Plasma treatment equipment, control methods, computer programs and power supply systems

Abstract

The object of this invention is to control the quantity and quality of free radicals and ions. To achieve the above object, this invention provides a control method for a plasma processing apparatus having a first electrode on which a subject is placed, characterized by comprising: a step of supplying bias power to the first electrode; and a step of supplying a source power having a frequency higher than the bias power to a plasma processing space; the source power having a first state and a second state; the control method further comprising: a first control step of interactively applying the first state and the second state in a manner synchronized with the phase of a reference electrical state representing any one of the voltage, current, or electromagnetic field measured by the power supply system of the bias power within one cycle.

Description

[Technical Field]

[0001] This case relates to a control method and a plasma treatment apparatus. [Previous Technology]

[0002] During etching, the technique of synchronizing the on / off states of the applied high-frequency power for ion attraction and the high-frequency power for plasma generation to ensure ions reach the polycrystalline silicon layer and thus achieve a uniform etching rate is well known (see, for example, Patent Document 1). [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-64915 [Summary of the Invention]

[0004] [Problem to be solved by the invention] In Patent Document 1, two high-frequency powers with different frequencies, namely high-frequency power for plasma generation (i.e., source power) and high-frequency power for ion attraction (i.e., bias power), are applied to the processing container to control the etching rate.

[0005] This case provides a technique for controlling the quantity and quality of free radicals and ions. [Means of Problem Solving]

[0006] According to an embodiment disclosed in this application, a control method for a plasma processing apparatus having a first electrode on which a workpiece is disposed is provided, characterized by comprising: a step of supplying bias power to the first electrode; and a step of supplying a source power having a frequency higher than the bias power to a plasma processing space; the source power having a first state and a second state; the control method further comprising: a first control step of interactively applying the first state and the second state in a manner synchronized with the phase of a synchronization signal representing the high-frequency period of the bias power or within a period of a reference electrical state of any one of the voltage, current, or electromagnetic field measured by the power supply system of the bias power. [Effects of the Invention]

[0007] According to an embodiment of the present invention, the quantity and quality of free radicals and ions can be controlled.

Implementation Method

[0009] The embodiments for carrying out the present invention will now be described with reference to the drawings. Furthermore, in this specification and the drawings, substantially the same reference numerals will be used for substantially the same structures, and repeated descriptions will be omitted.

[0010] Hereinafter, the frequency (high frequency) of the source power will also be referred to as "HF" (High Frequency), and the source power will also be referred to as "HF power". In addition, the frequency (high frequency) of the bias power, which is lower than the frequency of the source power, will also be referred to as "LF" (Low Frequency), and the bias power will also be referred to as "LF power".

[0011] [Introduction] If two high-frequency powers with different frequencies are applied to the processing container, namely the high-frequency power for plasma generation (i.e., source power) and the high-frequency power for ion attraction (i.e., bias power), IMD (Intermodulation distortion) may sometimes occur as reflected wave power.

[0012] IMD not only causes mismatch, but also requires a high-frequency power supply with a capacitor that can hold more power than is originally necessary in order to maintain reflection resistance and plasma. Therefore, in the past, in order to reduce the occurrence of IMD, a step was taken to optimize the cable length of the coaxial cable used for the power supply line of the high-frequency power supply.

[0013] However, IMD occurs at frequencies of the sum or difference between the fundamental and / or higher harmonics of HF power and the fundamental and / or higher harmonics of LF power. Therefore, in methods that optimize the cable length of the coaxial cable, even if the reflected power of high-frequency power at a specific frequency can be reduced, the reflected power of other frequencies contained in IMD, which are generated from the sum or difference of the fundamental and / or higher harmonics of HF and LF power, cannot be eliminated.

[0014] Furthermore, we believe that the lower the frequency of the LF power, the more likely IMD will occur near the fundamental frequency of the HF power. Therefore, the frequency of the LF power should be increased as much as possible to suppress IMD near the fundamental frequency of the HF power. However, in recent years, especially in high aspect ratio etching processes, lowering the frequency of the LF power has yielded better results. That is, the deeper the high aspect ratio hole is etched, the lower the etching rate will be. Therefore, this is achieved by using a lower frequency for the LF power and increasing the power. This allows for an increase in the etching rate in high aspect ratio etching steps. However, under these conditions, IMD will increase further. Therefore, the recent trend of high power and low frequency of LF power has led to an increase in the reflected power of the high-frequency power. In particular, when LF power and HF power are applied to the same electrode, the reflected power of the high-frequency power increases.

[0015] For example, Figure 12 shows an example of the reflected wave power that occurs when an HF power of a predetermined frequency is applied to an electrode that has already been charged with LF power. The intensity of IMD varies periodically in sync with the phase of Vpp (Peak to Peak) of LF. For example, in the example of Figure 12, near the maximum positive potential of LF, IMD is approximately 0W, that is, in a state where no reflection occurs. In addition, IMD is relatively low in the range where the potential of LF is negative. When the potential of LF exceeds the maximum positive value and then moves towards the negative value, the maximum reflected wave power occurs, and IMD is at its maximum.

[0016] Therefore, the inventors of this case propose a control method for suppressing the occurrence of IMD by considering the timing of IMD occurrence and corresponding to the phase of LF, as well as a plasma processing apparatus for implementing this control method. Furthermore, the inventors of this case propose a control method for controlling the quantity and quality of free radicals and ions by controlling high-frequency electric current of two different frequencies, LF and HF.

[0017] [Overall Structure of the Plasma Processing Apparatus] First, an example of an embodiment of the plasma processing apparatus 1 will be described with reference to FIG1. ​​FIG1 is a diagram showing an example of an embodiment of the plasma processing apparatus.

[0018] One embodiment of the plasma treatment apparatus 1 is a capacitively coupled parallel plate plasma treatment apparatus, for example having a cylindrical treatment container 10 made of aluminum with an anodized surface. The treatment container 10 is grounded.

[0019] At the bottom of the processing container 10, a cylindrical support stage 14 is disposed across an insulating plate 12 made of ceramic or the like, and a mounting stage 16 made of aluminum is disposed on the support stage 14, for example. The mounting stage 16 constitutes the lower electrode, and the object to be processed (e.g., a wafer W) is mounted on it across an electrostatic chuck 18.

[0020] An electrostatic chuck 18 is provided on the top surface of the stage 16 to attract and hold the wafer W by electrostatic force. The electrostatic chuck 18 has a structure in which an electrode 20 made of a conductive film is clamped by a pair of insulating layers or insulating sheets. The electrode 20 is connected to a DC power supply 22. The DC voltage output by the DC power supply 22 is applied to the electrode 20. The electrostatic force, such as the Coulomb force generated therefrom, attracts and holds the wafer W in the electrostatic chuck 18.

[0021] On the mounting stage 16, a conductive edge ring 24 made of silicon is disposed around the wafer W, for example. The edge ring 24 is also called a focusing ring. On the sides of the mounting stage 16 and the support stage 14, cylindrical inner wall members 26 made of quartz are provided, for example.

[0022] Inside the support stage 14, for example, an annular refrigerant chamber 28 is provided. Refrigerant (e.g., cooling water) at a predetermined temperature is circulated from an external cooling unit to the refrigerant chamber 28 via pipes 30a and 30b, and the temperature of the refrigerant is used to control the processing temperature of the wafer W on the mounting stage 16. Furthermore, the refrigerant is an example of a temperature-regulating medium circulated and supplied by pipes 30a and 30b; this temperature-regulating medium is sometimes used for heating in addition to cooling the mounting stage 16 and the wafer W.

[0023] Furthermore, a heat-conducting gas, such as He gas, from the heat-conducting gas supply mechanism is supplied through the gas supply line 32 to the area between the top surface of the electrostatic chuck 18 and the back surface of the wafer W.

[0024] Above the mounting stage 16, an upper electrode 34 is disposed parallel to the mounting stage 16 and facing each other. The space between the upper electrode 34 and the lower electrode is called the plasma processing space. The upper electrode 34 forms a surface that faces the wafer W on the mounting stage 16 and is in contact with the plasma processing space, i.e., an opposing surface.

[0025] The upper electrode 34 is supported at the top of the processing container 10 by an insulating shielding member 42. The upper electrode 34 includes: an electrode plate 36 forming a surface facing the stage 16 and having a plurality of gas discharge holes 37; and an electrode support 38 that supports the electrode plate 36 in a removable manner and is made of a conductive material (e.g., anodized aluminum). The electrode plate 36 may also be formed of silicon or SiC, for example. Inside the electrode support 38, a gas diffusion chamber 40 is provided, and a plurality of gas passage holes 41 extend downward from the gas diffusion chamber 40 and communicate with the gas discharge holes 37.

[0026] A gas inlet 62 is formed on the electrode support 38 to guide the processing gas to the gas diffusion chamber 40. This gas inlet 62 is connected to a gas supply pipe 64, which is connected to a processing gas supply source 66. A mass flow controller (MFC) 68 and an on / off valve 70 are sequentially arranged from the upstream side of the gas supply pipe 64. Then, the etching processing gas is supplied from the processing gas supply source 66. The processing gas flows from the gas supply pipe 64 to the gas diffusion chamber 40 and is discharged in a shower-like manner from the gas discharge port 37 through the gas flow passage 41 into the plasma processing space. Thus, the upper electrode 34 functions as a spray head for supplying the processing gas.

[0027] The upper electrode 34 is connected to the variable DC power supply 50, and a DC voltage from the variable DC power supply 50 is applied to the upper electrode 34. The polarity, current, and voltage of the variable DC power supply 50, as well as the control of the electronic switch that turns the current or voltage on or off, are controlled by the control unit 200.

[0028] The stage 16 is connected to the first high-frequency power supply 48 via a power supply bar 47 and a matching adapter 46. The first high-frequency power supply 48 applies LF power to the stage 16. This attracts ions to the wafer W on the stage 16. The first high-frequency power supply 48 outputs LF power at frequencies ranging from 200 kHz to 13.56 MHz. The matching adapter 46 matches the internal impedance of the first high-frequency power supply 48 with the load impedance.

[0029] The mounting platform 16 is connected to the second high-frequency power supply 90 via a power supply rod 89 and a matching device 88. The second high-frequency power supply 90 applies HF power to the mounting platform 16. The frequency of HF is higher than that of LF, and the second high-frequency power supply 90 outputs HF power at a frequency of 13.56MHz or higher. For example, compared to 400kHz LF power, HF power at a higher frequency of 100MHz can be output. The matching device 88 matches the internal impedance of the second high-frequency power supply 90 with the load impedance. The mounting platform 16 can also be connected to a filter 94 for predetermined high-frequency grounding. In addition, the HF power supplied by the second high-frequency power supply 90 can also be applied to the upper electrode 34.

[0030] An exhaust port 80 is provided at the bottom of the processing container 10, and the exhaust port 80 is connected to an exhaust device 84 through an exhaust pipe 82. The exhaust device 84 is a vacuum pump, such as a turbomolecular pump, which can reduce the pressure inside the processing container 10 to the desired vacuum level. In addition, a wafer W loading / unloading port 85 is provided on the side wall of the processing container 10, and the loading / unloading port 85 can be opened or closed by a gate valve 86. In addition, a deposit baffle 11 is provided along the inner wall of the processing container 10 in a removable manner to prevent etching by-products (deposits) from adhering to the processing container 10. That is, the deposit baffle 11 constitutes the wall of the processing container. In addition, the deposit baffle 11 is also provided around the outer periphery of the inner wall member 26. An exhaust plate 83 is provided between the deposit baffle 11 on the wall side of the processing container at the bottom of the processing container 10 and the deposit baffle 11 on the inner wall member 26 side. Components made of aluminum coated with ceramics such as Y2O3 can be used as deposit baffles 11 and exhaust plates 83.

