Plasma processing apparatus and plasma processing method

Abstract

To provide a technique capable of adjusting the thickness of the sheath on an edge ring and adjusting the distribution of plasma density in the radial direction.SOLUTION: A plasma processing apparatus disclosed herein includes a chamber, a substrate support, a high frequency power supply, and a bias power supply. The high frequency power supply supplies high frequency power to a high frequency electrode. The bias power supply provides an electrical bias to the bias electrode. An edge ring mounted on the substrate support is subject to some or another electrical bias. The outer ring extends radially outward with respect to the edge ring and receives some of the high frequency power. The power level of the high frequency power is changed in synchronization with the electrical bias within each cycle of the electrical bias.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Exemplary embodiments of the present disclosure relate to a plasma processing apparatus and a plasma processing method.

Background Art

[0002] A plasma processing apparatus is used for plasma processing of a substrate. The plasma processing apparatus includes a chamber, an electrostatic chuck, and a lower electrode. The electrostatic chuck and the lower electrode are provided in the chamber. The electrostatic chuck is provided on the lower electrode. The electrostatic chuck supports an edge ring placed thereon. The edge ring may be called a focus ring. The electrostatic chuck supports a substrate disposed within a region surrounded by the edge ring. When plasma processing is performed in the plasma processing apparatus, gas is supplied into the chamber. Also, high-frequency power is supplied to the lower electrode. Plasma is formed from the gas in the chamber. The substrate is processed by chemical species such as ions and radicals from the plasma.

[0003] When plasma processing is executed, the edge ring is consumed and the thickness of the edge ring becomes smaller. When the thickness of the edge ring becomes smaller, the position of the upper end of the plasma sheath (hereinafter referred to as "sheath") above the edge ring becomes lower. The position of the upper end of the sheath in the vertical direction above the edge ring and the position of the upper end of the sheath in the vertical direction above the substrate should be equal. Japanese Patent Application Laid-Open No. 2008-227063 (hereinafter referred to as "Patent Document 1") discloses a plasma processing apparatus capable of adjusting the position of the upper end of the sheath in the vertical direction above the edge ring. The plasma processing apparatus described in Patent Document 1 is configured to apply a DC voltage to the edge ring. Further, the plasma processing apparatus described in Patent Document 1 is configured to adjust the power level of the high-frequency power supplied to the lower electrode when a DC voltage is applied to the edge ring.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present disclosure provides a technique that enables adjustment of the thickness of a sheath on an edge ring and adjustment of the distribution of plasma density in the radial direction.

Means for Solving the Problems

[0006] In one exemplary embodiment, a plasma processing apparatus is provided. The plasma processing apparatus includes a chamber, a substrate support, a high-frequency power source, and a bias power source. The substrate support has a bias electrode. The high-frequency power source is configured to generate high-frequency power supplied to a high-frequency electrode to generate plasma above a substrate supported by the substrate support in the chamber. The bias power source is connected to the bias electrode via an electrical path. An edge ring is mounted on the substrate support. The edge ring is electrically connected to the bias power source via an impedance adjuster that provides a variable impedance between the bias electrode and the edge ring or between the electrical path and the edge ring, or is electrically connected to another bias power source. An outer ring extends radially outward with respect to the edge ring. The outer ring is electrically connected to the high-frequency power source so as to receive a part of the high-frequency power. The high-frequency power source is configured to change the power level of the high-frequency power in synchronization with the electrical bias within each period of the electrical bias output from the bias power source to the bias electrode.

Advantages of the Invention

[0007] According to one exemplary embodiment, it is possible to adjust the thickness of the sheath on the edge ring and adjust the distribution of plasma density in the radial direction.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 7

Figure 8

Mode for Carrying Out the Invention

[0009] Hereinafter, various exemplary embodiments will be described.

[0010] In one exemplary embodiment, a plasma processing apparatus is provided. The plasma processing apparatus includes a chamber, a substrate support, a high-frequency power supply, and a bias power supply. The substrate support has a bias electrode. The high-frequency power supply is configured to generate high-frequency power supplied to a high-frequency electrode to generate plasma above a substrate supported by the substrate support within the chamber. The bias power supply is connected to the bias electrode via an electrical path. An edge ring is mounted on the substrate support. The edge ring is electrically connected to the bias power supply via an impedance adjuster that provides a variable impedance between the bias electrode and the edge ring or between the electrical path and the edge ring, or is electrically connected to another bias power supply. An outer ring extends radially outward of the edge ring. The outer ring is electrically connected to the high-frequency power supply to receive a portion of the high-frequency power. The high-frequency power supply is configured to change the power level of the high-frequency power in synchronization with the electrical bias within each cycle of the electrical bias output from the bias power supply to the bias electrode.

[0011] According to the above embodiment, the level of the negative bias in the edge ring is adjusted by the impedance adjuster or another bias power supply. Therefore, according to the above embodiment, it is possible to adjust the thickness of the sheath on the edge ring. Also, in the above embodiment, the power level of the high-frequency power supplied to the outer ring is changed within each cycle of the electrical bias. Therefore, according to the above embodiment, it is possible to adjust the distribution of the plasma density in the radial direction within each cycle of the electrical bias.

