Substrate processing apparatus and control method for a substrate processing apparatus

Abstract

The present invention provides a substrate processing apparatus and a control method of a substrate processing apparatus, in which a timing at which high-frequency electric power for generating plasma is supplied to plasma at a high power is adjusted with respect to attracted high-frequency electric power in a plasma processing apparatus. The substrate processing apparatus includes: a substrate stage on which a substrate is placed; a first high-frequency power source that supplies a first high-frequency electric power of a first frequency to the substrate stage; an impedance converter that converts an impedance on a load side, as viewed from the first high-frequency power source, to a set impedance that is set; a second high-frequency power source that supplies a second high-frequency electric power of a second frequency that is lower than the first frequency to the substrate stage; and a control section that controls the set impedance of the impedance converter, the control section setting the set impedance in accordance with substrate processing.

Description

Technical Field

[0001] This invention relates to a substrate processing apparatus and a method for controlling the substrate processing apparatus. Background Technology

[0002] For example, Patent Document 1 discloses a plasma etching apparatus that can stably control the load power in a high-frequency power supply.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2015-090770 Summary of the Invention

[0006] The technical problem that the invention aims to solve

[0007] There is a demand for a technology in plasma processing devices that allows for the timing of supplying high-frequency electrical power for plasma generation to the plasma relative to the high-frequency electrical power used for attraction.

[0008] Technical solutions for solving technical problems

[0009] According to one aspect of the present invention, a substrate processing apparatus is provided, comprising: a substrate mounting stage on which a substrate is mounted; a first high-frequency power supply that supplies a first high-frequency electrical power of a first frequency to the substrate mounting stage; an impedance converter that converts an impedance on the load side observed from the first high-frequency power supply into a set impedance; a second high-frequency power supply that supplies a second high-frequency electrical power of a second frequency lower than the first frequency to the substrate mounting stage; and a control unit that controls the set impedance of the impedance converter, wherein the control unit sets the set impedance according to substrate processing.

[0010] Invention Effects

[0011] The present invention provides a technique in a plasma processing apparatus that allows for adjusting the timing of supplying high-frequency electrical power for plasma generation to the plasma at high power relative to the high-frequency electrical power used for attraction.

[0012] Explanation of reference numerals in the attached figures

[0013] 1. Substrate processing device

[0014] 10 mounting platforms

[0015] 21a First High Frequency Power Supply

[0016] 21b Second High Frequency Power Supply

[0017] 22a Impedance Transformer

[0018] 43 Control Department

[0019] W substrate. Attached Figure Description

[0020] Figure 1 This is a cross-sectional view showing the schematic structure of the substrate processing apparatus of this embodiment.

[0021] Figure 2 This is a block diagram showing the structure of the high-frequency power supply and impedance converter for plasma generation in the substrate processing apparatus of this embodiment.

[0022] Figure 3 This is a block diagram showing the structure of the high-frequency power supply and matching device for ion attraction in the substrate processing apparatus of this embodiment.

[0023] Figure 4 This is a flowchart illustrating the processing of the control unit of the substrate processing apparatus in this embodiment.

[0024] Figure 5 This is a diagram illustrating the waveform when high-frequency electrical power is supplied in the substrate processing apparatus of this embodiment.

[0025] Figure 6 This is a diagram illustrating the effect of impedance on waveform when high-frequency electrical power is supplied in the substrate processing apparatus of this embodiment.

[0026] Figure 7 This is a diagram showing the waveform when high-frequency electrical power is supplied under a specified impedance in the substrate processing apparatus of this embodiment.

[0027] Figure 8 This is a graph showing the relationship between impedance and waveform when high-frequency electrical power is supplied in the substrate processing apparatus of this embodiment.

[0028] Figure 9 This is a graph showing the relationship between impedance and electron density of plasma when high-frequency electrical power is supplied in the substrate processing apparatus of this embodiment.

[0029] Figure 10 This is a graph showing the relationship between impedance and etching rate when high-frequency electrical power is supplied in the substrate processing apparatus of this embodiment. Detailed Implementation

[0030] Hereinafter, with reference to the accompanying drawings, a method for carrying out the present invention will be described. In this specification and the accompanying drawings, substantially identical structures are labeled with the same reference numerals to omit redundant descriptions.

[0031] <Overall Structure of Substrate Processing Device 1>

[0032] First, refer to Figure 1An example of the overall structure of the substrate processing device 1 will be described. Figure 1 This is a cross-sectional view showing the schematic structure of the substrate processing apparatus 1 in this embodiment. This embodiment describes an example where the substrate processing apparatus 1 is a RIE (Reactive Ion Etching) type substrate processing apparatus.