[0031] When etching is to be performed in the plasma processing apparatus 1 with the aforementioned structure, firstly, the gate valve 86 is opened, and the wafer W to be etched is loaded into the processing container 10 via the loading / unloading outlet 85 and placed on the loading stage 16. Then, the etching processing gas is supplied to the gas diffusion chamber 40 at a predetermined flow rate from the processing gas supply source 66, and is supplied into the processing container 10 via the gas flow port 41 and the gas discharge port 37. In addition, the gas in the processing container 10 is discharged using the exhaust device 84, so that the pressure therein is set to a value, for example, in the range of 0.1 to 150 Pa. Here, various conventionally used gases can be used as the processing gas, and for example, a halogen-containing gas such as C4F8 is preferred. Furthermore, other gases such as Ar or O2 may also be used.

[0032] With the etching gas introduced into the processing container 10 as described above, HF power is applied to the stage 16 from the second high-frequency power supply 90. Additionally, LF power is applied to the stage 16 from the first high-frequency power supply 48. Furthermore, a DC voltage is applied to the upper electrode 34 from the variable DC power supply 50. Additionally, a DC voltage is applied to the electrode 20 from the DC power supply 22, thereby holding the wafer W in place on the stage 16.

[0033] The processing gas emitted from the gas emission port 37 of the upper electrode 34 is mainly dissociated and ionized by HF electricity to generate plasma. The processed surface of the wafer W is etched due to free radicals or ions in the plasma. In addition, by applying LF electricity to the stage 16, the ions in the plasma can be controlled to expand the plasma control margin that allows for etching holes with high aspect ratios.

[0034] A control unit 200 is provided in the plasma processing apparatus 1 to control the overall operation of the apparatus. The control unit 200 performs desired plasma processing, such as etching, according to a formula stored in memory such as ROM (Read Only Memory) and RAM (Random Access Memory). The formula sets apparatus control information relative to program conditions, such as program time, pressure (gas exhaust), high-frequency power or voltage, various gas flow rates, temperature inside the processing container (top electrode temperature, sidewall temperature of the processing container, wafer W temperature, electrostatic chuck temperature, etc.), and temperature of the coolant output from the cooler. In addition, the formula indicating these programs or processing conditions can also be stored on a hard drive or semiconductor memory. Furthermore, the formula can also be set to a predetermined location and read when stored in a portable computer-readable recording medium such as a CD-ROM or DVD.

[0035] The switching on / off state or high / low level of the HF power can also be controlled by synchronizing the phase of the high-frequency periodic synchronization signal of the bias power or the phase of any one of the voltage, current, or electromagnetic field measured in the bias power supply system within one cycle. For example, the control unit 200 can also control the switching on / off state or high / low level of the HF power with the phase of the voltage or current of the LF within one cycle. This allows control over the quantity and quality of ions and free radicals. Furthermore, it reduces the occurrence of IMD.

[0036] The bias power supply system refers to the first high-frequency power supply 48 → matching unit 46 → power supply rod 47 → stage 16 → (plasma) → upper electrode 34 → (ground). Any one of the voltage, current or electromagnetic field measured in the bias power supply system refers to the voltage, current or electromagnetic field measured from the first high-frequency power supply 48 through the matching unit 46 and the part of the power supply rod 47 to the stage 16 and the upper electrode 34.

[0037] In addition, the state of the signal that is periodically synchronized with the bias power, or any one of the voltage, current or electromagnetic field measured in the bias power supply system, is called the "reference electrical state". HF power (source power) is controlled in a manner that is "phase-synchronized with the reference electrical state within one cycle and applied alternately with the first state and the second state described later".

[0038] Wherein, when any one of the voltage, current or electromagnetic field measured in the bias power supply system is taken as the "reference electrical state", the reference electrical state shall preferably be any one of the voltage, current or electromagnetic field measured in any one of the components inside the matching unit connected from the mounting platform 16 to the matching unit connected via the power supply rod 47.

[0039] Regarding the method for determining the reference electrical state in a bias power supply system, one example is a method in which a voltage probe, a current probe, or a BZ probe (a probe for measuring induced magnetic fields) is placed near any component of the bias power supply system to measure the voltage, current, or induced magnetic field of each component.

[0040] For example, Figure 2B(a) shows an example where any one of the voltage, current, or electromagnetic field measured in a bias power supply system is taken as the "reference electrical state". For example, in Figure 2B(a), the processor 100 receives any one of the voltage or current of HF, the voltage or current of LF, the phase signal of HF, or the phase signal of LF from a sensor such as a VI probe installed in the power supply system. The processor 100 applies source power alternately in a first state and a second state, synchronized with the phase of the reference electrical state representing any one of the input voltage or current of HF, the voltage or current of LF, the phase signal of HF, or the phase signal of LF within one cycle.

[0041] The processor 100 may also generate a signal that is periodically synchronized with the high frequency of the bias power output from the first high-frequency power supply 48 without relying on the signal from the sensor. In this case, the state of the signal can be used as a reference electrical state. Furthermore, the step of determining the reference electrical state in the bias power supply system can be omitted. For example, in FIG2B(b), the processor 100 receives a signal from the first high-frequency power supply 48 containing information about the phase signal (small power waveform) of LF or the bias power, and generates a signal that is periodically synchronized with the high frequency of the bias power based on the input signal. The processor 100 outputs the generated signal to the second high-frequency power supply 90. The second high-frequency power supply 90 applies source power alternately in a first state and a second state based on the signal.

[0042] Alternatively, the processor 100 may generate a signal with a high-frequency period synchronized with the bias power without relying on the signal from the first high-frequency power supply 48. In this case, the processor 100 generates a signal with a period, for example, as shown in LF in FIG3, and simultaneously generates an ON / OFF signal synchronized with this signal, for example, as shown in HF in FIG3. The processor 100 outputs the generated signal to the first high-frequency power supply 48 and the second high-frequency power supply 90. The first high-frequency power supply 48 outputs bias power according to the signal. The second high-frequency power supply 90 applies source power alternately in a first state and a second state according to the signal.

[0043] Furthermore, the mounting stage 16 is an example of a first electrode on which the wafer W is mounted. The upper electrode is an example of a second electrode facing the first electrode. The first high-frequency power supply 48 is an example of a bias power supply that supplies LF power to the first electrode. The second high-frequency power supply 90 is an example of a source power supply that supplies HF power at a higher frequency than LF power to the first or second electrode. The control unit 200 is an example of a control unit that controls the bias power supply and the source power supply. The potential of the lower electrode (mounting stage 16) to which bias power is applied is also referred to as the electrode potential.

[0044] [Structure of the Control Unit] The specific structure of the control unit 200 will be described with reference to FIG2A. The control unit 200 includes: a processor 100, a signal generation circuit 102, directional couplers 105 and 108, a reflection detector 111, and an oscilloscope 112.

[0045] A directional coupler 105 is connected between the first high-frequency power supply 48 and the matching unit 46 on the power supply line of the first high-frequency power supply 48. A directional coupler 108 is connected between the second high-frequency power supply 90 and the matching unit 88 on the power supply line of the second high-frequency power supply 90.

[0046] Directional coupler 105 assigns a portion of the traveling wave power (Pf) of the LF to the oscilloscope 112. In addition, directional coupler 108 assigns a portion of the traveling wave power and the reflected wave power of the HF to the oscilloscope 112.

[0047] In one embodiment, the oscilloscope 112 displays the frequency of LF, for example, 400kHz, and the frequency of HF, for example, 100MHz. Thus, the waveforms of the traveling wave power of LF, the traveling wave power of HF, and the reflected wave power of HF can be observed on the oscilloscope 112.

[0048] Additionally, the directional coupler 108 separates a certain proportion of the reflected HF wave and assigns it to the reflection detector 111. The reflection detector 111, for example, is composed of a spectrum analyzer, a power meter, etc., and measures the degree to which IMD (Intermodulation Distortion) occurs at what wavelength or what level of reflected wave power. IMD refers to the reflected wave power from the plasma side generated by the sum or difference of the fundamental wave and / or higher harmonics of LF and the fundamental wave and / or higher harmonics of HF, produced by applying HF power to the upper electrode or lower electrode of the plasma processing apparatus 1 (in one embodiment, the lower electrode) and applying LF power to the lower electrode.

[0049] The directional coupler 105 assigns a portion of the traveling wave power of the LF to the processor 100. The processor 100 generates a synchronization signal for HF that is synchronized with the traveling wave power of the LF. For example, the processor 100 may also generate a synchronization signal for HF that is synchronized with the positive timing of the traveling wave of the LF. Alternatively, instead of the directional coupler 105, the waveform of the LF detected by a sensor such as a VI probe may be assigned to the processor 100.

[0050] The processor 100 applies the generated synchronization signal to the signal generation circuit 102. The signal generation circuit 102 generates a control signal that is synchronized with the traveling wave power of the LF based on the applied synchronization signal, and applies it to the second high-frequency power supply 90 and the first high-frequency power supply 48.

[0051] There are two methods for generating the control signal. When the first high-frequency power supply 48 is a general power supply, the directional coupler 105 extracts a portion of the voltage or current of the LF output by the first high-frequency power supply 48 as a waveform and inputs it into the processor 100. However, it is not limited to this; the processor 100 can also directly input a portion of the power of the LF from the first high-frequency power supply 48. The processor 100 generates an ON signal with arbitrary delay and arbitrary amplitude based on the signal of the input waveform and sends it to the signal generation circuit 102. The ON signal is an example of a synchronization signal.

[0052] During the ON signal period, the signal generation circuit 102 sends a command signal to the second high-frequency power supply 90 to generate HF power. The command signal, in accordance with the input state of the second high-frequency power supply 90, uses either a control signal to generate HF power or the ON signal itself during the ON signal period.

[0053] When the first high-frequency power supply 48 is an amplifier that amplifies the power, voltage, or current of the LF, the signal from the directional coupler 105 may not be used. Instead, the signal generation circuit 102 extracts a portion of the power of the LF output by the first high-frequency power supply 48 as a waveform, and generates an ON signal with arbitrary delay and amplitude based on the waveform signal. The signal generation circuit 102 sends the waveform signal and the ON signal to the second high-frequency power supply 90.

[0054] However, the above method of generating control signals is only one example and is not limited thereto. As long as a control signal can be generated based on the given synchronization signal to control the conduction (ON), cut-off (OFF), or high level (High) and low level (Low) of HF power in a manner that is synchronously and interactively applied with the phase of the reference electrical state (the phase of the voltage or current of LF in one cycle, electrode potential, etc.) within one cycle, the circuit of the control unit 200 shown in FIG2A is not limited to that of the control unit 200 shown in FIG2A, and other hardware or software can be used.