[0012] In one exemplary embodiment, the plasma processing apparatus may further include a first electrode and a second electrode. The first electrode is electrically coupled to the edge ring. The first electrode may be capacitively coupled to the edge ring. The second electrode is electrically coupled to the outer ring. The second electrode may be capacitively coupled to the outer ring. The impedance adjuster provides a variable impedance between the bias electrode and the first electrode or between the electrical path and the first electrode. The outer ring receives a portion of the high-frequency power or another high-frequency power from another high-frequency power source through the second electrode.

[0013] In one exemplary embodiment, the high-frequency power source may be configured to supply a pulse of high-frequency power to the high-frequency electrode and the outer ring during the same period within each cycle of the electrical bias.

[0014] In one exemplary embodiment, the same period may be a first period in which the electrical bias has a voltage equal to or higher than the average voltage of the electrical bias within the cycle or a second period in which the electrical bias has a voltage lower than the average voltage within the cycle. When the pulse of high-frequency power is supplied to the high-frequency electrode and the outer ring during the first period, the density of the plasma on the substrate and the density of the plasma around the outer ring can be increased. Also, when the pulse of high-frequency power is supplied to the high-frequency electrode and the outer ring during the second period, the density of the plasma around the outer ring can be increased relative to the density of the plasma on the substrate.

[0015] In one exemplary embodiment, the substrate support may include a base and an electrostatic chuck provided on the base.

[0016] In one exemplary embodiment, the base may provide a lower electrode that is a bias electrode. The lower electrode may be a high-frequency electrode. The high-frequency power source may be electrically connected to the lower electrode through the electrical path described above.

[0017] In one exemplary embodiment, the plasma processing apparatus may further include an impedance adjuster. This impedance adjuster provides a variable impedance between the above electrical path and the outer ring or between the lower electrode and the outer ring.

[0018] In one exemplary embodiment, the plasma processing apparatus may further include a filter connected between the impedance adjuster that provides a variable impedance between the electrical path and the outer ring or between the lower electrode and the outer ring and the second electrode. The filter may have frequency characteristics that selectively pass high-frequency power with respect to the electrical bias supplied from the bias power source to the lower electrode.

[0019] In one exemplary embodiment, the bias electrode may be provided within the electrostatic chuck. The base may provide a lower electrode that is a high-frequency electrode. The high-frequency power source may be electrically connected to the lower electrode. In one exemplary embodiment, the plasma processing apparatus may further include an impedance adjuster that provides a variable impedance between the electrical path connecting the high-frequency power source to the lower electrode and the outer ring or between the lower electrode and the outer ring.

[0020] In another exemplary embodiment, a plasma processing apparatus is provided. The plasma processing apparatus includes a chamber, a substrate support, a first high-frequency power source, a bias power source, and a second high-frequency power source. The substrate support has a bias electrode. The first high-frequency power source is configured to generate first high-frequency power supplied to a high-frequency electrode to generate plasma above a substrate supported by the substrate support within the chamber. The bias power source is connected to the bias electrode via an electrical path. The second high-frequency power source is configured to generate second high-frequency power supplied to an outer ring. The outer ring extends radially outward with respect to an edge ring mounted on the substrate support. The edge ring is electrically connected to the bias power source via an impedance adjuster that provides a variable impedance between the bias electrode and the edge ring or between the electrical path and the edge ring, or is electrically connected to another bias power source. The second high-frequency power source is configured to change the power level of the second high-frequency power in synchronization with the electrical bias within each cycle of the electrical bias output from the bias power source to the bias electrode.

[0021] According to the above embodiment, the level of the negative bias in the edge ring is adjusted by the impedance adjuster or another bias power source. Therefore, according to the above embodiment, it becomes possible to adjust the thickness of the sheath on the edge ring. Also, in the above embodiment, the power level of the second high-frequency power supplied to the outer ring is changed within each cycle of the electrical bias. Therefore, according to the above embodiment, it becomes possible to adjust the distribution of the plasma density in the radial direction within each cycle of the electrical bias.

[0022] In one exemplary embodiment, the plasma processing apparatus may further include a first electrode and a second electrode. The first electrode is electrically coupled to the edge ring. The first electrode may be capacitively coupled to the edge ring. The second electrode is electrically coupled to the outer ring. The second electrode may be capacitively coupled to the outer ring. The impedance adjuster provides a variable impedance between the bias electrode and the first electrode or between the electrical path and the first electrode. The outer ring receives a second high-frequency power via the second electrode.

[0023] In one exemplary embodiment, the substrate support may include a base and an electrostatic chuck provided on the base.

[0024] In one exemplary embodiment, the base may provide a lower electrode that is a bias electrode. The lower electrode may be a high-frequency electrode. The high-frequency power supply may be electrically connected to the lower electrode via the above electrical path.

[0025] In one exemplary embodiment, the bias electrode may be provided in the electrostatic chuck. The base may provide a lower electrode that is a high-frequency electrode. The first high-frequency power supply may be electrically connected to the lower electrode.