[0033] exist Figure 1 In this embodiment, the substrate processing apparatus 1 has a grounded cylindrical processing container 2, within which a circular plate-shaped mounting stage 10 for holding the substrate W is disposed. The processing container 2 is made of metal, such as aluminum or stainless steel. The mounting stage 10 includes a base 11 and an electrostatic chuck 25. The base 11 (mounting stage 10) serves as a lower electrode. The base 11 is made of, for example, aluminum. The base 11 is supported by an insulating cylindrical holding member 12 via a cylindrical support portion 13 extending vertically upward from the bottom of the processing container 2.

[0034] An exhaust passage 14 is formed between the side wall of the processing container 2 and the cylindrical support portion 13. An annular baffle 15 is disposed at the inlet or midway of the exhaust passage 14, and an exhaust port 16 is provided at the bottom. The exhaust port 16 is connected to an exhaust device 18 via an exhaust pipe 17. Here, the exhaust device 18 has a dry pump or a vacuum pump, which can reduce the pressure of the processing space inside the processing container 2 to a specified vacuum level. In addition, the exhaust pipe 17 has an automatic pressure control valve (hereinafter referred to as "APC") composed of an adjustable butterfly valve, which automatically controls the pressure inside the processing container 2. A gate valve 20 for opening and closing the inlet and outlet 19 of the substrate W is also installed on the side wall of the processing container 2.

[0035] The base 11 is connected to a first high-frequency power supply 21a via an impedance transformer 22a. The base 11 is also connected to a second high-frequency power supply 21b via a matching transformer 22b. The first high-frequency power supply 21a supplies the base 11 (stage 10) with high-frequency electrical power at a predetermined frequency (e.g., 40 MHz) for plasma generation. The second high-frequency power supply 21b supplies the base 11 (stage 10) with high-frequency electrical power at a predetermined frequency (e.g., 400 kHz) lower than that of the first high-frequency power supply 21a for ion attraction.

[0036] A spray head 24, which also serves as an upper electrode, is disposed on the top of the processing container 2. As a result, high-frequency voltages of two frequencies from the first high-frequency power supply 21a and the second high-frequency power supply 21b can be applied between the base 11 (stage 10) and the spray head 24.

[0037] An electrostatic chuck 25 is provided on the upper surface of the base 11, capable of adsorbing the substrate W by electrostatic attraction. The electrostatic chuck 25 includes a circular central portion 25a for holding the substrate W, and an annular outer peripheral portion 25b formed around the central portion 25a. The central portion 25a protrudes upward relative to the outer peripheral portion 25b in the figure. The upper surface of the central portion 25a is the substrate mounting surface 25a1 for holding the substrate W. The upper surface of the outer peripheral portion 25b is the edge ring mounting surface 25b1 for holding the edge ring 30. The edge ring mounting surface 25b1 is formed so that the edge ring 30 can be mounted around the substrate mounting surface 25a1. The edge ring 30 is also called a focusing ring. The central portion 25a is formed by sandwiching an electrode plate 26 made of conductive film between a pair of dielectric films. The electrode plate 26 is electrically connected to a DC power supply 27. The outer peripheral portion 25b is formed by sandwiching an electrode plate 29, which is made of a conductive film, between a pair of dielectric films. The electrode plate 29 is electrically connected to a DC power supply 28.

[0038] DC power supplies 27 and 28 can change the magnitude and polarity of the supplied DC voltage. DC power supply 27 applies a DC voltage to electrode plate 26 under the control of control unit 43 (described later). DC power supply 28 applies a DC voltage to electrode plate 29 under the control of control unit 43. The electrostatic chuck 25 uses the voltage applied from DC power supply 27 to electrode plate 26 to generate electrostatic forces such as Coulomb force, and uses these electrostatic forces to adhere and hold the substrate W in the electrostatic chuck 25. Furthermore, the electrostatic chuck 25 uses the voltage applied from DC power supply 28 to electrode plate 29 to generate electrostatic forces such as Coulomb force, and uses these electrostatic forces to adhere and hold the edge ring 30 in the electrostatic chuck 25.

[0039] Furthermore, in the electrostatic chuck 25 of this embodiment, the electrostatic chuck for the substrate W and the electrostatic chuck for the edge ring 30 are integrated, but the electrostatic chuck for the substrate W and the electrostatic chuck for the edge ring 30 can also be separate electrostatic chucks. That is, the electrode plate 26 and the electrode plate 29 can be configured such that they are sandwiched in their respective independent dielectric films. Furthermore, the electrode plate 29 of this embodiment represents an example of a unipolar electrode, but it can also be a bipolar electrode. In the case of a bipolar electrode, the edge ring 30 can be adsorbed even when no plasma is generated.