[0055] The amplifier of the first high-frequency power supply 48 amplifies the amplitude of the 400kHz LF modulation signal and supplies it to the lower electrode. The amplifier of the second high-frequency power supply 90 amplifies the amplitude of the 100MHz HF modulation signal and supplies it to the lower electrode.

[0056] Figure 3 is a diagram showing an example of the voltage or current waveform of LF and the applied voltage or current of HF when the voltage or current of LF is positive. When the electrode potential shown in the second waveform from the bottom is positive, the voltage or current of HF is controlled to be positive [ON]. When the electrode potential is negative, the voltage or current of HF is controlled to be 0 [OFF]. Basically, the voltage or current of LF determines the electrode potential, so when the voltage or current of LF is negative, the voltage or current of HF is OFF; when the voltage or current of LF is positive, the voltage or current of HF is ON.

[0057] The processor 100 may also generate a synchronization signal for controlling the power of the HF during a time band including the time when the electrode potential is positive. However, the processor 100 is not limited to this, and may also generate a synchronization signal for controlling the power of the HF during a short time including the time when the electrode potential is most negative.

[0058] [Power Supply Timing of HF] Next, the power supply timing of an embodiment of the HF will be explained with reference to FIG4. FIG4 is a diagram showing an example of the power supply timing of an embodiment of the HF.

[0059] The vertical axis of Figures 4(a) to (c) represents the electrode potential. The electrode potential is approximately the same as the wafer potential. The electrode potential is the potential when the voltages of LF and HF overlap. Here, the Vpp of the LF voltage at a frequency of 400 kHz is much larger than the Vpp of the HF voltage at a frequency of 100 MHz. Therefore, basically, the voltage of LF determines the electrode potential and oscillates with the amplitude of the HF voltage Vpp.

[0060] Regarding the sheath layer on the electrode, the thickness of the sheath layer is basically determined according to the voltage of the LF. The electrode potential when the voltage of the LF is negative is because the so-called self-bias voltage Vdc is more negative than the electrode potential when the voltage of the LF is positive. When the electrode potential is positive relative to the ground potential, it is very close to the plasma potential, so a portion of the high-speed electrons may flow into the electrode, and when it is negative relative to the ground potential, ions will flow in.

[0061] Because the electrode is floated from the ground by a blocking capacitor (a matching capacitor in one embodiment), electrons flowing into the electrode do not flow to the ground. Therefore, electrons flow into the electrode and gradually accumulate relative to the plasma during a period (half-cycle) when the electrode is at a positive potential. However, due to the accumulated electrons, the electrode surface becomes negatively charged, generating a negative bias relative to the plasma. Because of this negative bias, ions flow into the electrode surface. Therefore, a sheath layer forms on the electrode surface.

[0062] Finally, the surface of the electrode approaches the plasma potential. At this time, the DC component of the electrode potential when the incoming electrons and the normally incoming ions due to the negative bias voltage are in equilibrium is the self-bias voltage Vdc.

[0063] Figure 3 schematically represents the electrode potential corresponding to the phase of LF, the plasma potential corresponding to the phase of LF, the sheath thickness, and the impedance Z. The plasma potential is slightly higher than the highest potential within the processing container 10. Therefore, the plasma potential is slightly higher than the electrode potential when the electrode potential is positive, and slightly higher than the potential 0 of the wall surface of the processing container 10 when the electrode potential is negative.

[0064] Because of the self-bias voltage Vdc, when the voltage of LF is negative, the electrode potential will be deeply negative. At this time, since the thickness of the sheath is proportional to the voltage, a large voltage is applied to the electrode when the electrode potential is negative, and the thickness of the sheath will increase. In contrast, when the electrode potential is positive, a smaller voltage is applied to the electrode compared to when the electrode potential is negative, and the thickness of the sheath will decrease.

[0065] In one embodiment, LF power and HF power are applied to the stage 16 (lower electrode), so the electrode potential shown in FIG4 is the potential of the lower electrode. Corresponding to the phase of LF, the thickness of the sheath layer on the stage 16 exhibits a timing sequence of a relatively thin state with a roughly flat sheath layer and a timing sequence of a relatively thick sheath layer. Therefore, if the sheath layer is assumed to be a capacitor, the capacitance increases when the sheath layer is thinner, and since the impedance Z = 1 / ωC, the impedance Z of the sheath layer decreases. That is, when the electrode potential is positive, the sheath layer is thinner, so the impedance Z is lower and approximately constant. On the other hand, when the electrode potential is negative, the sheath layer is thicker, so the impedance Z is higher and varies more. Furthermore, the impedance Z is roughly determined by the voltage of LF. Based on the above, the difficulty of impedance matching for HF power increases. In particular, when the electrode potential is negative, that is, when the voltage of LF is negative, the impedance is higher and varies more, thus increasing the difficulty of impedance matching for HF power.

[0066] Regarding the variation of such impedance Z, the matching device 88, which performs impedance matching relative to the HF power, can follow the frequency up to about 1 Hz using the operation of the motor. However, if the frequency is higher, it becomes very difficult to follow and achieve matching, and it becomes a timing match with one of the impedances that changes constantly due to the phase of LF. In this state, the matching device 88 cannot achieve matching in other phases besides the matched timing, so the reflected wave power of the IMD is larger.

[0067] Thus, in one embodiment, as shown in Figures 4(a) and 4(b), when the electrode potential is positive, the power of HF is controlled to be ON or high level, and when the electrode potential is negative, the power of HF is controlled to be OFF or low level.

[0068] In one embodiment, when the electrode potential is positive, the impedance Z is approximately constant, so it is easy to achieve matching if HF power is supplied in this timing sequence. Therefore, the HF power is controlled to be ON or at a high level in this timing sequence. On the other hand, when the electrode potential is negative, the impedance is high and varies greatly, so it is difficult to achieve matching even if HF power is supplied in this timing sequence. Therefore, the HF power supply is controlled to be OFF or at a low level in this timing sequence. This reduces the occurrence of IMD.

[0069] As shown in Figure 4(b), by controlling the HF power to a high or low level, since the HF power is not turned off when the electrode potential is negative but is kept at a low level, the reduction in plasma density can be suppressed more effectively compared to controlling the HF power to be on or off. In addition, by making the HF power applied when the electrode potential is negative smaller than the HF power applied when the electrode potential is positive, the occurrence of IMD can be suppressed.

[0070] However, the control method of making the HF power ON or High level consistent with the timing of the positive electrode potential is only one example and is not limited to this. The HF power can also be controlled to be ON or High level when at least a portion of the phase of the reference electrical state is positive. Alternatively, the HF power can be controlled to be ON or High level when at least a portion of the phase of the reference electrical state is negative. In other words, the HF power (source power) has a first state and a second state smaller than the first state; the period of the first state may also include the timing when the phase of the reference electrical state is at its peak. This peak value can be a positive peak value or a negative peak value. Furthermore, the period of the first state may also include the timing when at least a portion of the phase of the reference electrical state is positive. Furthermore, the period of the first state may also include the timing when at least a portion of the phase of the reference electrical state is negative. In addition, the power supply to the HF may be a roughly rectangular wave, including at least one of a rising wave or a falling wave, in addition to a rectangular wave whose phase is positive in accordance with the reference electrical state. Furthermore, the power supply to the HF may also be applied at least one of a timing sequence that is shifted backward or forward by a predetermined time from the timing sequence whose phase is positive in accordance with the reference electrical state.

[0071] Examples of the applicable method for controlling the timing offset of the HF power from the positive phase of the reference electrical state by a predetermined time can be listed below. If the HF power is applied only when the phase of the reference electrical state is positive, the ion energy will decrease. Depending on the type of etching, sometimes we may desire a process with higher ion energy. In this case, the HF power is applied until the reference electrical state of the LF changes from positive to negative and the desired ion energy is obtained. In this way, a process with higher ion energy can be achieved.

[0072] Alternatively, the timing of the power supply to the HF can be adjusted by shortening or lengthening the predetermined time based on the positive phase of the reference electrical state. For example, in addition to the positive phase of the reference electrical state, predetermined time can be added before and after the power supply to the HF.

[0073] Power to the HF can also be supplied during a time when the phase of the reference electrical state is negative. However, the impedance is higher during a time when the phase of the reference electrical state is negative, and it changes over time. Therefore, in this case, during a time when the phase of the reference electrical state is negative, it is advisable to control the HF power to be on (ON) in a shorter time band. For example, it is advisable to use a circuit with gate function or delay function to adjust the timing or time band of applying the HF power. It is also possible to use a circuit with an automatic adjustment function that "measures the reflection intensity in one cycle of the reference electrical state in advance, and applies the HF power during a time when the reflection of the LF power is less based on the measurement results".

[0074] For example, as shown in Figure 4(c), during the time sequence when the electrode potential is negative, the HF power can be turned ON or at a high level during a short time band, including the time when the electrode self-bias voltage Vdc is at its maximum negative value, and the HF power can be turned OFF or at a low level during other time bands. Alternatively, the reflected wave power can be detected in advance, and depending on its magnitude, the HF power can be turned OFF or at a low level during time bands with higher reflected wave power, and turned ON or at a high level during time bands with lower reflected wave power. By applying the HF power for a short time during the time band shown in Figure 4(c), including the time when the electrode potential is at its maximum negative value, stronger ion implantation can be achieved in specific etching processes such as HARC (High Aspect Ratio Contact). This allows for increased etching speed or optimized etching shape.

[0075] As explained above, according to the control method of the plasma treatment apparatus 1 in one embodiment, the on / off state or high / low level of the HF power is controlled in phase synchronization with the reference electrical state within one cycle. This reduces the occurrence of IMD. Furthermore, the ion energy and the quantity and quality of free radicals and ions can be controlled.

[0076] In addition, as illustrated in Figures 3 and 4(a) to 4(c), controlling the power of the HF to be ON or High is an example of the first state; controlling the power of the HF to be OFF or Low is an example of the second state.

[0077] In a control method for an embodiment of a plasma processing apparatus 1, a first control step is included, which alternately applies a first state and a second state in a manner synchronized with the phase of a reference electrical state within one cycle. The second state can be smaller than the first state, and the power of the second state can be 0, or a value other than 0 that is smaller than the first state.

[0078] [Example of Efficacy] Next, an example of the efficacy of controlling the ON, OFF, high, and low levels of the HF power in a manner synchronized with the phase within one cycle of the reference electrical state will be explained with reference to Figures 5 to 7. The line graph in Figure 5 is a diagram showing an example of the relationship between the phase of the LF, the plasma density Ne, and the absolute value of the self-bias voltage |Vdc| in an embodiment. Figures 6 and 7 are diagrams showing an example of the reflected wave power in an embodiment.

[0079] The line graph in Figure 5 is a measured result of applying and measuring the HF power periodically with phase changes during approximately 40% of the time band of a reference electrical state for one cycle. The vertical axis on the left side of the line graph represents the plasma density Ne (cm⁻³), and the vertical axis on the right side represents the absolute value of the self-bias voltage |Vdc| (V). When the HF power and the LF power are applied to the lower electrode of the plasma processing device 1 in an overlapping manner, the sheath of the lower electrode will change during the LF cycle. As a result, the impedance Z will change, and the plasma density Ne and the self-bias voltage Vdc will also change.

