low) to the bias electrode. In other words, the control unit 2 controls the pulse generation unit 32d to turn off the voltage supply. Further, the control unit 2 controls the second RF generation unit 31b to supply second high-frequency power (bias RF signal, bias RF power) to the bias electrode. Thereby, the power supply system 30 superposes the second high-frequency power on the negative voltage pulse of the second level (low) and supplies it to the bias electrode.
[0044] In step S105, it is determined whether or not a predetermined repetition has ended. If the predetermined repetition has not ended (S105·NO), the process of the control unit 2 returns to step S103, and steps S103 to S104 are repeated. If the predetermined repetition has ended (S105·YES), the substrate processing is terminated.
[0045] Here, a negative voltage pulse signal is used as the bias signal supplied to the bias electrode for drawing ions into the substrate W. Thereby, the spread of the ion energy distribution is small, and the perpendicularity of the ions incident on the substrate W can be improved. Further, a concave portion having a shape perpendicular to the substrate W can be formed by the etching process. Further, roughness or the like on the side wall of the concave portion can be suppressed.
[0046] Next, the relationship between the power supply voltage supplied by the power supply to the bias electrode and the potential (substrate voltage) of the substrate surface will be described using FIGS. 5A to 6B.
[0047] FIGS. 5A to 5D are an example of graphs for explaining the power supply voltage and the substrate voltage. In FIGS. 5A to 5D, the horizontal axis represents time, and the vertical axis represents voltage (power supply voltage, substrate voltage).
[0048] Figure 5A is a graph showing an example of the power supply voltage supplied to the bias electrode by the power supply system 30. Here, the negative voltage pulse at the first level (high) is constant at voltage V1. The negative voltage pulse at the second level (low) is constant at voltage 0 [V]. A voltage pulse signal repeating between the first level (high) and the second level (low) is supplied to the bias electrode.
[0049] Figure 5B is a graph showing an example of the substrate voltage when the voltage pulse signal shown in Figure 5A is supplied. As can be seen by comparing Figures 5A and 5B, the voltage waveforms of the power supply voltage and the substrate voltage are different. Specifically, when a first-level (high) negative voltage pulse signal is supplied, the absolute value of the substrate voltage decreases over time.
[0050] Figure 5C is a graph showing another example of the power supply voltage supplied to the bias electrode by the power supply system 30. Here, the first level (high) negative voltage pulse changes from voltage V1 to voltage V2. Here, the absolute value of voltage V2 is greater than the absolute value of voltage V1.
[0051] Figure 5D is a graph showing an example of substrate voltage when the voltage pulse signal shown in Figure 5C is supplied. Here, as shown in Figure 5C, when supplying a first-level (high) negative voltage pulse signal, the absolute value of the voltage is increased over time (voltage V1 → voltage V2). This makes it possible to suppress changes in substrate voltage, as shown in comparison with Figure 5B.
[0052] Next, the change in substrate voltage when switching a negative voltage pulse from the first level (high) to the second level (low) will be further explained using Figures 6A to 6B. Figures 6A to 6B are graphs showing an example of substrate voltage. In Figures 6A to 6B, the horizontal axis represents time and the vertical axis represents substrate voltage.
[0053] Figure 6A is a graph showing an example of substrate voltage when the voltage pulse signal shown in Figure 5C is supplied.
[0054] When the negative voltage pulse is switched from the first level (high) to the second level (low), the substrate voltage transitions to a positive potential. That is, during the period when the negative voltage pulse signal is off (second level), there is a period when the substrate surface is at a positive potential. Here, negatively charged particle sources, which are by-products of the plasma treatment, are floating in the plasma. When the substrate voltage is at a positive potential, there is a risk that the negatively charged particle sources will be attracted to the surface of the substrate W. And there is a risk that the etching process will be inhibited by the particle sources attracted to the substrate surface.