[0040] Inside the base 11, for example, an annular cooling medium chamber 31 extending in the circumferential direction is provided. A cooling medium, such as cooling water, at a predetermined temperature is circulated from the refrigeration unit 32 through pipes 33 and 34 into the cooling medium chamber 31. The temperature of this cooling medium is used to control the processing temperature of the substrate W on the electrostatic chuck 25. The cooling medium is a temperature-regulating medium circulated in pipes 33 and 34. The temperature-regulating medium can be used not only for cooling the base 11 and the substrate W, but also for heating.

[0041] Furthermore, the electrostatic chuck 25 is connected to the heat transfer gas supply unit 35 via a gas supply line 36. The heat transfer gas supply unit 35 supplies heat transfer gas to the space between the center portion 25a of the electrostatic chuck 25 and the substrate W using the gas supply line 36. As the heat transfer gas, a gas with thermal conductivity, such as He gas, can be appropriately used.

[0042] The spray head 24 on the top plate includes an electrode plate 37 on its lower surface and an electrode support 38 that supports the electrode plate 37 in a detachable manner. The electrode plate 37 has a large number of gas vent holes 37a. A buffer chamber 39 is provided inside the electrode support 38, and a processing gas supply unit 40 is connected to the gas inlet 38a communicating with the buffer chamber 39 via a gas supply pipe 41.

[0043] Each component of the substrate processing apparatus 1 is connected to the control unit 43. For example, the exhaust device 18, the first high-frequency power supply 21a, the second high-frequency power supply 21b, the impedance transformer 22a, the matching device 22b, the DC power supply 27, the DC power supply 28, the cooling unit 32, the heat transfer gas supply unit 35, and the processing gas supply unit 40 are connected to the control unit 43. The control unit 43 controls each component of the substrate processing apparatus 1.

[0044] The control unit 43 includes a central processing unit (CPU) and a memory (not shown), and performs the desired processing in the substrate processing unit 1 by reading and executing programs and processing schemes stored in the memory.

[0045] In the substrate processing apparatus 1, the gate 20 is first opened, and the substrate W to be processed is fed into the processing container 2 and placed on the electrostatic chuck 25. Next, in the substrate processing apparatus 1, processing gas (for example, a mixture of C4F6, C4F8, O2, and Ar gases) is introduced into the processing container 2 at a predetermined flow rate and flow ratio through the processing gas supply unit 40, and the pressure inside the processing container 2 is brought to a predetermined value using the exhaust device 18, etc.

[0046] Furthermore, in the substrate processing apparatus 1, high-frequency electrical power with different frequencies is supplied to the substrate 11 (stage 10) from the first high-frequency power supply 21a and the second high-frequency power supply 21b. The substrate processing apparatus 1 applies a DC voltage to the electrode plate 26 of the electrostatic chuck 25 via the DC power supply 27 to adsorb the substrate W onto the electrostatic chuck 25. Moreover, the substrate processing apparatus 1 applies a DC voltage to the electrode plate 29 of the electrostatic chuck 25 via the DC power supply 28 to adsorb the edge ring 30 onto the electrostatic chuck 25. The processing gas released from the spray head 24 is plasma-enhanced, and the substrate W is etched using free radicals and ions in the plasma.

[0047] <Structure of the first high-frequency power supply 21a and impedance converter 22a for plasma generation>

[0048] Figure 2 This is a block diagram showing the structure of the first high-frequency power supply 21a and impedance converter 22a for plasma generation in the substrate processing apparatus 1 of this embodiment.

[0049] The first high-frequency power supply 21a outputs a first high-frequency electrical power HF (e.g., 40MHz) to the impedance transformer 22a via the high-frequency power supply line 23a. The first high-frequency power supply 21a includes a high-frequency oscillator 60a, a power amplifier 62a, a power control unit 64a, and a power monitor 66a.

[0050] The high-frequency oscillator 60a is an oscillator that generates a sinusoidal wave or fundamental wave of a certain frequency (e.g., 40 MHz) suitable for high-frequency discharge plasma generation. The power amplifier 62a is an amplifier that amplifies the power of the fundamental wave output from the high-frequency oscillator 60a with adjustable gain or amplification rate. The power supply control unit 64a is a control unit that directly controls the high-frequency oscillator 60a and the power amplifier 62a based on control signals from the control unit 43.