[0080] When the HF power is turned on (ON) when the electrode potential is positive and turned off (OFF) when the electrode potential is negative (refer to the upper left of Figure 5), as shown in region a of the broken line graph at the bottom of Figure 5, the plasma density Ne increases, thus improving plasma generation efficiency. Furthermore, in region a, the absolute value of the self-bias voltage |Vdc| decreases, thus effectively suppressing IMD occurrence.

[0081] Furthermore, when the HF power is turned off (OFF) during a period when the electrode potential is positive, and then turned on (ON) for a short period including the point when the electrode potential is at its maximum negative value (refer to the upper right graph of Figure 5), as shown in region b of the broken line graph at the bottom of Figure 5, the plasma density Ne is moderate to high, and the plasma generation efficiency is above moderate. This is because a large voltage is applied to the electrode when the electrode potential is negative, the sheath layer is thicker, and the electric field of the HF is weakened when the HF power is turned on (ON), thus reducing the plasma generation efficiency.

[0082] Furthermore, in region b, the absolute value of the self-bias voltage, |Vdc|, increases, thus attracting ions with monochromatic ion energy (i.e., ion energy uniformity) to wafer W. In particular, in high aspect ratio processes, monochromatic high-energy ions can be attracted to wafer W. Although the probability of IMD occurrence increases at this time, by applying HF power for a short period of time when the potential of the lower electrode is at its maximum negative value, the occurrence of IMD can still be reduced overall compared to the normal state of applying HF power.

[0083] As described above, according to an embodiment of the plasma processing apparatus 1, for example, by controlling the HF power to be ON or high level based on the positive electrode potential, the occurrence of IMD can be reduced. In addition, regarding the problem that "the sheath layer thickens during the negative electrode potential, which leads to a decrease in plasma generation efficiency", the plasma generation efficiency can be improved by applying the HF power during the positive electrode potential.

[0084] In addition, by applying HF power for a short period of time during the time when the electrode potential is most negative, monochromatic high-energy ions can be attracted to the wafer W.

[0085] For example, the upper and lower line graphs on the left side of FIG6 and the waveforms of the screens (a) and (b) on the right side of FIG6 represent an example of the detection results of the reflection detector 111 of the control unit 200 and the display results of the oscilloscope 112. The lower line graph on the left side represents Vpp and Vdc of one cycle of LF. The deeper Vdc is negative, the thicker the sheath layer, and the lower the plasma generation efficiency when HF power is applied. The upper line graph represents the traveling wave power (Pf) and reflected wave power (Pr) of HF relative to Vpp and Vdc of one cycle of LF.

[0086] An example of the waveform displayed by the oscilloscope 112 in Figure 6(a) shows the waveform A of the traveling wave power of the LF measured when the phase of the LF shown in region c is 180°, and the amplitude B of the high-frequency power on the wafer (i.e., the sum of the LF power and the HF power). The waveform of the traveling wave power of the HF is represented by C, and the waveform of the reflected wave power of the HF is represented by D. An example of the waveform displayed by the oscilloscope 112 in Figure 6(b) shows the waveform A of the traveling wave power of the LF measured when the phase of the LF shown in region d is 0° (=360°), the amplitude B of the high-frequency power on the wafer, the waveform C of the traveling wave power of the HF, and the waveform D of the reflected wave power of the HF.

[0087] It can be seen that the reflected wave power is smaller in region d compared to region c. Therefore, it can be seen that by synchronizing with "a signal that is periodically synchronized with the high frequency of the bias power in a manner that includes the phase of LF being 0°" or "the phase within one cycle of the reference electrical state measured by the bias power supply system", and by alternately applying the power of HF in a first state [e.g., ON or High level] and a second state [e.g., OFF or Low level], the occurrence of IMD can be suppressed. For example, as described above, by synchronizing the power of HF in the first state with the positive electrode potential and the power of HF in the second state with the negative electrode potential, control can be implemented according to the absolute value of the bias voltage |Vdc|, IMD can be suppressed, and plasma generation efficiency can be improved. Furthermore, by controlling the HF power to state 1 and state 2 according to the electrode potential at arbitrary intervals, high-energy ions can be attracted to the wafer W by utilizing regions with higher plasma density Ne and larger absolute values ​​of self-bias voltage |Vdc|. Additionally, by applying the HF power in a pulsed manner, the occurrence of IMD can be reduced overall.

[0088] Figure 7 shows an example of the traveling wave power (Pf) of LF Vpp, LF |Vdc|, and HF, and the reflected wave power (Pr) of HF. According to the figure, the reflected wave power (Pr) of HF varies by a maximum of about 5 times (about 10W to about 50W) during one cycle of the LF voltage. Based on the above, by controlling the power of HF in a manner synchronized with the phase of the reference electrical state during one cycle, it is possible to reduce the IMD to about 1 / 5. Furthermore, the same applies to LF Vpp and LF |Vdc|; it can be seen that by controlling the power of HF in a manner synchronized with the phase of the reference electrical state during one cycle, it can be made to vary within a range of about 1.6 times the minimum value.

[0089] [Variations] Next, control methods for variations 1 to 4 of an embodiment will be described with reference to FIGS. 8 to 11. FIG. 8 is a diagram illustrating the control method of variation 1 of an embodiment. FIG. 9 is a diagram illustrating the control method of variation 2 of an embodiment. FIG. 10 is a diagram illustrating the control method of variation 3 of an embodiment. FIG. 11 is a diagram illustrating the control method of variation 4 of an embodiment.

[0090] (Variation Example 1) In the embodiments described above, if the power of HF is pulse-modulated (refer to HF AM modulation in Figure 3) in a phase synchronization with the reference electrical state within one cycle, an HF power supply that pulse-modulates at the same frequency as LF is required, which may increase the cost.

[0091] Therefore, in the plasma processing apparatus 1 of Variation 1, as shown in FIG8(a), an additional circuit 250 constituting a branch circuit is installed on the power supply line or lower electrode connected to the first high-frequency power supply 48 and the second high-frequency power supply 90. The coil 252 and the variable capacitor 251 of the additional circuit 250 are connected in series with the power supply rod connected to the lower electrode, and the variable capacitor 251 is connected to the processing container 10 and grounded.

[0092] By using the additional circuit 250, the impedance on the processing container 10 side appears to be larger relative to the load impedance on the plasma side. Therefore, compared to the state without the additional circuit 250, even if the impedance changes, the additional circuit 250 can mitigate large changes in the impedance Z, which includes both the additional circuit 250 and the impedance on the processing container 10 side. For example, as shown in FIG8(b), by using the additional circuit 250, the change in the total impedance Z is reduced. Therefore, when HF power is applied in a phase-synchronized manner with the reference electrical state within one cycle, the occurrence of IMD can be further suppressed. Furthermore, by simply installing the additional circuit 250, an IMD suppression mechanism can be easily and inexpensively constructed. Additionally, if the additional circuit 250 is inserted into the second high-frequency power supply 90 side after the branch of the power supply bar, the HF power is less susceptible to the influence of the LF power, which is a preferred configuration. If a filter is placed between the first high-frequency power supply 48 and the second high-frequency power supply 90, the HF power will be less affected by the LF power, which can reduce the variation in the total impedance Z and thus further suppress the occurrence of IMD. The additional circuit 250 may also have at least one of the following components: a coil, a capacitor, or a diode.

[0093] (Variation Example 2) In the plasma processing apparatus 1 of Variation Example 2, as shown in FIG9(a), an impedance changing circuit 300 is installed on the power supply line or lower electrode connected to the first high-frequency power supply 48 and the second high-frequency power supply 90. The impedance changing circuit 300 functions to change the impedance in a way that the combined impedance of the load impedance on the plasma side and the impedance of the impedance changing circuit 300 is fixed. Alternatively, the impedance changing circuit 300 changes the impedance according to the phase of the LF in a way that suppresses the impedance change observed from the matching device 88. In this way, the reflected wave power can be suppressed, thereby reducing the occurrence of IMD. The impedance changing circuit 300 changes the impedance within one cycle of the reference electrical state according to the phase (or impedance) of the LF, the Vdc of the LF, or the reflected wave power, thereby suppressing IMD.

[0094] We can cite a structure in which "capacitors are arranged in an array and the capacitor connections are switched by an electronic switch" as an example of an impedance changing circuit 300. The control unit 200 controls the electronic switch to change the impedance of the impedance changing circuit 300.

[0095] The control unit 200, for example, as shown in FIG9(b), switches the connection of the capacitor of the impedance changing circuit 300 in a manner that reduces the change in the total impedance Z of the load impedance on the plasma side and the impedance of the impedance changing circuit 300. In this way, when HF power is applied in a manner that is phase-synchronized with the reference electrical state within one cycle, good impedance matching can be achieved, and the occurrence of IMD can be further suppressed.

[0096] The impedance changing circuit 300 can also be inserted into the matching circuit 88, forming an integral part of the matching circuit 88. If the impedance changing circuit 300 is inserted into the second high-frequency power supply 90 side after the branch of the power supply bar, the HF power is less susceptible to the influence of the LF power, which is a preferred configuration. If a filter is placed between the first high-frequency power supply 48 and the second high-frequency power supply 90, the HF power is even less susceptible to the influence of the LF power, reducing the variation in the total impedance Z and further suppressing the occurrence of IMD.

[0097] (Variation 3) In Variation 3, as shown in FIG10(a), an electromagnet 350 is provided on the upper part of the processing container 10. The position of the electromagnet 350 is not limited to the position shown in FIG10(a), and can be any part of the processing container 10, for example, it can be inside the processing container 10. The control unit 200 controls the strength of the electromagnet 350 according to the phase (or impedance) of the reference electrical state, the phase of LF, the electrode potential of the applied bias power, LF Vdc or the reflected wave power of HF, etc., thereby changing the characteristics of the magnetic field. For example, as shown in FIG10(b), the magnetic field is strengthened when LF Vdc is negative when the sheath layer is thickened, and the magnetic field is weakened or eliminated when LF Vdc is positive when the sheath layer is thinned, so as to reduce the change in impedance Z. In this way, the occurrence of IMD can be further suppressed. In addition, the electromagnet 350 can be a multipole electromagnet or a fixed magnet, which is an example of a magnetic field generating unit that generates a magnetic field. The control of the electromagnet 350 shown in Variation 3 can also be used in conjunction with the control of the additional circuit 250 of Variation 1 or the impedance changing circuit 300 of Variation 2.

[0098] (Variation Example 4) If the thickness of the sheath changes, the apparent capacitance changes, and the resonant frequency of HF changes. The matching device 88 sums all the L and C components of the inductance (e.g., power supply rod) and conductivity (e.g., sheath) within the processing container 10 and resonates at the frequency of HF to achieve matching.

[0099] Therefore, when the thickness of the sheath changes, the C component changes. If the original matching device 88 fails to re-match due to the change in the C component caused by the change in the thickness of the sheath, the reflected wave power will increase. However, the matching device 88 requires about 1 second to change the variable capacitor, so sometimes it cannot correctly match the change in the thickness of the sheath.

[0100] Therefore, in variation embodiment 4, the control unit 200 causes the frequency of HF to change "the amount of change in the C component caused by the change in the sheath thickness". That is, according to the formula of supply frequency f(supply frequency) ∝ 1 / √LC, the frequency f of HF is changed according to the change in the C component of the sheath thickness.