[0026] In one exemplary embodiment, the second high-frequency power supply may be configured to supply a pulse of the second high-frequency power to the outer ring during the same period within each cycle of the electrical bias.

[0027] In one exemplary embodiment, each cycle of the electrical bias includes a first period in which the electrical bias has a voltage equal to or higher than the average voltage of the electrical bias within the cycle or a second period in which the electrical bias has a voltage lower than the average voltage within the cycle. The same period described above may be the first period. In this embodiment, the distribution of the plasma density in the radial direction is adjusted by the ratio between the second high-frequency power supplied to the outer ring and the first high-frequency power supplied to the high-frequency electrode during the period when the sheath on the substrate is thin.

[0028] In one exemplary embodiment, the first high-frequency power source may supply a continuous wave of the first high-frequency power in both the first period and the second period, or may supply a pulse of the first high-frequency power in the second period.

[0029] In one exemplary embodiment, the first high-frequency power source may supply a pulse of the first high-frequency power in the first period.

[0030] In one exemplary embodiment, the outer ring may extend so as to surround the edge ring.

[0031] In one exemplary embodiment, the bias power source may be configured to supply high-frequency bias power to the bias electrode, or to periodically apply a pulsed voltage or a voltage having an arbitrary waveform to the lower electrode. The pulsed voltage may have a negative polarity. The pulsed voltage may be a pulsed DC voltage having a negative polarity.

[0032] In yet another exemplary embodiment, a plasma processing method is provided. The plasma processing method includes a step (a1) of supplying high-frequency power from a high-frequency power source to a high-frequency electrode to generate plasma above a substrate supported by a substrate support in a chamber of a plasma processing apparatus. The plasma processing method further includes a step (b1) of applying an electrical bias from a bias power source to a bias electrode of the substrate support. The plasma processing apparatus includes a chamber, a substrate support, a high-frequency power source, and a bias power source connected to the bias electrode via an electrical path. An edge ring is mounted on the substrate support. The edge ring is electrically connected to the bias power source via an impedance adjuster that provides a variable impedance between the bias electrode and the edge ring or between the electrical path and the edge ring, or is electrically connected to another bias power source. An outer ring extends radially outward of the edge ring. The outer ring is electrically connected to the high-frequency power source to receive a portion of the high-frequency power. In step (a1), the high-frequency power source changes the power level of the high-frequency power in synchronization with the electrical bias within each period of the electrical bias output from the bias power source to the bias electrode.

[0033] In one exemplary embodiment, in step (a1), the high-frequency power source may supply pulses of high-frequency power to the high-frequency electrode and the outer ring during the same period within each period of the electrical bias. The same period may be a first period in which the electrical bias has a voltage equal to or higher than the average voltage of the electrical bias within the period or a second period in which the electrical bias has a voltage lower than the average voltage within the period.

[0034] In yet another exemplary embodiment, a plasma processing method is provided. The plasma processing method includes a step (a2) of supplying first high-frequency power from a first high-frequency power source to a high-frequency electrode to generate plasma above a substrate supported by a substrate support in a chamber of a plasma processing apparatus. The plasma processing method further includes a step (b2) of applying an electrical bias from a bias power source to a bias electrode of the substrate support. The plasma processing method further includes a step (c2) of supplying second high-frequency power from a second high-frequency power source to an outer ring. The plasma processing apparatus includes a chamber, a substrate support, a first high-frequency power source, a bias power source connected to the bias electrode via an electrical path, and a second high-frequency power source. An edge ring is mounted on the substrate support. The edge ring is electrically connected to the bias power source via an impedance adjuster that provides a variable impedance between the bias electrode and the edge ring or between the electrical path and the edge ring, or is electrically connected to another bias power source. The outer ring extends radially outward with respect to the edge ring. In step (c2), the second high-frequency power source changes the power level of the second high-frequency power in synchronization with the electrical bias within each cycle of the electrical bias.

[0035] In one exemplary embodiment, in step (c2), the second high-frequency power source may supply a pulse of the second high-frequency power to the outer ring during the same period within each cycle of the electrical bias. Each cycle of the electrical bias may include a first period in which the electrical bias has a voltage equal to or higher than the average voltage of the electrical bias within that cycle or a second period in which the electrical bias has a voltage lower than the average voltage within that cycle. The same period may be the first period.

[0036] Hereinafter, various exemplary embodiments will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts will be denoted by the same reference numerals.

[0037] FIG. 1 is a diagram schematically showing a plasma processing apparatus according to one exemplary embodiment. The plasma processing apparatus 1 shown in FIG. 1 is a capacitively coupled plasma processing apparatus. The plasma processing apparatus 1 includes a chamber 10. The chamber 10 provides an internal space 10s therein. The central axis of the internal space 10s is an axis AX extending in the vertical direction.

[0038] In one embodiment, the chamber 10 may include a chamber body 12. The chamber body 12 has a substantially cylindrical shape. The internal space 10s is provided in the chamber body 12. The chamber body 12 is made of, for example, aluminum. The chamber body 12 is electrically grounded. A plasma-resistant film is formed on the inner wall surface of the chamber body 12, that is, the wall surface defining the internal space 10s. This film can be a ceramic film such as a film formed by anodization or a film formed of yttrium oxide.