[0051] Power monitor 66a detects the high-frequency power on high-frequency power supply line 23a. A directional coupler is provided on high-frequency power supply line 23a. Power monitor 66a detects the power PF1 of the traveling wave propagating forward on high-frequency power supply line 23a, i.e., from the first high-frequency power source 21a to the impedance transformer 22a. Furthermore, power monitor 66a detects the power RF1 of the reflected wave propagating backward on high-frequency power supply line 23a, i.e., from the impedance transformer 22a to the first high-frequency power source 21a. Power monitor 66a outputs the detection results to power control unit 64a and control unit 43. Power control unit 64a uses the detection results for power feedback control.

[0052] Impedance transformer 22a performs impedance transformation. Impedance transformer 22a includes an impedance sensor 70a, an impedance transformation circuit 72a, and a controller 74a. Impedance sensor 70a is a detector that measures the impedance on the load side of the high-frequency power supply line 23a, including the impedance of the impedance transformation circuit 72a. Impedance transformation circuit 72a includes multiple—for example, two—controllable reactor elements (e.g., variable capacitors or variable inductors) connected to the high-frequency power supply line 23a. H1 and X H2 The circuit. Controller 74a, via motor (M) 76a and motor 78a, supplies power to reactor element X. H1 and X H2They are controlled separately. Controller 74a controls motors 76a and 78a so that the impedance detected by impedance sensor 70a becomes the impedance set by control unit 43.

[0053] Stage 10 is an example of a substrate stage.

[0054] <Structure of the second high-frequency power supply 21b and matching device 22b for ion attraction>

[0055] Figure 3 This is a block diagram showing the structure of the second high-frequency power supply 21b and the matching device 22b for ion attraction in the substrate processing apparatus 1 of this embodiment.

[0056] The second high-frequency power supply 21b outputs a second high-frequency electrical power LF at a lower frequency (e.g., 400kHz) than the first frequency (e.g., 40MHz) to the matching unit 22b via the high-frequency power supply line 23b. The second high-frequency power supply 21b includes a high-frequency oscillator 60b, a power amplifier 62b, a power control unit 64b, and a power monitor 66b.

[0057] The high-frequency oscillator 60b is an oscillator that generates a sinusoidal wave or fundamental wave at a certain frequency (e.g., 400 kHz) suitable for ion attraction. The power amplifier 62b is an amplifier that amplifies the power of the fundamental wave output from the high-frequency oscillator 60b with adjustable gain or amplification rate. The power supply control unit 64b is a control unit that directly controls the high-frequency oscillator 60b and the power amplifier 62b based on control signals from the control unit 43.

[0058] Power monitor 66b detects the high-frequency power on high-frequency power supply line 23b. A directional coupler is provided on high-frequency power supply line 23b in power monitor 66b. Power monitor 66b detects the power PF2 of the traveling wave propagating forward on high-frequency power supply line 23b, i.e., from the second high-frequency power supply 21b to the matching unit 22b. Furthermore, power monitor 66b detects the power RF2 of the reflected wave propagating backward on high-frequency power supply line 23b, i.e., from the matching unit 22b to the second high-frequency power supply 21b. Power monitor 66b outputs the detection results to power control unit 64b and control unit 43. Power control unit 64b uses the detection results for power feedback control.

[0059] Matching unit 22b is used to match the impedance of the second high-frequency power supply 21b with the impedance of the base 11 (mount 10). Matching unit 22b includes an impedance sensor 70b, a matching circuit 72b, and a matching controller 74b. Impedance sensor 70b is a detector that measures the impedance on the load side of the high-frequency power supply line 23b, including the impedance of the matching circuit 72b. Matching circuit 72b includes multiple—for example, two—controllable reactor elements (e.g., variable capacitors or variable inductors) connected to the high-frequency power supply line 23b. L1 and X L2 The circuit. Matching controller 74b is connected to reactor element X via motor (M) 76b and motor 78b. L1 and X L2 The control units perform separate control. The matching controller 74b controls the motors 76b and 78b so that the output impedance of the second high-frequency power supply 21b matches the impedance detected by the impedance sensor 70b.

[0060] Impedance Control

[0061] The control of the impedance of the first high-frequency power HF in the substrate processing apparatus 1 of this embodiment will be described. In the substrate processing apparatus 1 of this embodiment, the set value (set impedance) of the impedance to be transformed by the impedance converter 22a connected to the first high-frequency power supply 21a is changed.

[0062] Figure 4 This is a flowchart illustrating the control unit 43 of the substrate processing apparatus 1 in this embodiment. (Using...) Figure 4 The control method of the control unit 43 of the substrate processing apparatus 1 will be described.