[0101] For example, assuming the capacitance of the sheath on the electrode is C, if the capacitance C changes by a factor of 4 according to the change in the thickness of the sheath, the frequency of HF will change by approximately a factor of 2. In this way, a state that is approximately matched according to the change in the thickness of the sheath can be formed.

[0102] Furthermore, when the capacitance C changes by a factor of 10 according to the change in sheath thickness, the frequency of HF changes by approximately a factor of 3.3. This allows for a state of approximately matching based on the change in sheath thickness. That is, in Variation 4, as shown in FIG11(a), the frequency of HF changes according to the aforementioned formula for resonant frequency, in a manner matching the change in sheath thickness to the change in voltage of the corresponding LF for one cycle. This allows for a state of approximately matching based on the change in sheath thickness, thereby reducing the reflected wave power of HF and suppressing the occurrence of IMD. Additionally, in Variation 4, the second high-frequency power supply 90 uses a frequency-variable power supply that can change the frequency of HF. Furthermore, the control shown in Variation 4 can also be used in conjunction with at least one of the additional circuit 250 of Variation 1, the impedance changing circuit 300 of Variation 2, or the electromagnet 350 of Variation 3.

[0103] In addition, for all examples of the above-described embodiments and variations, the offset time or delay amplitude of the circuit with gate function or delay function can be adjusted based on any one of the root element signals or measurement signals, such as the phase of LF, electrode potential, power supply system potential, Vdc, thickness of the electrode sheath, plasma luminescence, and reflection intensity of HF power.

[0104] Alternatively, instead of controlling the timing of applying HF power in a manner synchronized with the phase of the LF voltage within one cycle, as shown in FIG11(b), a pulse-shaped power (hereinafter also referred to as "LF pulse") corresponding to the peak value of the LF voltage can be applied, and the timing of applying HF power can be controlled according to the LF pulse. That is, the LF pulse corresponding to, for example, 400kHz LF can be turned on (ON) and off (OFF) and applied, and the HF power can be controlled as a pulse (HF pulse) accordingly. Alternatively, the power of the LF pulse corresponding to the peak value of the phase of the reference electrical state can be applied, and the timing of applying HF power can be controlled according to the LF pulse.

[0105] As explained above, the intensity of the power generated by the LF varies depending on the IMD. Therefore, by selecting a timing sequence with lower reflected HF power and applying HF power during the above-described embodiments and variations of the plasma processing apparatus 1, the occurrence of IMD can be reduced. By reducing the occurrence of IMD, the stability of the process or plasma processing apparatus 1 can be improved, and even the cost of the apparatus can be reduced. Furthermore, the plasma density or self-bias voltage Vdc can be controlled.

[0106] However, when the duration of HF power application decreases, there is a risk of a decrease in the absolute amount of HF power and a reduction in plasma density Ne. Therefore, LF power and HF power can be applied separately at two time points, including the points where the reference electrical state reaches its peak twice within one cycle. Furthermore, the control method for applying HF power can be freely changed. In addition, the application of HF power is not limited to the lower electrode, but can also be applied to the upper electrode.

[0107] [Control Method] As described above, a control method for an embodiment of a parallel-plate type plasma processing apparatus 1 includes: a step of supplying bias power to a lower electrode on which a wafer W is mounted; and a step of supplying a source power having a frequency higher than the bias power to the lower electrode or the upper electrode to the plasma processing space. In this control method, the source power has a first state and a second state; and further includes: a first control step, which alternately applies the first state and the second state in a manner synchronized with the phase of a synchronization signal representing a high-frequency period of bias power or within a period of a reference electrical state of any one of the voltage, current or electromagnetic field measured by the bias power supply system.

[0108] The above-described control method can also be implemented using a plasma processing apparatus other than a parallel-plate type plasma processing apparatus. The control method for a plasma processing apparatus other than a parallel-plate type plasma processing apparatus includes: a step of supplying bias power to the lower electrode; and a step of supplying source power with a frequency higher than the bias power to the plasma processing space. Similarly, in this control method, the source power has a first state and a second state, and includes a first control step of alternately applying the first state and the second state in a manner synchronized with the phase of a reference electrical state within one cycle.

[0109] [Variations 5-1 to 5-4] Next, the control method of the plasma processing apparatus 1 according to embodiments 5-1 to 5-4 will be described. In embodiments 5-1 to 5-4, control is implemented to intermittently stop the source power and / or bias power. Figures 13A to 13D are timing diagrams showing the control method of embodiments 5-1 to 5-4.

[0110] In variation 5-1 of Figure 13A, in addition to the first control step, a second control step is included, which causes the source power to stop intermittently at a period independent of the period of the reference electrical state indicated by the LF voltage. The first control step and the second control step are repeated.

[0111] In variation 5-1, the LF voltage is applied with the same period in both the first and second control steps. On the other hand, the source power is alternately repeated once or more between the first and second states in the first control step, and is intermittently stopped between the first control steps in the second control step.

[0112] In the first and second control steps, the frequency of LF can be, for example, 0.1Hz to 100Hz. In addition, the source power duty ratio [= fourth state / (third state + fourth state)] only needs to be in the range of 1% to 90%.

[0113] The state of the source power that is periodically synchronized with the reference electrical state in the first control step is an example of the third state. The state of the source power that is periodically independent of the reference electrical state in the second control step is an example of the fourth state, which is different from the third state.

[0114] The control method of Variation 5-2 of Figure 13B, in addition to the first control step which is the same as that of Variation 5-1, further includes a third control step which causes the bias power to stop intermittently at a period independent of the period of the voltage or current of HF. The state of the bias power in the third control step is an example of the fourth state.

[0115] In Variation 5-2, the first control step and the third control step are repeated. In Variation 5-2, the source power in the third control step repeats the first state and the second state with the same period as the first control step.

[0116] In addition, in the first control step, the frequency of LF can be, for example, 0.1Hz to 100Hz. Furthermore, the duty ratio of the bias power [= fourth state / (third state + fourth state)] can be within the range of 1% to 90%.

[0117] The control method of Variation 5-3 in Figure 13C, except for the first control step which is the same as that of Variation 5-1, implements the control of the source power in the second control step of Variation 5-1 and the control of the bias power in the third control step of Variation 5-2. That is, the state in Variation 5-3 where both the source power and the bias power are intermittently stopped is an example of the fourth state.

[0118] The period during which the bias power is intermittently stopped can also be synchronized with the period during which the source power is intermittently stopped. In this case, the periods during which the source power and bias power are intermittently stopped can be the same as shown in Figure 13C, or the source power can be shifted later than the bias power as shown in Figure 13D, or the source power can be shifted earlier than the bias power. The stopping time of the source power can be longer or shorter than the stopping time of the bias power.

[0119] [Effects of the Control Method in Variations 5-1 to 5-4] As explained above, in the control methods of Variations 5-1 to 5-4, the quality and quantity of free radicals and ions can be controlled. Specifically, when HF is turned off, ions in the plasma are largely eliminated, but free radicals have a longer lifetime and therefore remain for a certain period of time. Thus, for example, during the period when HF is turned off, free radicals can diffuse uniformly. In addition, during the period when HF is controlled to be off or at a low level, the ratio of ions to free radicals in the plasma can be changed. In this way, the quantity of free radicals and ions can be controlled.

[0120] Furthermore, when gas dissociation occurs, free radicals are generated accordingly. For example, C4F8 gas dissociates via C4F8→C4F7*→….→CF2, generating different free radicals (C4F7*, etc.) depending on the degree of dissociation. Ion energy or reaction time are parameters for the dissociation process. Therefore, by controlling the application sequence or time of bias power or source power to control ion energy and / or reaction time, and promoting the generation of free radicals according to a suitable program, the quality of free radicals and ions can be controlled.

[0121] Furthermore, during the period when the bias power is off, etching does not occur due to the reduced ion energy. Byproducts accumulated at the bottom of holes, etc., can be removed from the holes and deposited on the mask. Additionally, during the period when the bias power is off, free radicals can adhere to the patterned surface on the wafer W. In this way, the free radicals attached to the mask protect the mask, improving mask selectivity. This promotes etching, increases the etching rate, and results in a good etched shape.

[0122] The above is one example illustrating the effect of intermittently stopping the source power, but it is not limited to this. For example, sometimes plasma can be generated using bias power, and sometimes the same effect can be obtained by intermittently stopping the bias power. That is, by intermittently stopping the bias power, the quality and quantity of free radicals and ions can be controlled. In this way, the etching rate can be improved, and the etched shape can be improved.

[0123] In addition, in Figures 13A to 13D, in the third state, the source power is turned on (ON) when LF Vdc is deeply negative. However, it is not limited to this; the source power can also be turned on (ON) when LF Vdc is positive or in other timings. Alternatively, instead of periodically turning the source power on (ON) and off (OFF), it can be periodically controlled to a high level (High) and a low level (Low).

[0124] [Variation Example 6] Next, the control method of a variation example 6 will be described with reference to FIG14. FIG14 is a timing diagram showing the control method of a variation example 6.

[0125] For example, in the control method of Variation 6, an LF pulse as shown in FIG14 is applied to the stage 16. The positive value of the LF pulse corresponds to the positive peak value of the LF voltage; the negative value of the LF pulse corresponds to the negative peak value of the LF voltage.

[0126] In this case, in the control method of Variation 6, the first state and the second state of HF are applied alternately in a manner that synchronizes with the phase within one cycle of the LF pulse. This allows for control of the quantity and quality of free radicals and ions.

[0127] Specifically, the source power can be controlled to be off (OFF) or low level during a portion or all of the period when the LF pulse is positive, and the source power can be controlled to be on (ON) or high level during a portion or all of the period when the LF pulse is negative. In this way, the LF pulse is binary, and correspondingly, the source power is also controlled binary, thus making control easier. Furthermore, Figure 14 shows the control of the HF state shown in Figure 13A corresponding to the LF voltage pulsed in Figure 13A, but it is not limited to this. For example, the HF state shown in Figures 13B to 13D can also be controlled corresponding to the LF voltage pulsed in Figures 13B to 13D.

[0128] [Variations 7-1 to 7-4] Next, control methods according to embodiments 7-1 to 7-4 will be described with reference to FIGS. 15A to 15D. FIG. 15A is a timing diagram showing the control method of embodiment 7-1. FIG. 15B is a timing diagram showing the control method of embodiment 7-2. FIG. 15C is a timing diagram showing the control method of embodiment 7-3. FIG. 15D is a timing diagram showing the control method of embodiment 7-4.

[0129] In the control methods of Variations 7-1 and 7-2 shown in Figures 15A and 15B, in the first control step, the first state and the second state of the source power are applied alternately in phase synchronization with the phase of a reference electrical state, taking the LF voltage or electrode potential as an example. In Variation 7-1, the first state of the source power has two or more states in stages, synchronized with the negative timing of the electrode potential. In Variation 7-2, the first state of the source power smoothly has two or more states, synchronized with the negative timing of the electrode potential. However, the first state of the source power can also be synchronized with the positive timing of the electrode potential.