[0039] The side wall of the chamber body 12 provides a passage 12p. The substrate W passes through the passage 12p when being transported between the internal space 10s and the outside of the chamber 10. A gate valve 12g is provided along the side wall of the chamber body 12 for opening and closing the passage 12p.

[0040] The plasma processing apparatus 1 further includes a substrate support 16. The substrate support 16 is configured to support the substrate W placed thereon in the chamber 10. The substrate W has a substantially disc shape. The substrate W is placed on the substrate support 16 such that its center is located on the axis AX. The substrate support 16 is further configured to support an edge ring ER. The edge ring ER has an annular shape. The edge ring ER may be conductive. The edge ring ER is formed of, for example, silicon or silicon carbide. The edge ring ER is placed on the substrate support 16 such that its central axis coincides with the axis AX. The substrate W is disposed on the substrate support 16 and within the region surrounded by the edge ring ER.

[0041] The substrate supporter 16 may be surrounded by an insulating portion 17. The insulating portion 17 extends circumferentially on the outer side of the substrate supporter 16 in the radial direction with respect to the axis AX. The insulating portion 17 is formed of an insulating material such as quartz. The insulating portion 17 may support the substrate supporter 16.

[0042] The substrate supporter 16 has a base 18. The substrate supporter 16 may further have an electrostatic chuck 20. The base 18 and the electrostatic chuck 20 are provided in the chamber 10. The base 18 is formed of a conductive material such as aluminum and has a substantially disc shape. The central axis of the base 18 is the axis AX.

[0043] The base 18 provides a flow path 18f therein. The flow path 18f is a flow path for a heat exchange medium. The heat exchange medium is, for example, a refrigerant. The flow path 18f is connected to a supply device 22 for the heat exchange medium. The supply device 22 is provided outside the chamber 10. The flow path 18f receives the heat exchange medium supplied from the supply device 22. The heat exchange medium supplied to the flow path 18f flows through the flow path 18f and is returned to the supply device 22.

[0044] The electrostatic chuck 20 is provided on the base 18. When the substrate W is processed in the internal space 10s, the substrate W is placed on the electrostatic chuck 20 and held by the electrostatic chuck 20.

[0045] The electrostatic chuck 20 has a main body and a chuck electrode. The main body of the electrostatic chuck 20 is formed of a dielectric such as aluminum oxide or aluminum nitride. The main body of the electrostatic chuck 20 has a substantially disc shape. The central axis of the electrostatic chuck 20 is the axis AX. The chuck electrode is provided in the main body of the electrostatic chuck 20. The chuck electrode has a film shape. The chuck electrode is electrically connected to a DC power supply via a switch. When a voltage from the DC power supply is applied to the chuck electrode, an electrostatic attraction force is generated between the electrostatic chuck 20 and the substrate W. Due to the generated electrostatic attraction force, the substrate W is attracted to the electrostatic chuck 20 and held by the electrostatic chuck 20.

[0046] The electrostatic chuck 20 includes a substrate placement area. The substrate placement area is an area having a substantially disk shape. The central axis of the substrate placement area is the axis AX. When the substrate W is being processed in the chamber 10, it is placed on the upper surface of the substrate placement area.

[0047] In one embodiment, the electrostatic chuck 20 may further include an edge ring placement area. The edge ring placement area extends circumferentially around the central axis of the electrostatic chuck 20 so as to surround the substrate placement area. An edge ring ER is placed on the upper surface of the edge ring placement area. The edge ring ER may be partially placed on the insulating portion 17.

[0048] The plasma processing apparatus 1 may provide a gas supply line 24. The gas supply line 24 supplies a heat transfer gas, such as He gas, from a gas supply mechanism, to the gap between the upper surface of the electrostatic chuck 20 and the back surface (lower surface) of the substrate W.

[0049] The plasma processing apparatus 1 further includes an upper electrode 30. The upper electrode 30 is provided above the substrate support 16. The upper electrode 30 closes the upper opening of the chamber body 12 together with the member 32. The member 32 has insulating properties. The upper electrode 30 is supported on the upper part of the chamber body 12 via the member 32.

[0050] The upper electrode 30 may include a top plate 34 and a support 36. The lower surface of the top plate 34 defines an internal space 10s. The top plate 34 provides a plurality of gas discharge holes 34a. Each of the plurality of gas discharge holes 34a penetrates the top plate 34 in its plate thickness direction (vertical direction). The top plate 34 is formed of, for example, silicon. Alternatively, the top plate 34 may have a structure in which a plasma-resistant film is provided on the surface of an aluminum member. This film may be a ceramic film such as a film formed by anodization or a film formed of yttrium oxide.

[0051] The support 36 detachably supports the top plate 34. The support 36 is formed of a conductive material such as aluminum, for example. The support 36 provides a gas diffusion chamber 36a therein. The support 36 further provides a plurality of gas holes 36b. The plurality of gas holes 36b extend downward from the gas diffusion chamber 36a and communicate with the plurality of gas discharge holes 34a, respectively. The support 36 further provides a gas introduction port 36c. The gas introduction port 36c is connected to the gas diffusion chamber 36a. A gas supply pipe 38 is connected to the gas introduction port 36c.