[0063] (Step S10) The control unit 43 acquires information about the substrate processing to be performed in the substrate processing apparatus 1. For example, the operator inputs the substrate processing to be performed from an input device such as a keyboard. The control unit 43 acquires the information about the substrate processing to be performed in the substrate processing apparatus 1 input from that input device. Alternatively, the control unit 43 may automatically acquire information about the substrate processing to be performed in the substrate processing apparatus 1 based on a processing scheme or the like.

[0064] (Step S20) The control unit 43 obtains a set value (set impedance) for the impedance corresponding to the content of the substrate processing based on the substrate processing information obtained in step S10. For example, for the substrate processing to be performed, the set value (set impedance) of the impedance suitable for the substrate processing is saved as a table in a storage unit such as a memory. Then, the control unit 43 obtains the set value (set impedance) of the impedance suitable for the substrate processing for the input processing by referring to the table.

[0065] A table storing impedance settings (set impedance) suitable for substrate processing is generated in such a way that, based on the evaluation results of the etching rate and other parameters of the substrate processing performed in the substrate processing apparatus 1, the optimal impedance settings (set impedance) for the substrate processing to be performed are generated.

[0066] (Step S30) The control unit 43 uses the impedance setting value (set impedance) obtained in step S20 to control the impedance converter 22a. Specifically, the control unit 43 controls the controller 74a of the impedance converter 22a to achieve the aforementioned impedance setting value (set impedance).

[0067] Next, the substrate processing apparatus 1 of this embodiment performs substrate processing at a set value (set impedance) corresponding to the substrate processing to be performed.

[0068] The following describes the case where the substrate processing apparatus 1 of this embodiment performs multiple substrate processing operations. For example, the case where the substrate processing apparatus 1 performs a first substrate processing operation and a second substrate processing operation consecutively will be described. In step S10, the control unit 43 of the substrate processing apparatus 1 acquires information about the first and second substrate processing operations to be performed. Next, when the first substrate processing operation is initially performed, the control unit 43 acquires a first set value of impedance corresponding to the content of the first substrate processing operation (step S20). Then, the control unit 43 uses the first set value to control the impedance transformer 22a (step S30). Then, the substrate processing apparatus 1 performs the first substrate processing operation. Next, when the second substrate processing operation is performed, the control unit 43 acquires a second set value of impedance corresponding to the content of the second substrate processing operation (step S20). Then, the control unit 43 uses the second set value to control the impedance transformer 22a (step S30). Then, the substrate processing apparatus 1 performs the second substrate processing operation.

[0069] When the substrate processing apparatus 1 of this embodiment performs multiple substrate processing operations, as described above, the control unit 43 sets a set value (set impedance) for the impedance of each substrate processing operation. Therefore, the substrate processing apparatus 1 performs substrate processing at the set impedance (set impedance) corresponding to each substrate processing operation.

[0070] <Behavior when simultaneously supplying the first high-frequency power HF and the second high-frequency power LF>

[0071] The following describes the behavior of the substrate processing apparatus 1 in this embodiment when a first high-frequency power HF and a second high-frequency power LF are simultaneously supplied to the substrate 11.

[0072] Figure 5This is a diagram conceptually illustrating the waveforms of the first high-frequency power HF and the second high-frequency power LF when the substrate processing apparatus 1 of this embodiment supplies the substrate 11 with the first high-frequency power HF and the second high-frequency power LF. Furthermore, Figure 5 This is a state in which impedance matching has been achieved in the impedance transformer 22a. For example, a state in which the output impedance of the first high-frequency power supply 21a matches the impedance of the impedance transformer 22a as observed from the first high-frequency power supply 21a, including the load generated by the plasma.

[0073] Figure 5 The upper part of (a) represents the waveform of the voltage of the first high-frequency power HF from the first high-frequency power source 21a. The frequency (first frequency) of the first high-frequency power HF is, for example, 40 MHz. Figure 5 The lower part of (a) represents the waveform of the voltage of the second high-frequency power LF from the second high-frequency power source 21b. The frequency (second frequency) of the second high-frequency power LF is, for example, 400 kHz. Figure 5 The middle part of (a) represents the loss of the first high-frequency electrical power HF due to the reflected wave HFPr returning from the base 11 to the first high-frequency power supply 21a. Furthermore, Figure 5 The reflected wave HFPr is conceptually represented by an envelope. This reflected wave HFPr is the power of the reflected wave generated by intermodulation distortion (IMD). This reflected wave HFPr is the electrical power signal returning to the first high-frequency power source 21a, and therefore does not contribute to plasma generation.

[0074] Figure 5 (b) represents the effective power HFPe of the first high-frequency electrical power HF that contributes to the generation of plasma. Figure 5 The upper and lower parts of (b) are with Figure 5 (a) is the same. Figure 5 The middle part of (b) represents the effective power HFPe obtained by subtracting the power of the reflected wave HFPr from the power of the first high-frequency electrical power HF.