[0055] In contrast, as shown in step S104, when supplying a second-level negative voltage pulse signal to the bias electrode, a bias RF signal is superimposed and supplied. That is, the bias RF signal is supplied in synchronization with the period when the negative voltage pulse signal is off (second level). Alternatively, the bias RF signal is supplied in synchronization with the period when the substrate surface is at a positive potential. Figure 6B is a graph showing an example of substrate voltage in the substrate processing shown in Figure 4.
[0056] As shown in Figures 6A to 6B, the bias signal obtained by superimposing the bias RF signal on the second-level negative voltage pulse signal preferably has a moving average (shown by a dashed line) of 0 [V] or a negative potential. Here, the pulse generation unit 32d is controlled to turn off the DC voltage supply. In addition, by supplying the bias RF signal to the bias electrode, a negative self-bias voltage is applied to the bias electrode. As a result, the moving average of the bias signal becomes 0 [V] or a negative potential.
[0057] Furthermore, it is preferable that the bias RF signal be in a frequency range that positively charged or negatively charged particle sources cannot follow (1 to 100 MHz, preferably 2 to 60 MHz, for example 13 MHz). This makes it possible to suppress the adhesion of particle sources to the surface of the substrate.
[0058] Figures 7A to 9C are graphs showing examples of substrate voltage. In Figures 7A to 9C, the horizontal axis represents time, and the vertical axis represents substrate voltage.
[0059] Figure 7A shows an example where the process of supplying a first-level negative voltage pulse signal without superimposing a bias RF signal (DC-on) and the process of supplying a second-level negative voltage pulse signal without superimposing a bias RF signal (DC-off) are repeated. As shown in Figure 7A, the substrate voltage transitions to a positive potential during the DC-off period.
[0060] Figure 7B shows an example where the process of supplying a first-level negative voltage pulse signal without superimposing a bias RF signal, and the process of supplying a second-level negative voltage pulse signal with a bias RF signal superimposed, are repeated. The moving average of the substrate voltage is shown by a white dashed line. As shown in Figure 7B, the moving average of the substrate voltage can be kept below 0 [V] (see arrow 702).
[0061] Figure 7C shows an example where the process of supplying a first-level negative voltage pulse signal superimposed with a bias RF signal and the process of supplying a second-level negative voltage pulse signal superimposed with a bias RF signal are repeated. The moving average of the substrate voltage is shown by a white dashed line. As shown in Figure 7C, the moving average of the substrate voltage can be kept below 0 [V] (see arrow).
[0062] Figure 8A shows an example similar to Figure 7A, where the process of supplying a first-level negative voltage pulse signal without superimposing a bias RF signal (DC-on) and the process of supplying a second-level negative voltage pulse signal without superimposing a bias RF signal (DC-off) are repeated. In this case, the substrate voltage exceeds 0 [V].
[0063] Figure 8B shows the case where the negative voltage pulse is switched from the first level to the second level, and the superposition of the bias RF signal is started at the same time. In this case, the moving average of the substrate voltage can be kept below 0 [V].
[0064] Figure 8C shows the case where the negative voltage pulse is switched from the first level to the second level, and then the superposition of the bias RF signal begins after a delay time (Duty 8%) has elapsed. In this case, the moving average of the substrate voltage is greater than 0 [V].
[0065] Figure 8D shows the case where the negative voltage pulse is switched from the first level to the second level, and then the superposition of the bias RF signal begins after a delay time (Duty 18%) has elapsed. In this case, the moving average of the substrate voltage is greater than 0 [V].
[0066] As shown in Figures 8A to 8D, it is preferable that the bias RF signal is superimposed at the timing when the negative voltage pulse is switched from the first level to the second level.
[0067] Figure 9A shows an example where the process of supplying a first-level negative voltage pulse signal without superimposing a bias RF signal and the process of supplying a second-level negative voltage pulse signal without superimposing a bias RF signal are repeated. Range 901 is the initial stage of the repetition.