[0052] A gas source group 40 is connected to the gas supply pipe 38 via a valve group 41, a flow rate controller group 42, and a valve group 43. The gas source group 40, the valve group 41, the flow rate controller group 42, and the valve group 43 constitute a gas supply unit. The gas source group 40 includes a plurality of gas sources. Each of the valve group 41 and the valve group 43 includes a plurality of valves (e.g., on-off valves). The flow rate controller group 42 includes a plurality of flow rate controllers. Each of the plurality of flow rate controllers in the flow rate controller group 42 is a mass flow controller or a pressure-controlled flow rate controller. Each of the plurality of gas sources in the gas source group 40 is connected to the gas supply pipe 38 via a corresponding valve in the valve group 41, a corresponding flow rate controller in the flow rate controller group 42, and a corresponding valve in the valve group 43. The plasma processing apparatus 1 can supply gas from one or more selected gas sources in the gas source group 40 to the internal space 10s at individually adjusted flow rates.

[0053] The plasma processing apparatus 1 may further include a baffle member 48. The baffle member 48 extends between the insulating portion 17 and the side wall of the chamber body 12. The baffle member 48 can be configured, for example, by coating a member made of aluminum with a ceramic such as yttrium oxide. The baffle member 48 provides a plurality of through holes. The space above the baffle member 48 and the space below the baffle member 48 are connected via the plurality of through holes of the baffle member 48.

[0054] The plasma processing apparatus 1 may further include an exhaust device 50. The exhaust device 50 is connected to the bottom of the chamber body 12 via an exhaust pipe 52 below the baffle member 48. The exhaust device 50 has a pressure controller such as an automatic pressure control valve and a vacuum pump such as a turbo molecular pump, and can reduce the pressure in the internal space 10s.

[0055] The plasma processing apparatus 1 further includes a high-frequency power supply 61. The high-frequency power supply 61 generates high-frequency power HF that is supplied to a high-frequency electrode to generate plasma above the substrate W supported by the substrate support 16. The high-frequency power HF has a first frequency. The first frequency is a frequency within the range of 27 to 100 MHz, for example, a frequency of 40 MHz or 60 MHz. In one embodiment, the high-frequency electrode is the base 18. That is, in one embodiment, the base 18 provides a lower electrode that is a high-frequency electrode. The high-frequency power supply 61 is connected to the base 18 via a matching unit 63. The matching unit 63 has a matching circuit configured to match the impedance on the load side (the base 18 side) of the high-frequency power supply 61 with the output impedance of the high-frequency power supply 61. In one embodiment, the high-frequency power supply 61 may be connected to the base 18 via the matching unit 63 and an electrical path 71. In one embodiment, the electrical path 71 connects the bias power supply 62 to the base 18. That is, in one embodiment, the base 18 provides a lower electrode that is a bias electrode.

[0056] The bias power supply 62 is configured to apply an electrical bias EB to the bias electrode (the base 18 in the example of FIG. 1) of the substrate support 16. The electrical bias EB can be used to draw ions into the substrate W.

[0057] In one embodiment, the bias power supply 62 may generate high-frequency bias power as the electrical bias EB. The high-frequency bias power has a second frequency. The second frequency is different from the frequency of the high-frequency power HF. The second frequency may be lower than the first frequency. The second frequency is a frequency within the range of 50 kHz to 27 MHz, for example, 400 kHz. Note that when the high-frequency power supply 61 is connected to the upper electrode 30 instead of the base 18, the second frequency may be lower than, higher than, or the same as the first frequency.

[0058] The bias power supply 62 is connected to the bias electrode (the base 18 in the example of FIG. 1) via a matching unit 64 in order to supply the high-frequency bias power to the bias electrode. The matching unit 64 has a matching circuit configured to match the impedance on the load side of the bias power supply 62 with the output impedance of the bias power supply 62.

[0059] In another embodiment, the bias power supply 62 may be configured to periodically apply a voltage pulse (i.e., a pulsed voltage) or a voltage having an arbitrary waveform as the electrical bias EB to the bias electrode (the base 18 in the example of FIG. 1). The voltage pulse may have a negative polarity. The voltage pulse may be a pulse of a negative DC voltage. The voltage pulse is applied to the base 18 at a period defined by a second frequency. In this embodiment, the second frequency may be a frequency within the range of 1 kHz to 1 MHz. The pulsed voltage may change within the period during which the pulse is applied to the bias electrode.

[0060] In one embodiment, the plasma processing apparatus 1 may further include a first electrode 81. The first electrode 81 is electrically coupled to the edge ring ER. The first electrode 81 may be capacitively coupled to the edge ring ER. The first electrode 81 is disposed below the edge ring ER. In one embodiment, the first electrode 81 may be provided within the edge ring placement region of the electrostatic chuck 20. In another embodiment, the first electrode 81 may be provided within the insulating portion 17. Note that the first electrode 81 may be directly coupled to the edge ring ER. The first electrode 81 may be a single electrode and may extend circumferentially around the axis AX. Alternatively, the first electrode 81 may include a plurality of electrodes arranged along the circumferential direction around the axis AX. The plurality of electrodes constituting the first electrode 81 may be arranged at equal intervals.