[0075] like Figure 5 As shown, with impedance matching achieved in the impedance transformer 22a, when the voltage of the second high-frequency power LF is at its positive or negative peak, the loss of the first high-frequency power HF, i.e., the reflected wave HFPr, is relatively large. On the other hand, when the voltage of the second high-frequency power LF is near zero, the loss of the first high-frequency power HF, i.e., the reflected wave HFPr, is relatively small.

[0076] <Behavior caused by the set impedance of impedance transformer 22a>

[0077] Next, the behavior when the set impedance is changed in the impedance transformer 22a will be explained.

[0078] Figure 6 This diagram conceptually illustrates the effect of the set impedance of the impedance transformer 22a when the substrate processing apparatus 1 in this embodiment supplies the first high-frequency electrical power HF and the second high-frequency electrical power LF to the substrate 11. Figure 6 The figures, from top to bottom, show the waveform of the voltage of the first high-frequency power HF, the effective power HFPe of the first high-frequency power HF, the waveform of the voltage of the second high-frequency power LF, and the loss of the first high-frequency power HF caused by the reflected wave HFPr.

[0079] Figure 6 (b) represents the waveform in the state where impedance matching has been achieved in the impedance transformer 22a. Figure 6 of (a), Figure 6 (c) represents the waveform in the state where impedance matching is not achieved in the impedance transformer 22a.

[0080] like Figure 5 As described in the description, in the state where the impedance is matched ( Figure 6 Under condition (b), when the voltage of the second high-frequency power LF is at its positive or negative peak value, the loss of the first high-frequency power HF, i.e., the reflected wave HFPr, is relatively large. On the other hand, when the voltage of the second high-frequency power LF is near zero, the loss of the first high-frequency power HF, i.e., the reflected wave HFPr, is relatively small. Therefore, in Figure 6 In case (b), the effective power HFPe of the first high-frequency power HF is maximized when the voltage of the second high-frequency power LF is near zero. Conversely, the effective power HFPe of the first high-frequency power HF is minimized when the voltage of the second high-frequency power LF is at its positive or negative peak value.

[0081] On the other hand, in the case of impedance mismatch, the loss of the first high-frequency electrical power HF, i.e. the peak value of the reflected wave HFPr, is different from that in the case of impedance matching.

[0082] exist Figure 6 In case (a), when the voltage of the second high-frequency power LF is at a negative peak, the loss of the first high-frequency power HF, i.e., the reflected wave HFPr, is relatively large. Conversely, when the voltage of the second high-frequency power LF is at a positive peak, the loss of the first high-frequency power HF, i.e., the reflected wave HFPr, is relatively small. Therefore, in Figure 6 In case (a), the effective power HFPe of the first high-frequency power HF is maximized when the voltage of the second high-frequency power LF is at a positive peak value. Conversely, the effective power HFPe of the first high-frequency power HF is smaller when the voltage of the second high-frequency power LF is at a negative peak value.

[0083] exist Figure 6In case (c), when the voltage of the second high-frequency power LF is at a positive peak value, the loss of the first high-frequency power HF, i.e., the reflected wave HFPr, is relatively large. Conversely, when the voltage of the second high-frequency power LF is at a negative peak value, the loss of the first high-frequency power HF, i.e., the reflected wave HFPr, is relatively small. Therefore, in Figure 6 In case (c), the effective power HFPe of the first high-frequency power HF is maximized when the voltage of the second high-frequency power LF is at a negative peak value. Conversely, the effective power HFPe of the first high-frequency power HF is smaller when the voltage of the second high-frequency power LF is at a positive peak value.

[0084] In this way, unlike existing impedance matching methods, by making the impedance mismatched, the timing of the peak value of the reflected wave caused by intermodulation distortion can be changed relative to the voltage of the second high-frequency power LF. For example, by setting the set impedance, the peak value of the reflected wave HFPr can be made to occur when the voltage of the second high-frequency power LF is at a positive or negative peak value.

[0085] Figure 7 , Figure 8 This represents the specific waveform when the impedance setting value (set impedance) is changed. The waveform is obtained by measuring the first high-frequency power HF, the second high-frequency power LF, and the reflected wave HFPr using an oscilloscope while simultaneously changing the set impedance of the impedance transformer 22a. The first high-frequency power HF is the average power measured. The average power of the first high-frequency power HF is constant. Figure 8 In this paper, the set value of impedance (set impedance) is plotted on the coordinate axis of set resistance and set reactance described later, and the waveforms associated with the set value are summarized.