[0068] Figure 9B is an enlarged view of range 901. In the initial stages of voltage pulse repetition, the substrate voltage increases above 0 [V] (see arrow 902).
[0069] Figure 9C is an enlarged view corresponding to range 901 in an embodiment where the process of supplying a first-level negative voltage pulse signal superimposed with a bias RF signal and the process of supplying a second-level negative voltage pulse signal superimposed with a bias RF signal are repeated. The moving average is shown by line 903. In this way, even in the initial stages when the voltage pulse repetition starts, the moving average of the substrate voltage can be kept below 0 [V].
[0070] It should be noted that the present invention is not limited to the configurations shown in the above embodiments, including combinations with other elements. These aspects can be modified without departing from the spirit of the present invention and can be appropriately determined according to their application.
[0071] The embodiments disclosed above include, for example, the following aspects: (Note 1) A plasma processing apparatus comprising: a plasma processing chamber; a substrate support portion disposed within the plasma processing chamber and having a bias electrode for supporting a substrate; a gas supply portion for supplying a processing gas into the plasma processing chamber; a first high-frequency power supply for supplying a source RF signal for plasmaizing the processing gas in the plasma processing chamber; a voltage pulse source for supplying a negative voltage pulse signal obtained by pulsed negative DC voltage to the bias electrode; a second high-frequency power supply for supplying a bias RF signal to the bias electrode; and a control portion, wherein the control portion is configured to, when etching the substrate, supply the processing gas from the gas supply portion into the plasma processing chamber, supply a source RF signal from the first high-frequency power supply to generate plasma of the processing gas in the plasma processing chamber, supply the negative voltage pulse signal to the bias electrode, and supply the bias RF signal to the bias electrode. (Note 2) The plasma processing apparatus according to Note 1, wherein the voltage pulse source supplies the negative voltage pulse signal by periodically turning a negative DC voltage on and off. (Note 3) The plasma processing apparatus according to Note 2, wherein the second high-frequency power supply does not supply the bias RF signal during the period when the negative voltage pulse signal is ON, and supplies the bias RF signal in synchronization with the period when the negative voltage pulse signal is OFF. (Note 4) The plasma processing apparatus according to Note 2, wherein the substrate surface is at a positive potential during the period when the negative voltage pulse signal is OFF, and the second high-frequency power supply supplies the bias RF signal in synchronization with the period when the substrate surface is at a positive potential. (Note 5) The plasma processing apparatus according to Note 2, wherein the second high-frequency power supply supplies the bias RF signal during the period when the negative voltage pulse signal is ON and the period when it is OFF. (Note 6) The plasma processing apparatus according to any one of Notes 2 to 5, wherein the voltage pulse source supplies a constant negative voltage pulse signal during the period when the negative voltage pulse signal is ON.(Note 7) The plasma processing apparatus according to any one of Notes 2 to 5, wherein the voltage pulse source supplies a negative voltage pulse signal whose absolute value increases during the period when the negative voltage pulse signal is ON. (Note 8) The plasma processing apparatus according to any one of Notes 1 to 7, further comprising a high-frequency filter between the bias electrode and the voltage pulse source. (Note 9) An etching method for a plasma processing apparatus comprising: a plasma processing chamber; a substrate support portion disposed within the plasma processing chamber and having a bias electrode and supporting a substrate; a gas supply portion for supplying a processing gas into the plasma processing chamber; a first high-frequency power supply for supplying a source RF signal for plasmaizing the processing gas in the plasma processing chamber; a voltage pulse source for supplying a negative voltage pulse signal obtained by pulsed negative DC voltage to the bias electrode; and a second high-frequency power supply for supplying a bias RF signal to the bias electrode, the etching method comprising: a step of supplying the processing gas from the gas supply portion into the plasma processing chamber; a step of supplying a source RF signal from the first high-frequency power supply to generate plasma of the processing gas in the plasma processing chamber; a step of supplying the negative voltage pulse signal to the bias electrode; and a step of supplying the bias RF signal to the bias electrode.