[0061] In one embodiment, the plasma processing apparatus 1 may further include an impedance adjuster 83. The impedance adjuster 83 provides a variable impedance. The variable impedance of the impedance adjuster 83 can be controlled by a control unit MC described later. In one embodiment, the impedance adjuster 83 is connected between the high-frequency electrode (in the example of FIG. 1, the base 18) and the first electrode 81. In one embodiment, the impedance adjuster 83 includes one or more variable impedance elements. The one or more variable impedance elements may include a variable capacitor. In another embodiment, the impedance adjuster 83 may include a circuit configured from a parallel connection of a plurality of series circuits. Each of the plurality of series circuits may include a series connection of a fixed impedance element and a switching element. The fixed impedance element is, for example, a fixed capacitor.

[0062] In one embodiment, the plasma processing apparatus 1 may further include a second electrode 82. The second electrode 82 is electrically coupled to the outer ring OR. The second electrode 82 may be capacitively coupled to the outer ring OR. The outer ring OR has an annular shape. The outer ring OR may have conductivity. The outer ring OR is formed of, for example, silicon or silicon carbide. The outer ring OR extends outward in the radial direction with respect to the edge ring ER. The outer ring OR is arranged such that its central axis coincides with the axis AX. In one embodiment, the outer ring OR extends so as to surround the edge ring ER. The outer ring OR may be placed on the substrate support 16 or on the insulating portion 17.

[0063] As shown in FIG. 1, the second electrode 82 may be disposed below the outer ring OR. The second electrode 82 may be provided in or on the surface of the insulating portion 17. Note that the second electrode 82 may be directly coupled to the outer ring OR. The second electrode 82 may be a single electrode and may extend circumferentially around the axis AX. Alternatively, the second electrode 82 may include a plurality of electrodes arranged along the circumferential direction around the axis AX. The plurality of electrodes constituting the second electrode 82 may be arranged at equal intervals.

[0064] In the plasma processing apparatus 1, a part of the high-frequency power HF is supplied to the outer ring OR. In one embodiment, a part of the high-frequency power HF is supplied to the outer ring OR via the second electrode 82. The outer ring OR is connected to the electrical path 71 via the impedance adjuster 84. In one embodiment, the second electrode 82 is connected to the electrical path 71 via the impedance adjuster 84. That is, the impedance adjuster 84 is connected between the electrical path 71 and the second electrode 82. The impedance adjuster 84 provides a variable impedance. The variable impedance of the impedance adjuster 84 can be controlled by the control unit MC. In one embodiment, the impedance adjuster 84 includes one or more variable impedance elements. The one or more variable impedance elements may include a variable capacitance capacitor. In another embodiment, the impedance adjuster 84 may include a circuit composed of a parallel connection of a plurality of series circuits. Each of the plurality of series circuits may include a series connection of a fixed impedance element and a switching element. The fixed impedance element is, for example, a fixed capacitance capacitor.

[0065] In one embodiment, the plasma processing apparatus 1 may further include a control unit MC. The control unit MC is a computer including a processor, a storage device, an input device, a display device, etc., and controls each part of the plasma processing apparatus 1. Specifically, the control unit MC executes a control program stored in the storage device and controls each part of the plasma processing apparatus 1 based on the recipe data stored in the storage device. By the control by the control unit MC, the process specified by the recipe data is executed in the plasma processing apparatus 1.

[0066] In one embodiment, the electrical path 71 may be configured to distribute power to the base 18 uniformly in the circumferential direction with respect to the axis AX. In one embodiment, the electrical path 71 may include a plurality of branch lines respectively connected to a plurality of positions on the base 18. The plurality of positions have equal distances from the axis AX and are arranged at equal intervals in the circumferential direction with respect to the axis AX. Also, the plurality of branch lines of the electrical path 71 are arranged at equal intervals in the circumferential direction with respect to the axis AX. Also, the electrical lengths of the electrical path 71 with respect to the respective plurality of positions on the base 18 are substantially equal to each other. According to this embodiment, it becomes possible to supply power to the base 18 uniformly via the electrical path 71.

[0067] In one embodiment, the plasma processing apparatus 1 may further include an electrical path 72. The electrical path 72 is an electrical path for the power distributed between the bias electrode (the base 18 in the example of FIG. 1) and the edge ring ER (or the first electrode 81) and supplied to the first electrode 81. The electrical path 72 may include a plurality of branch lines respectively connected to a plurality of positions on the edge ring ER (or the first electrode 81). The plurality of positions have equal distances from the axis AX and are arranged at equal intervals in the circumferential direction with respect to the axis AX. Also, the plurality of branch lines of the electrical path 72 are arranged at equal intervals in the circumferential direction with respect to the axis AX. Also, the electrical lengths of the electrical path 72 with respect to the respective plurality of positions on the edge ring ER (or the first electrode 81) are substantially equal to each other. According to this embodiment, it becomes possible to supply power to the edge ring ER uniformly via the electrical path 72.