[0130] In the control methods of Variations 7-3 and 7-4 shown in Figures 15C and 15D, a second control step is included in addition to the first control step. In the first control step, the first state and the second state of the source power are applied alternately in phase synchronization with the phase of a reference electrical state, taking the LF voltage as an example. In Variation 7-3, the first state of the source power has two or more states in stages, synchronized with the positive timing of the electrode potential. In Variation 7-4, the first state of the source power smoothly has two or more states, synchronized with the positive timing of the electrode potential. However, the first state of the source power can also be synchronized with the negative timing of the electrode potential.

[0131] In Variations 7-1 to 7-4, by controlling the source power in the first state to a plurality of values, the quantity and quality of free radicals and ions can be controlled with greater precision. Furthermore, in addition to the first control step shown in Figures 15C and 15D, the second control step shown in Figures 15C and 15D can be replaced by the third control step shown in Figure 13B, or the second and third control steps shown in Figures 13C and 13D can be included.

[0132] In the control method of a variation embodiment 3, the strength of the electromagnet 350 is controlled according to the phase (or impedance) of the reference electrical state, the phase of the LF, the electrode potential of the applied bias power, the LF Vdc, or the reflected wave power of the HF. This reduces the impedance variation observed from the matching devices 46 and 88, thereby suppressing the occurrence of IMD. Furthermore, in the control method of a variation embodiment 4, the frequency of the HF is changed by "the amount of change in the C component caused by the change in sheath thickness". That is, according to the formula f(supply frequency) ∝ 1 / √LC, the frequency f of the HF is changed according to the change in the C component of the sheath thickness. This forms a state where a matching is approximately achieved according to the change in sheath thickness, thus reducing the reflected wave power of the HF and suppressing the occurrence of IMD. Additionally, in variation embodiment 4, the second high-frequency power supply 90 is a frequency-variable power supply that can change the frequency of the HF.

[0133] A frequency-variable power supply continuously changes its frequency when the load impedance is fixed in order to minimize the reflected power of the source power. However, when the source power is controlled in a way that is phase-synchronized with the voltage or current of the LF within one cycle, the load of the HF will periodically fluctuate significantly within one cycle of the voltage or current of the LF. Therefore, the second high-frequency power supply 90 must change its frequency in a way that corresponds to the sheath thickness (preferably the impedance corresponding to the sheath thickness) which periodically fluctuates significantly with the phase of the LF within the corresponding cycle.

[0134] For example, Figure 16 is a diagram showing an example of the reflected wave power (HF-Pr) of an embodiment. The reflected wave power of HF varies depending on the gas type or the phase of LF. For example, Figure 16(a) shows an example of the reflected wave power of HF (refer to B) when argon gas is supplied into the processing container 10, a traveling wave power of HF of 500W (HF-Pf) is applied (refer to A), and an LF power of 1000W is applied. Figure 16(b) shows an example of the reflected wave power of HF (refer to B) when SF6 gas is supplied into the processing container 10, a traveling wave power of HF of 500W (refer to A), and an LF power of 1000W is applied. In addition, C represents the potential of the wafer mounted on the stage 16. The potential of the wafer is approximately equal to the voltage Vpp of the LF at a frequency of, for example, 400 kHz, plus the amplitude of the voltage Vpp of the HF at a frequency of, for example, 100 MHz, and the wafer vibrates at these two potentials.

[0135] If we observe B in Figure 16(a) and (b), we can see that the manifestation of the reflected wave power of HF relative to the phase of LF within one cycle is different in the argon gas supply state and the SF6 gas supply state.

[0136] Since the second high-frequency power supply 90 requires time to determine the optimal frequency, it is impractical to instantly change the output wavenumber of the HF output by the second high-frequency power supply 90 to the optimal frequency according to the difference in the apparent state of the reflected HF wave power. For example, a typical variable frequency power supply can perform frequency variation and measurement of reflected wave power at a maximum of 1kHz to 10kHz. On the other hand, for example, for a 400kHz LF, dividing one cycle into 10 segments results in 4MHz. In order to shift the wavelength 10 times within the segment, the wavelength must be changed at 40MHz, and the amount of HF reflection and the direction of frequency change must be determined synchronously and instantly. This operation would be too slow with the operating frequency of a typical variable frequency power supply, making it impractical.

[0137] Therefore, in the control method of Variations 8 to 11 of the embodiment, when the reflected wave power of HF is controlled in a manner synchronized with the phase within one cycle of the reference electrical state (the phase of LF in this variation), the frequency of HF reflection with less is determined for each phase of the one-cycle of LF, and the reflected wave power of HF is suppressed to a minimum. In Variations 8 to 11, each phase of LF represents the phase when the one-cycle of LF is divided into at least 10 divisions. However, the number of divisions of the one-cycle of LF is not limited to this, and can be any one of 10 to 100 divisions. A higher number of phase divisions in the one-cycle of LF results in higher control accuracy and lower reflected wave power of HF. The control of Variations 8 to 11 is performed by the processor 100.

[0138] [Variation Example 8] First, referring to FIG17, a control method for a variation example 8 will be described. FIG17 is a timing diagram used to illustrate the control method for a variation example 8. In the control method of a variation example 8, the frequency of the HF is changed in a manner synchronized with each phase that divides one cycle of the LF into a plurality of phases. Then, the reflected wave power of the HF at this time is monitored, and based on the monitoring results, the frequency of the HF of the second high-frequency power supply 90 is controlled in a manner that reduces the reflected wave power of the HF in each phase. Then, before the program, during the program, etc., a sequence of new frequencies of the HF output by the second high-frequency power supply 90 is implemented every predetermined time, and the frequency of the HF controlled by the second high-frequency power supply 90 is determined based on the results.

[0139] The horizontal axis of Figure 17 represents time, the vertical axis on the left represents the traveling wave power (HF-Pf) and reflected wave power (HF-Pr) of HF, and the vertical axis on the right represents the wafer potential.

[0140] In the first cycle of Figure 17, the reflected wave power of HF is shown when the frequency controlled by the second high-frequency power supply 90 is set to the initial frequency during the first cycle of LF (the first cycle of C) (refer to B). The initial frequency is arbitrary, for example, set to a fundamental frequency (e.g., 40MHz).

[0141] In the second cycle of Figure 17, within the second cycle of LF (the second cycle of C), the frequency controlled by the second high-frequency power supply 90 is changed from the initial frequency to another frequency. However, in the second cycle, the frequency is not increased or decreased in each phase of the corresponding number of phase divisions in one cycle of LF, but is instead set to increase or decrease the frequency by either factor, and the phase-dependent result of the reflected amount is obtained. In the example of the second cycle in Figure 17, an example of increasing the frequency (second cycle frequency) is shown, but it could also decrease.

[0142] As a result, it can be seen that the power of the second reflected wave of HF, shown by the solid line B in Figure 17, compared with the power of the first reflected wave of HF, shown by the dashed line B, has both decreased and increased reflection depending on the phase. In Figure 17, there is a time band where "the power of the reflected wave of HF decreases when LF is in a positive phase and increases when LF is in a negative phase." However, the reflected wave power at this time is only an example and is not limited to this.

[0143] In the third cycle of Figure 17, the direction and amount of frequency variation controlled by the second high-frequency power supply 90 within the third cycle of LF are determined based on the increase or decrease of the reflected wave power of HF in each phase of the previous cycle. The third frequency shown in Figure 17 is an example of the determined direction and amount of variation. Furthermore, the reflected wave power at this time is merely an example and is not limited to this.

[0144] The amount of frequency variation and the initial direction of variation (the direction of the arrow for the third frequency) controlled by the second high-frequency power supply 90 can also be determined based on past data. Alternatively, the amount of frequency variation and the initial direction of variation controlled based on past data can be preset in the formula, and control can be performed according to the formula. Past data can be the reflected wave power of the previous HF, the reflected wave power of the HF two years prior, or the reflected wave power of the previous and previous HF. For example, based on the state of the previous reflected wave power, the direction and amount of frequency variation for each phase of the next LF cycle can be determined by reducing the reflected wave power of HF in each phase of each phase divided into one cycle. Alternatively, in addition to (or replacing) the state of the previous reflected wave power, the direction and amount of variation can be determined based on the state of the reflected wave power prior to the previous one.

[0145] The frequency controlled by the second high-frequency power supply 90 in the third time changes in the direction of reducing reflection. In the control timing at this time, for example, when one cycle of LF is divided into 10, the frequency is changed by the time interval of dividing one cycle of LF into 10.

[0146] After the fourth time, the second high-frequency power supply 90, based on the data from the third time or data obtained prior to that, causes the HF to oscillate at the optimal frequency. The frequency controlled by the second high-frequency power supply 90, by repeating a predetermined number of times within the permissible frequency range, or repeating until the reflected wave power of the HF reaches a predetermined amount, can limit the frequency with lower reflected wave power of the HF to each phase of one cycle of the LF.

[0147] In the control method of Embodiment 8, the sequence described above is executed at a specified timing. This minimizes the reflected power of the HF, which varies due to the phase of the LF or the type of gas. Furthermore, the specified timing can be exemplified by, for example, the synchronization pulse period when one cycle of the LF is divided into n (n≧10) time intervals, the time specified in the formula, a predetermined time interval, etc.

[0148] [Variation Example 9] Next, referring to FIG18, a control method for a variation example 9 will be described. FIG18 is a timing diagram used to illustrate the control method for a variation example 9. In the control method of a variation example 9, similar to variation example 8, the second high-frequency power supply 90 controls the frequency of the HF in a manner synchronized with each phase within one cycle of the LF. Furthermore, the second high-frequency power supply 90 also controls the value of the output source power.

[0149] For example, as shown in FIG18, in the time band near B1 where the reflected HF power is relatively small (as shown in FIG17), the second high-frequency power supply 90 controls the frequency of the HF and increases the output of the HF power (source power) as shown in FIG1. ​​Conversely, in the time band of B2 where the reflected HF power is relatively large, the second high-frequency power supply 90 changes the frequency of the HF and decreases the output of the source power as shown in FIG2.

[0150] In the control method of Embodiment 9, which is a variation of the embodiment, the reflected power of HF, which varies due to the phase of LF or the type of gas, can be minimized as much as possible. Furthermore, by increasing the source power when the reflected power of HF is low, the reduction in plasma density can be suppressed. Alternatively, if LF is in a positive phase, the source power can be controlled within the range of the first source power to the second source power; if LF is in a negative phase, the source power can be controlled within the range of the third source power to the fourth source power. The ranges of the first source power to the second source power and the ranges of the third source power to the fourth source power can be different ranges, the same ranges, or one range can be included by the other range, or they can partially overlap.

[0151] [Variation Example 10] Next, referring to FIG19, a control method for a variation example 10 will be described. FIG19 is a timing diagram used to illustrate the control method for a variation example 10.

[0152] The horizontal axis of Figure 19 shows an example of one cycle of the LF and one cycle of the RF pulse. The cycle of the RF pulse can be 0.1 to 100 kHz, or longer or shorter, but is set to a time band longer than the cycle of the LF. In a variation of the control method of embodiment 10, the second high-frequency power supply 90 can, for example, control the frequency of the HF by dividing the phase of one cycle of the RF pulse into a plurality of phases in a frequency-dependent manner. The frequency and source power of the HF can also be controlled by dividing the phase of one cycle of the RF pulse into a plurality of phases.