[0072] Furthermore, this application claims priority based on Japanese Patent Application No. 2025-020273, filed on 10 February 2025, and the entire contents of these Japanese Patent Applications are incorporated herein by reference.
[0073] 1 Plasma processing apparatus 2 Control unit 10 Plasma processing chamber 10s Plasma processing space 11 Substrate support unit 1110 Base (bias electrode) 12 Plasma generation unit 20 Gas supply unit 30 Power supply system 31 Power supply 31a First RF generation unit (first high-frequency power supply) 31b Second RF generation unit (second high-frequency power supply) 32 Power supply 32a Voltage generation unit (voltage pulse source) 32b DC power supply 32c Lamp voltage power supply 32d Pulse generation unit 36 Impedance matching unit 37 Filter 40 Exhaust system W Substrate
Claims
1. A plasma processing apparatus comprising: a plasma processing chamber; a substrate support unit disposed within the plasma processing chamber and having a bias electrode for supporting a substrate; a gas supply unit for supplying a processing gas into the plasma processing chamber; a first high-frequency power supply for supplying a source RF signal for plasmaizing the processing gas in the plasma processing chamber; a voltage pulse source for supplying a negative voltage pulse signal obtained by pulsed negative DC voltage to the bias electrode; a second high-frequency power supply for supplying a bias RF signal to the bias electrode; and a control unit, wherein the control unit is configured to, when etching the substrate, supply the processing gas from the gas supply unit into the plasma processing chamber, supply a source RF signal from the first high-frequency power supply to generate plasma from the processing gas in the plasma processing chamber, supply the negative voltage pulse signal to the bias electrode, and supply the bias RF signal to the bias electrode.
2. The plasma processing apparatus according to claim 1, wherein the voltage pulse source supplies a negative voltage pulse signal by periodically switching a negative DC voltage on and off.
3. The plasma processing apparatus according to claim 2, wherein the second high-frequency power supply does not supply the bias RF signal during the period when the negative voltage pulse signal is ON, and supplies the bias RF signal in synchronization with the period when the negative voltage pulse signal is OFF.
4. The plasma processing apparatus according to claim 2, wherein the substrate surface is at a positive potential during the period when the negative voltage pulse signal is off, and the second high-frequency power supply supplies the bias RF signal in synchronization with the period when the substrate surface is at a positive potential.
5. The plasma processing apparatus according to claim 2, wherein the second high-frequency power supply supplies the bias RF signal during periods when the negative voltage pulse signal is ON and OFF.
6. The plasma processing apparatus according to claim 2, wherein the voltage pulse source supplies a constant negative voltage pulse signal during the period when the negative voltage pulse signal is ON.
7. The plasma processing apparatus according to claim 2, wherein the voltage pulse source supplies a negative voltage pulse signal whose absolute value increases during the period when the negative voltage pulse signal is ON.
8. The plasma processing apparatus according to claim 1, further comprising a high-frequency filter between the bias electrode and the voltage pulse source.
9. An etching method for a plasma processing apparatus comprising: a plasma processing chamber; a substrate support portion disposed within the plasma processing chamber and having a bias electrode for supporting a substrate; a gas supply portion for supplying a processing gas into the plasma processing chamber; a first high-frequency power supply for supplying a source RF signal for plasmaizing the processing gas in the plasma processing chamber; a voltage pulse source for supplying a negative voltage pulse signal obtained by pulsed negative DC voltage to the bias electrode; and a second high-frequency power supply for supplying a bias RF signal to the bias electrode, the etching method comprising: a step of supplying the processing gas from the gas supply portion into the plasma processing chamber; a step of supplying a source RF signal from the first high-frequency power supply to generate plasma of the processing gas in the plasma processing chamber; a step of supplying the negative voltage pulse signal to the bias electrode; and a step of supplying the bias RF signal to the bias electrode.