[0068] In one embodiment, the plasma processing apparatus 1 may further include an electrical path 73. The electrical path 73 is an electrical path for power distributed between the high-frequency electrode (the base 18 in the example of FIG. 1) and the outer ring OR (or the second electrode 82) and supplied to the outer ring OR. The electrical path 73 may include a plurality of branch lines respectively connected to a plurality of positions of the outer ring OR (or the second electrode 82). The plurality of positions have equal distances from the axis AX and are arranged at equal intervals in the circumferential direction with respect to the axis AX. Also, the plurality of branch lines of the electrical path 73 are arranged at equal intervals in the circumferential direction with respect to the axis AX. Also, the electrical lengths of the electrical path 73 with respect to the plurality of positions of the outer ring OR (or the second electrode 82) are substantially equal to each other. According to this embodiment, it becomes possible to supply power to the outer ring OR uniformly via the electrical path 73.

[0069] In one embodiment, the plasma processing apparatus 1 may further include a filter 74. The filter 74 is connected between the impedance adjuster 84 and the outer ring OR (or the second electrode 82). The filter 74 may have frequency characteristics that selectively pass high-frequency power HF with respect to the electrical bias EB. Alternatively, the filter 74 may have frequency characteristics that selectively pass the electrical bias EB with respect to the high-frequency power HF. Alternatively, the passband of the filter 74 may be changeable to any of the band of the high-frequency power HF, the band of the electrical bias EB, and both of their bands.

[0070] Hereinafter, with reference to FIG. 1, FIGS. 2(a), 2(b), 3(a), and 3(b) will be referred to. Each of FIGS. 2(a) and 2(b) is a timing chart of an example of high-frequency power and electrical bias used in the plasma processing apparatus shown in FIG. 1. Each of FIGS. 3(a) and 3(b) is a timing chart of another example of high-frequency power and electrical bias used in the plasma processing apparatus shown in FIG. 1. These figures show the power level of the high-frequency power HF and the voltage level of the electrical bias EB.

[0071] In FIGS. 2(a), 2(b), 3(a), and 3(b), "H" of the high-frequency power HF indicates that the power level of the high-frequency power HF is high. "L" of the high-frequency power HF indicates that the power level of the high-frequency power HF is lower than the level indicated by "H". "ON" of the high-frequency power HF indicates that the high-frequency power HF is being supplied, and "OFF" of the high-frequency power HF indicates that the supply of the high-frequency power HF has stopped, that is, the high-frequency power HF is 0 (W). Also, "ON" of the electrical bias EB indicates that a voltage pulse (for example, a pulse of a negative DC voltage) is being applied to the base 18. Also, "OFF" of the electrical bias EB indicates that the voltage pulse has stopped, that is, the voltage of the electrical bias EB is 0 (V).

[0072] The period CY of the electrical bias EB includes a first period P1 and a second period P2. The first period P1 is a period in which the electrical bias EB has a voltage equal to or higher than the average voltage of the electrical bias EB within the period CY. The first period P1 is, for example, a period in which the electrical bias EB has a positive or 0 voltage. The second period P2 is a period in which the electrical bias EB has a voltage lower than the above average voltage. The second period P2 is, for example, a period in which the electrical bias EB has a negative voltage. As shown in FIGS. 2(a) and 2(b), the electrical bias EB may be high-frequency bias power. Alternatively, as shown in FIGS. 3(a) and 3(b), the electrical bias EB may include a voltage pulse (for example, a pulse of a negative DC voltage) periodically applied to the bias electrode.

[0073] In the plasma processing apparatus 1, the high-frequency power supply 61 is configured to change the power level of the high-frequency power HF in synchronization with the electrical bias EB within each period CY of the electrical bias EB. In one embodiment, the high-frequency power supply 61 may supply pulses of the high-frequency power HF to the high-frequency electrode (the base 18 in the example of FIG. 1) and the outer ring OR during the same period within each period CY of the electrical bias EB.

[0074] In the examples shown in Fig. 2(a) and Fig. 3(a), the pulse of high-frequency power HF is supplied to the high-frequency electrode (base 18 in the example of Fig. 1) and the outer ring OR in the first period P1. In the first period P1, the thickness of the sheath (plasma sheath) on the substrate W is small, and the impedance on the substrate W is small. Therefore, in the first period P1, the high-frequency power HF coupled to the plasma through the substrate W becomes relatively larger than the high-frequency power HF coupled to the plasma around the outer ring OR. As a result, in these examples, the plasma density in the region above the center of the substrate W is relatively increased compared to the plasma density in the region above the edge of the substrate W. Therefore, according to these examples, it is possible to correct the plasma density distribution with a high plasma density in the region above the edge of the substrate W and a low plasma density in the region above the center of the substrate W to a radially uniform density distribution. Also, in these examples, it is possible to adjust the plasma density distribution in the radial direction in a space including the region outside the region above the edge ring ER.