[0086] Furthermore, the set impedance of impedance transformer 22a is summarized in Table 1. The set impedance is represented by the difference between the resistance and reactance relative to the matched state. Therefore, under the matched condition A, the set resistance and set reactance are zero.

[0087] Table 1

[0088] condition Set the resistance (Ω) Set reactance (Ω) Condition A (Matching Status) 0 0 Condition B ﹣3.8 19.2 Condition C ﹣13.7 ﹣10.7 Condition D ﹣13.7 10.7 Condition E ﹣16.7 0 Condition F ﹣3.8 ﹣19.2 ConditionG 13.4 ﹣18.7 Condition H 25 0 Condition I 13.4 18.7

[0089] Due to the influence of the set impedance of the impedance transformer 22a, the peak time of the reflected wave HFPr is different from the voltage (phase) of the second high-frequency power LF.

[0090] For example, in Figure 7 In condition A of (a), i.e., under the matched state, when the voltage of the second high-frequency power LF is at its positive or negative peak, the reflected wave HFPr is relatively large. Figure 7 Under condition B of (b), when the voltage of the second high-frequency power LF is at a negative peak, the reflected wave HFPr is smaller. Figure 7 Under condition C of (c), when the voltage of the second high-frequency power LF is positive, the reflected wave HFPr is smaller.

[0091] Figure 9 This indicates the electron density of the plasma when the set impedance of the impedance converter 22a is changed. Figure 9 The horizontal axis of the coordinate graph represents time. Figure 9 The horizontal axis of the coordinate graph corresponds to one cycle of the second high-frequency electrical power LF. Figure 9 The vertical axis of the coordinate graph represents the electron density of the plasma.

[0092] according to Figure 9 As a result, by using condition B as the set impedance of impedance transformer 22a, the electron density of the plasma can be increased.

[0093] and then, Figure 10 This indicates the etching rate of silicon oxide when the set impedance of impedance transformer 22a is changed. Figure 10 The vertical axis of the coordinate graph represents the etching rate.

[0094] according to Figure 10 As a result, by using condition B as the set impedance of impedance transformer 22a, the etching rate can be improved.

[0095] Here, an impedance suitable for the substrate processing to be performed is described. The substrate processing apparatus 1 of this embodiment sets a set value (set impedance) for the impedance so that the peak value of the reflected wave is within a predetermined period relative to the voltage (phase) of the second high-frequency electrical power LF.

[0096] First, consider, for example, the case of performing an etching process with a high etching rate. As described above, in the substrate processing apparatus 1, when a first high-frequency electrical power is supplied under the impedance of condition B, the electron density of the plasma can be increased. Furthermore, the etching rate can be increased. Therefore, for etching processes with high etching rates, condition B is set as an impedance suitable for substrate processing. Specifically, the set value of the impedance (set impedance) is such that the reflected wave becomes a peak during the period when the voltage of the second high-frequency electrical power LF is negative, especially during the period near the negative peak of the voltage of the second high-frequency electrical power LF. By supplying the first high-frequency electrical power HF under the impedance of condition B, more ions can react at high energy, thus promoting etching during processing.

[0097] Next, consider, for example, the case where highly selective etching is required (e.g., the case where the etching process is selected based on the etching depth). In the substrate processing apparatus 1, when the first high-frequency electrical power HF is supplied under the impedance of condition C, the surface adhesion of ions and free radicals and the high-energy reaction of ions will repeatedly occur.

[0098] The specific processing is explained below. When the voltage of the second high-frequency power LF is at its positive peak, the effective power of the first high-frequency power HF is relatively high, thus promoting the dissociation of the reactant gas and increasing the number of ions and free radicals. Subsequently, as the dissociation of ions and free radicals is promoted, since the voltage of the second high-frequency power LF is at its positive peak, the dissociated free radicals will adhere to the surface layer. The types of dissociated ions and free radicals vary depending on the power supplied by the first high-frequency power HF. For example, when using C4F6 as the etching gas, when the power supplied by the first high-frequency power HF is relatively low, most free radicals with low dissociation degree and high adhesion coefficient (e.g., C4F6) are generated. x F y High-adhesion-coefficient free radicals adhere to the surface of the object being processed, thus serving, for example, as a protective mask. On the other hand, when the supplied first high-frequency electrical power HF is high, it generates mostly free radicals with high dissociation and low adhesion coefficients (e.g., CF2, CF, CF3, etc.). These low-adhesion-coefficient free radicals can be transported to the bottom of the etched shape, thus contributing more to the etching process. Therefore, when the voltage of the second high-frequency electrical power LF is at a negative peak, dissociated ions are supplied to the bottom, promoting etching. As described above, the surface adhesion of ions and free radicals and the high-energy reaction of ions occur repeatedly according to the cycle of the second high-frequency electrical power LF.