[0153] In particular, after the RF pulse is turned on (ON) and off (OFF), the plasma density Ne and electrode potential change significantly, and the reflected power of HF is prone to change differently from the normal time of the RF pulse. Therefore, as shown in Figure 19, after the moment V when the RF pulse of each cycle is turned on (ON), the rise of LF requires time, and the sheath thickness is thinner (i.e., the capacitance of the sheath is larger). Therefore, after the moment V when the RF pulse is turned on (ON), the second high-frequency power supply 90 controls the frequency of HF to be very high (refer to E).

[0154] Furthermore, in Figure 19, during the latter half of the RF pulse, the bias power is off (refer to C1). At this time, the reflected power of the HF wave is close to 0 and is fixed, as shown in B3. That is, during the timing when the bias power is off (OFF) and the source power is on (ON), the sheath impedance is often fixed because the bias power is off (OFF). Therefore, the reflected power of the HF wave is fixed. Therefore, during the period when the bias power is off (OFF), the frequency is determined in a way that minimizes the reflected power of the HF wave, and the second high-frequency power supply 90 outputs the source power at the determined frequency.

[0155] During the period when the bias power is off, the source power can be controlled to be off or on. For example, during the period when the bias power is off, as shown in C1 of Figure 19, the frequency of HF can be set to the frequency of E1 in the first half and the source power can be controlled to a high level [or on], and the frequency of HF can be changed to the frequency of E2 in the second half and the source power can be controlled to a low level [or off]. In addition, the period during which the source power and bias power stop intermittently can be the same, or the source power can be shifted later than the bias power, or the source power can be shifted earlier than the bias power. The stop time of the source power can be longer or shorter than the stop time of the bias power.

[0156] Furthermore, the control method in Variations 8 to 10 is implemented by the processor 100 of FIG2A, which sends control signals for controlling the frequency and power of the HF to the second high-frequency power supply 90 through the signal generation circuit 102. The second high-frequency power supply 90 changes the frequency or power of the output HF according to the control signals.

[0157] [Variation Example 11] Next, referring to FIG20, a control method for a variation example 11 will be described. FIG20 is a timing diagram used to illustrate the control method for a variation example 11.

[0158] As described in Variation 10, after the RF pulse is turned on (ON), the rise of LF takes time, and the sheath is relatively thin (i.e., the capacitance of the sheath is relatively large). Therefore, during the rise of the RF pulse, the plasma density Ne changes significantly, and the impedance changes considerably.

[0159] Therefore, in the control method of Variation 11, the second high-frequency power supply 90 oscillates and emits a composite wave of multiple frequencies at the rising timing of the RF pulse in one cycle of LF, that is, at E3 in FIG20. The reflection detector 111 in FIG2A detects the reflected wave power of HF relative to the multiple frequencies. The detected reflected wave power of HF at each frequency is sent to the processor 100.

[0160] For example, the second high-frequency power supply 90, when its frequency can be amplified to 35MHz to 45MHz, will oscillate and emit a composite wave at five frequencies: 41, 42, 43, 44, and 45MHz. The reflection detector 111 detects the reflected wave power relative to the source power at each of the five frequencies and sends this information to the processor 100. The processor 100 selects the frequency with the lowest reflected wave power from these signals.

[0161] For example, when the frequency with the minimum reflected wave power is 41MHz, the frequency can be determined to be 41MHz during the rise of the RF pulse in one cycle of the next LF, and this frequency can be used as the HF frequency output from the second high-frequency power supply 90. Alternatively, in E4 of Figure 20, for example, the frequency of 41MHz with the minimum reflected wave power in the previous cycle can be used as the center to output source power at five frequencies: 39, 40, 41, 42, and 43MHz.

[0162] In this way, the HF frequency output by the second high-frequency power supply 90 can reach the target frequency with the minimum HF reflected wave power as quickly as possible. As a result, the source power output by the second high-frequency power supply 90 can have a frequency with a lower HF reflected wave power more quickly, and the plasma can be ignited more quickly.

[0163] In addition, when the processor 100 implements the control method of the variation embodiment 11, it sends a control signal for controlling the frequency of HF to the second high-frequency power supply 90 through the signal generation circuit 102 based on the reflected wave power of a plurality of HF frequencies detected by the reflection detector 111 corresponding to FIG2A.

[0164] However, it is not limited to this; the second high-frequency power supply 90 may also have the functions of the processor 100 described above. In this case, the reflected wave power of the plurality of HF frequencies detected by the reflection detector 111 is directly sent from the reflection detector 111 to the second high-frequency power supply 90.

[0165] At this time, the second high-frequency power supply 90 can be implemented as a variable-frequency power supply with a control unit that performs the functions of the processor 100. That is, at this time, the control unit of the variable-frequency power supply obtains the reflected wave power of HF corresponding to the frequencies of a plurality of HF from the reflection detector 111, and selects the frequency with the minimum reflected wave power based on the obtained HF reflected wave power. Then, the control unit determines the source power of the selected frequency output from the variable-frequency power supply. The variable-frequency power supply changes to the frequency determined by the source power frequency and outputs at the predetermined power. In this way, the second high-frequency power supply 90 can control the frequency and source power of the output HF without the processor 100 and the signal generation circuit 102. In this way, the second high-frequency power supply 90 can implement the control methods of Variation 8 to Variation 11 without the processor 100.

[0166] In the control method of Variation 11, a high frequency synthesized from a plurality of frequencies is used. However, in the control methods of Variations 8 to 10, a high frequency synthesized from a plurality of frequencies may also be used. In addition, the control methods of Variations 8 to 10 may include a sequence in which the mixing ratio of the high frequency of the plurality of frequencies is freely changed to optimize it.

[0167] In the control methods of the variations 8 to 11 described above, a control method for a plasma processing apparatus having a first electrode on which a workpiece is placed is provided, characterized by including: a step of supplying bias power to the first electrode; and a step of supplying a source power having a frequency higher than the bias power to the plasma processing space; the source power having a first state and a second state; the control method further includes: a first control step, which controls the first state and the second state to a frequency of 2 or more, corresponding to dividing the phase of a periodic synchronization signal representing the high frequency of the bias power or a reference electrical state of any one of the voltage, current or electromagnetic field measured by the power supply system of the bias power into a plurality of phases.

[0168] [Variation Example 12] In Variation Example 12, the first state of the HF voltage is a pulsed voltage value that repeats two or more voltage values. In the example of FIG21, the first state of the HF voltage repeats a positive voltage value and a 0 voltage value. However, it is not limited to this, and it may also repeat three voltage values, that is, repeat two or more voltage values.

[0169] [Variation Example 13] The bias power can be a sinusoidal waveform, a pulse waveform, or a clipped waveform. That is, the bias voltage or current can be a sinusoidal waveform, an LF pulse waveform, or a clipped waveform as shown in Figure 22. The clipped waveform can modulate the bias power when HF is in the second state as shown in Figure 22, or it can modulate the bias power in the first state.

[0170] In addition, similarly, when the first state of HF takes more than two voltage values, the waveform of HF, in addition to the waveforms shown in Figures 15A to 15D and Figure 21, can also be the trimmed waveform shown in Figure 22.

[0171] The plasma processing apparatus and control method disclosed herein are all illustrative only and not limiting. The above-described embodiments can be varied and modified in various ways without exceeding the scope of the appended claims and their inventive intent. Other constructions can be adopted for the items described in the above-described embodiments, provided they do not contradict each other. Furthermore, the items described in the above-described embodiments can be combined with each other, provided they do not contradict each other.

[0172] The plasma processing apparatus disclosed in this case can also be applied to any type of capacitively coupled plasma (CCP), inductively coupled plasma (ICP), radial line slot antenna (RLSA), electron cyclotron resonance plasma (ECR), helicon wave plasma (HWP), etc.

[0173] For example, a control method for a plasma processing apparatus having a first electrode on which a subject is to be processed and a second electrode opposite to the first electrode, characterized by comprising: a step of supplying bias power to the first electrode; and a step of supplying source power having a frequency higher than the bias power to a plasma processing space; the source power having a first state and a second state; the control method may further comprise: a first control step that interactively applies the first state and the second state in a manner synchronized with the phase of the reference electrical state within one cycle.

[0174] A control method for a plasma processing apparatus having a first electrode on which a subject is disposed, characterized by comprising: a step of supplying bias power to the first electrode; and a step of supplying a source power having a frequency higher than the bias power to a plasma processing space; the source power having a first state and a second state; the control method may further comprise: a first control step that interactively applies the first state and the second state in a manner synchronized with the phase of a cycle of the reference electrical state.

[0175] The step of supplying source power with a frequency higher than the bias power to the plasma processing space can also be performed by supplying source power of a plasma generation source such as a microwave source or a high-frequency power supply to the plasma processing space.

[0176] In this specification, the wafer W is described as an example of the processed object. However, the substrate is not limited to this, and may also be various substrates used for LCD (Liquid Crystal Display), FPD (Flat Panel Display), CD substrate, printed circuit board, etc. [Simplified Explanation of the Diagram]

[0008] [Fig. 1] is a diagram showing an example of a plasma processing apparatus of an embodiment. [Fig. 2A] is a diagram showing an example of the structure of the control unit of an embodiment. [Fig. 2B] (a) to (b) are diagrams showing an embodiment controlled by a phase signal of a sensor attached to a power supply system, or controlled by a signal synchronized with the high-frequency period of the bias power. [Fig. 3] is a diagram showing an example of the supply timing of HF for the phase within one cycle of the LF of an embodiment. [Fig. 4] (a) to (c) are diagrams showing an example of the supply timing of HF for the phase within one cycle of the LF of an embodiment. [Fig. 5] is a diagram showing an example of the relationship between the phase of the LF within one cycle of an embodiment and the plasma density Ne and the self-bias voltage Vdc. [Fig. 6] is a diagram showing an example of the reflected wave power of an embodiment. [Fig. 7] is a diagram showing an example of the reflected wave power of an embodiment. [Figure 8] (a) to (b) are diagrams illustrating the control method of a variation embodiment 1. [Figure 9] (a) to (b) are diagrams illustrating the control method of a variation embodiment 2. [Figure 10] (a) to (b) are diagrams illustrating the control method of a variation embodiment 3. [Figure 11] (a) to (b) are diagrams illustrating the control method of a variation embodiment 4. [Figure 12] is a diagram showing an example of IMD (Interactive Modulation Distortion) in an embodiment. [Figure 13A] is a timing diagram showing the control method of a variation embodiment 5-1. [Figure 13B] is a timing diagram showing the control method of a variation embodiment 5-2. [Figure 13C] is a timing diagram showing the control method of a variation embodiment 5-3. [Figure 13D] is a timing diagram showing the control method of a variation embodiment 5-4. [Figure 14] is a timing diagram showing the control method of a variation embodiment 6. [Figure 15A] is a timing diagram showing the control method of a variation embodiment 7-1. [Figure 15B] is a timing diagram showing the control method of a variation embodiment 7-2. [Figure 15C] is a timing diagram showing the control method of a variation embodiment 7-3. [Figure 15D] is a timing diagram showing the control method of a variation embodiment 7-4. [Figure 16] (a) to (b) are diagrams showing an example of the reflected wave power of the source power of an embodiment. [Figure 17] is a timing diagram used to illustrate the control method of a variation embodiment 8. [Figure 18] is a timing diagram used to illustrate the control method of a variation embodiment 9. [Figure 19] is a timing diagram used to illustrate the control method of a variation embodiment 10. [Figure 20] is a timing diagram used to illustrate the control method of a variation embodiment 11.[Figure 21] is a timing diagram showing the control method of a variation of embodiment 12. [Figure 22] is a timing diagram showing the control method of a variation of embodiment 13.