[0099] As described above, by setting the impedance such that the reflected wave is larger when the voltage of the second high-frequency power LF is negative, selective etching can be performed by utilizing the difference in adhesion coefficients of ions and free radicals. Therefore, for selective etching, setting condition C is used as the impedance suitable for substrate processing. Specifically, the set impedance value (set impedance) is such that the reflected wave reaches its peak value during the period when the voltage of the second high-frequency power LF is positive, especially during the period near the positive peak value of the second high-frequency power LF.

[0100] Furthermore, the impedance suitable for substrate processing is not limited to conditions B and C. For example, by selecting other conditions, it is also possible to perform etching with intermediate characteristics of substrate processing under conditions B and C respectively.

[0101] <Function / Effect>

[0102] Using the substrate processing apparatus 1 of this embodiment, in a plasma processing apparatus, the timing of the power supplied by the first high-frequency electric power for plasma generation can be adjusted relative to the voltage (phase) of the second high-frequency electric power LF used for attraction. That is, by setting the impedance of the impedance converter 22a of the substrate processing apparatus 1 of this embodiment to a mismatched state, the generation time of the reflected wave can be changed relative to the voltage (phase) of the second high-frequency electric power LF. Furthermore, by changing the generation time of the reflected wave relative to the voltage (phase) of the second high-frequency electric power LF, the timing of supplying the first high-frequency electric power to the plasma at high power can be adjusted relative to the voltage (phase) of the second high-frequency electric power LF. Therefore, using the substrate processing apparatus 1 of this embodiment, an impedance suitable for processing can be set.

[0103] The substrate processing apparatus of this embodiment disclosed herein is merely illustrative in all respects and should not be considered limiting. The above embodiments can be modified and improved in various ways without departing from the scope and spirit of the appended claims. The contents described in the above embodiments can be employed in other structures and combined with each other without contradiction.

[0104] The substrate processing apparatus of the present invention can be applied to any type of plasma, such as capacitively coupled plasma (CCP), inductively coupled plasma (ICP), plasma generated using a microwave-based plasma generation device—such as a radial line slot antenna (RLSA)—microwave electron cyclotron resonance plasma (ECR), and helical wave plasma (HWP).

Claims

1. A substrate processing apparatus, characterized in that, include: A substrate mounting stage for placing substrates; A first high-frequency power supply provides a first high-frequency electrical power of a first frequency to the substrate mounting stage. An impedance transformer that transforms the load-side impedance observed from the first high-frequency power supply into a set set impedance. A second high-frequency power supply provides the substrate mounting stage with a second high-frequency electrical power at a second frequency lower than the first frequency; and The control unit controls the set impedance of the impedance transformer. The control unit sets the set impedance according to the substrate processing, such that the peak value of the reflected wave propagating from the impedance transformer to the first high-frequency power supply is during the period when the voltage of the second high-frequency power supply is negative.

2. The substrate processing apparatus as described in claim 1, characterized in that: The control unit sets the set impedance based on the electron density of the plasma.

3. The substrate processing apparatus as described in claim 1, characterized in that: The control unit sets the set impedance based on the etching rate.

4. The substrate processing apparatus as described in claim 1, characterized in that: The control unit sets the set impedance based on the etching depth.

5. The substrate processing apparatus as described in claim 1, characterized in that: The control unit sets the set impedance such that the peak value of the reflected wave propagating from the impedance transformer to the first high-frequency power supply is within a predetermined period relative to the voltage of the second high-frequency power supply.

6. The substrate processing apparatus according to any one of claims 1 to 5, characterized in that: The control unit sets the set impedance for each of the multiple substrate processes.

7. A control method for a substrate processing apparatus, characterized in that: The substrate processing apparatus includes: A substrate mounting stage for placing substrates; A first high-frequency power source generates first high-frequency electrical power at a first frequency. An impedance transformer is used to input the first high-frequency power to the impedance transformer, which transforms the impedance on the load side observed from the first high-frequency power supply into a set impedance and outputs it to the substrate mounting stage. A second high-frequency power supply generates a second high-frequency electrical power at a lower frequency than the first frequency, and outputs it to the substrate mounting stage; and The control unit controls the set impedance of the impedance transformer. The control method includes: The step of the control unit setting the set impedance according to the substrate processing, such that the peak value of the reflected wave propagating from the impedance transformer to the first high-frequency power supply is during the period when the voltage of the second high-frequency power supply is negative.

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