Claims

1. A plasma processing apparatus, comprising: a container; a stage supporting a substrate disposed within the container; a first power source connected to the stage and applying a first waveform having a predetermined period to the stage; a second power source supplying a second waveform vibrating with a shorter period than the first waveform; and a control unit controlling the first power source and the second power source; the control unit performing the following control: (a) controlling the first power source to apply the first waveform to the stage; (b) controlling the second power source to supply the second waveform; and (c) setting a frequency, which is the reciprocal of the period of the second waveform in the first phase of the third period of the first waveform that is later than both the first and second periods, based at least on the degree of reflection of the second waveform in the first phase of the first phase of the first period of the first waveform and the degree of reflection of the second waveform in the first phase of the first phase of the second phase of the third phase of the first waveform that is later than both the first and second periods of the first waveform.

2. A plasma processing apparatus, comprising: a container; a stage supporting a substrate disposed within the container; a first power source connected to the stage and applying a first waveform having a predetermined period to the stage; a second power source supplying a second waveform oscillating with a shorter period than the first waveform; an electromagnet disposed above or inside a plasma processing space; and a control unit controlling the first power source, the second power source, and the electromagnet; the control unit performing the following controls: (a) controlling the first power source to apply the first waveform to the stage; (b) controlling the second power source to supply the second waveform; (c) detecting the degree of reflection of the second waveform in a first phase of a fourth period of the first waveform, and setting the reciprocal of the period of the second waveform in a first phase of a fifth period of the first waveform, i.e., the frequency, based on the degree of reflection; and (d) controlling the electromagnet to control the magnetic field in the plasma processing space.

3. The plasma processing apparatus as described in claim 1 or 2 further comprises: a first electrode disposed on the stage supporting the substrate; and a second electrode facing the first electrode; a first power source that applies the first waveform to the first electrode; and a second power source that supplies the second waveform to the first electrode or the second electrode.

4. The plasma processing apparatus as described in claim 1 or 2, wherein, The second power source supplies the second waveform to the mounting platform.

5. The plasma processing apparatus as claimed in claim 1 further includes an electromagnet disposed above or inside the plasma processing space; the control unit controls the electromagnet to control the magnetic field in the plasma processing space.

6. The plasma processing apparatus as described in any one of claims 1, 2, and 5, wherein, The first power supply applies the first waveform according to a frequency period corresponding to the range of 0.1kHz to 13.56MHz.

7. The plasma processing apparatus as described in any one of claims 1, 2, and 5, wherein, The frequency of the second waveform is above 13.56MHz.

8. The plasma processing apparatus as described in claim 1, wherein, The control unit performs control to change the frequency of the second waveform in each time interval that divides the third cycle into more than 10 parts.

9. The plasma processing apparatus as described in claim 1, wherein, The control unit performs control to set a predetermined frequency to the frequency of the second waveform during the first cycle.

10. The plasma processing apparatus as described in claim 1, wherein, The control unit performs control to raise or lower the frequency of the second waveform from a predetermined frequency during the second cycle.

11. The plasma processing apparatus as described in any one of claims 1, 2, 5, 8, 9, and 10, wherein, The first waveform is a pulse waveform.

12. The plasma processing apparatus as described in any one of claims 1, 2, 5, 8, 9, and 10, wherein, The first waveform is a clipped waveform.

13. The plasma processing apparatus as described in any one of claims 1, 2, 5, 8, 9, and 10, wherein, The first power supply is a bias power supply; the second power supply is a source power supply.

14. The plasma processing apparatus as described in any one of claims 1, 2, 5, 8, 9, and 10, wherein, The degree of reflection is the reflected wave power of the second waveform.

15. The plasma processing apparatus as described in any one of claims 1, 2, 5, 8, 9, and 10, wherein, After executing the control in (c), the control unit performs substrate processing.

16. The plasma processing apparatus as described in any one of claims 1, 2, 5, 8, 9, and 10, wherein, The control unit performs the control of (c) during the substrate processing.

17. The plasma processing apparatus as described in any one of claims 1, 2, 5, 8, 9, and 10, wherein, The control unit repeatedly performs the control in (c) before or during substrate processing.

18. The plasma processing apparatus as described in any one of claims 1, 2, 5, 8, 9, and 10, wherein, The control unit adjusts the frequency to reduce the degree of reflection.

19. The plasma processing apparatus as described in claim 1, wherein, The control unit sets the displacement direction of the frequency based on the degree of reflection of the second waveform in the first phase of the second cycle, so as to reduce the degree of reflection in the first phase of the third cycle.

20. The plasma processing apparatus as described in claim 1, wherein, The control unit sets the frequency displacement based on the degree of reflection of the second waveform in the first phase of the second cycle, so as to reduce the degree of reflection in the first phase of the third cycle.

21. The plasma processing apparatus as described in claim 1, wherein, The control unit further sets the frequency displacement direction based on the degree of reflection of the second waveform in the first phase of the first cycle, so as to reduce the degree of reflection in the first phase of the third cycle.

22. The plasma processing apparatus as described in claim 1, wherein, The control unit further sets a frequency shift based on the degree of reflection of the second waveform in the first phase of the first cycle, so as to reduce the degree of reflection in the first phase of the third cycle.

23. The plasma processing apparatus as described in any one of claims 1, 2, 5, 8, 9, 10, 19, 20, 21, and 22, wherein, The control unit repeatedly executes control (c) until a predetermined number of times is reached.

24. The plasma processing apparatus as described in any one of claims 1, 2, 5, 8, 9, 10, 19, 20, 21, and 22, wherein, The control unit repeatedly executes control (c) until the reflection level of the second waveform reaches a predetermined specified value.

25. The plasma processing apparatus as described in claim 1, wherein, The frequencies of each phase in the third cycle include at least phases whose frequencies are greater than those of each phase in the second cycle, and phases whose frequencies are less than those of each phase in the second cycle.

26. The plasma processing apparatus as described in claim 1, wherein, The frequency of the first phase in the third cycle becomes smaller than the frequency of the first phase in the second cycle, and the frequency of the second phase after the first phase in the third cycle becomes larger than the frequency of the second phase in the first cycle.

27. A control method for a plasma processing apparatus; the control method comprising the steps of: applying a first waveform having a predetermined period to a stage by means of a first power source; supplying a second waveform with a shorter period of vibration than the first waveform by means of a second power source; and setting a frequency, which is the reciprocal of the period of the second waveform in the first phase of the third period of the first waveform that is later than both the first and second periods of the first waveform, based at least on the degree of reflection of the second waveform in the first phase of ...

28. A control method for a plasma processing apparatus; the control method comprising the steps of: applying a first waveform having a predetermined period to a stage by means of a first power source; supplying a second waveform with a shorter period of vibration than the first waveform by means of a second power source; controlling the second power source to detect the degree of reflection of the second waveform in a first phase of a fourth period of the first waveform, and setting the reciprocal of the period of the second waveform in a first phase of a fifth period of the first waveform that is later than the fourth period, i.e., the frequency, based on the degree of reflection; and controlling an electromagnet disposed above or inside a plasma processing space to control the magnetic field in the plasma processing space.

29. The control method as described in claim 27, wherein, In each time interval of dividing the third cycle into more than 10 parts, the frequency of the second waveform is changed.

30. The control method as described in claim 27, wherein, In the first cycle, a predetermined frequency is set as the frequency of the second waveform.

31. The control method as described in any one of claims 27 to 30, wherein, The first power supply is a bias power supply; the second power supply is a source power supply.

32. The control method as described in any one of claims 27 to 30, wherein, The degree of reflection is the reflected wave power of the second waveform.

33. The control method as described in any one of claims 27 to 30, wherein, Adjust the frequency to reduce the degree of reflection.

34. The control method as described in claim 27, wherein, Based on the degree of reflection of the second waveform in the first phase of the second cycle, the displacement direction of the frequency is set to reduce the degree of reflection in the first phase of the third cycle.

35. The control method as described in claim 27, wherein, Based on the degree of reflection of the second waveform in the first phase of the second cycle, the frequency shift is set to reduce the degree of reflection in the first phase of the third cycle.

36. A computer program for causing a computer to execute a process for a plasma processing apparatus, and stored in a computer-readable recording medium; the process comprises: applying a first waveform having a predetermined period to a stage by means of a first power source; supplying a second waveform with a shorter period of vibration than the first waveform by means of a second power source; and controlling the second power source to set a frequency, which is the reciprocal of the period of the second waveform in the first phase of the third period of the first waveform that is later than the first period and the second period, based at least on the degree of reflection of the second waveform in the first phase of the first period of the first waveform and the degree of reflection of the second waveform in the first phase of the second period of the first waveform that is later than the first period and the second period.

37. A computer program for causing a computer to execute a process for a plasma processing apparatus, and stored in a computer-readable recording medium; the plasma processing apparatus includes an electromagnet disposed above or inside a plasma processing space; the process comprises: applying a first waveform having a predetermined period to a stage by means of a first power source; supplying a second waveform with a shorter period of vibration than the first waveform by means of a second power source; controlling the second power source to detect the degree of reflection of the second waveform in the first phase of the fourth period of the first waveform, and setting the reciprocal of the period of the second waveform, i.e., the frequency, in the first phase of the fifth period of the first waveform, which is later than the fourth period, according to the degree of reflection; and controlling the electromagnet to control the magnetic field in the plasma processing space.

38. A power supply system for a plasma processing apparatus, comprising: a first power supply for generating a first waveform having a predetermined period; and a second power supply for generating a second waveform that oscillates with a shorter period than the first waveform, and being controlled to set a frequency that is the reciprocal of the period of the second waveform in the first phase of the first phase of the first period of the first waveform, based at least on the degree of reflection of the second waveform in the first phase of the first phase of the second phase of the first waveform, which is later than the first period of the first waveform and the second phase of the first waveform.

39. The power supply system as described in claim 38, wherein, The second power supply is controlled to change the frequency of the second waveform during each time interval that divides the third cycle into more than 10 parts.

40. The power supply system as described in claim 38 or 39, wherein, The second power supply is controlled so that, in the first cycle, a predetermined frequency is set to the frequency of the second waveform.

41. The power supply system as described in claim 38 or 39, wherein, The first power supply is a bias power supply; the second power supply is a source power supply.

42. The power supply system as described in claim 38 or 39, wherein, The degree of reflection is the reflected wave power of the second waveform.

43. The power supply system as described in claim 38 or 39, wherein, The second power supply is controlled to adjust the frequency in order to reduce the degree of reflection.

44. The power supply system as described in claim 38 or 39, wherein, The second power supply is controlled to set the displacement direction of the frequency according to the degree of reflection of the second waveform in the first phase of the second cycle, so as to reduce the degree of reflection in the first phase of the third cycle.

45. The power supply system as described in claim 38 or 39, wherein, The second power supply is controlled to set the frequency shift based on the degree of reflection of the second waveform in the first phase of the second cycle, so as to reduce the degree of reflection in the first phase of the third cycle.

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