[0075] In the examples shown in Fig. 2(b) and Fig. 3(b), the pulse of high-frequency power HF is supplied to the high-frequency electrode (base 18 in the example of Fig. 1) and the outer ring OR in the second period P2. In the second period P2, the thickness of the sheath (plasma sheath) on the substrate W is large, and the impedance on the substrate W is large. Therefore, in the second period P2, the high-frequency power HF coupled to the plasma around the outer ring OR becomes relatively larger than the high-frequency power HF coupled to the plasma through the substrate W. As a result, in these examples, the plasma density in the region above the edge of the substrate W is increased. Therefore, in these examples, it is possible to correct the plasma density distribution with a low plasma density in the region above the edge of the substrate W and a high plasma density in the region above the center of the substrate W to a radially uniform density distribution. Also, in these examples, it is possible to adjust the plasma density distribution in the radial direction in a space including the region outside the region above the edge ring ER.

[0076] In the plasma processing apparatus 1, the change in the power level of the high-frequency power HF within each cycle CY is executed by the control of the high-frequency power supply 61 by the control unit MC. In the plasma processing apparatus 1 of one embodiment, the supply timing of the pulse of the high-frequency power HF can be set by the control of the high-frequency power supply 61 by the control unit MC. Also, the distribution ratio of the high-frequency power between the high-frequency electrode (the base 18 in the example of FIG. 1) and the outer ring OR can be set by the control of the impedance of the impedance adjuster 84 by the control unit MC. Further, the distribution ratio of the electrical bias EB between the bias electrode (the base 18 in the example of FIG. 1) and the edge ring ER can be set by the control of the impedance of the impedance adjuster 83 by the control unit MC.

[0077] The control unit MC can specify the thickness of the edge ring ER from the measured value by one or more sensors or the usage time of the edge ring ER. The control unit MC can adjust the impedance of the impedance adjuster 83 so as to equalize the position in the height direction of the interface between the plasma and the sheath in the radial direction according to the specified thickness of the edge ring ER. The control unit MC may previously hold in its storage device the relationship between the thickness of the edge ring ER and the impedance of the impedance adjuster 83 in the form of a table or a function. The control unit MC may determine the impedance of the impedance adjuster 83 from the thickness of the edge ring ER using the said relationship.

[0078] The control unit MC can set the impedance of the impedance adjuster 84 so as to equalize the distribution of the plasma density in the radial direction according to the thickness of the specified edge ring ER or one or more measurement values measured by one or more sensors. The one or more sensors may include sensors that measure the distribution of the plasma density in the internal space 10s. The one or more sensors may include sensors that measure the voltage of each of the substrate W, the edge ring ER, and the outer ring OR. The one or more sensors may include sensors that measure the current flowing through each of the substrate W, the edge ring ER, and the outer ring OR. The one or more sensors may include sensors that measure the emission intensity distribution in the internal space 10s. The control unit MC may previously hold in its storage device, in the form of a table or a function, the relationship between the thickness of the specified edge ring ER or one or more measurement values measured by one or more sensors and the impedance of the impedance adjuster 84. The control unit MC may determine the impedance of the impedance adjuster 84 from the thickness of the edge ring ER or one or more measurement values measured by one or more sensors using the said relationship.

[0079] According to the plasma processing apparatus 1, the distribution ratio of the electrical bias EB between the bias electrode (the base 18 in the example of FIG. 1) and the edge ring ER is adjusted by the impedance adjuster 83. Therefore, the level of the negative bias in the edge ring ER is adjusted by the impedance adjuster 83. Thus, it becomes possible to adjust the thickness of the sheath on the edge ring ER. Further, in the plasma processing apparatus 1, the power level of the high-frequency power HF supplied to the outer ring OR is changed within each cycle CY of the electrical bias EB. Therefore, according to the plasma processing apparatus 1, it becomes possible to adjust the distribution of the plasma density in the radial direction within each cycle CY.

[0080] Also, when the pulse of the high-frequency power HF is supplied to the high-frequency electrode and the outer ring OR in the first period P1, the plasma density on the substrate W and the plasma density around the outer ring OR can be increased. Further, when the pulse of the high-frequency power HF is supplied to the high-frequency electrode and the second electrode 82 in the second period P2, the plasma density around the outer ring OR can be increased relative to the plasma density on the substrate W. Therefore, according to the plasma processing apparatus 1, it is possible to adjust the distribution of the plasma density in the radial direction within each cycle CY.

[0081] Hereinafter, a plasma processing method using the plasma processing apparatus 1 will be described. The plasma processing method includes a step (a1) and a step (b1). In the step (a1), high-frequency power HF is supplied from the high-frequency power source 61 to the high-frequency electrode (the base 18 in the example of FIG. 1) in order to generate plasma from the gas in the chamber 10. In the step (b1), an electrical bias EB is applied from the bias power source 62 to the bias electrode (the base 18 in the example of FIG. 1). In the step (a1), the high-frequency power source 61 changes the power level of the high-frequency power HF in synchronization with the electrical bias EB within each cycle CY.

[0082] In the step (a1), the high-frequency power source 61 may supply a pulse of the high-frequency power HF to the high-frequency electrode (the base 18 in FIG. 1) and the second electrode 82 during the same period within each cycle CY. The same period may be the first period P1 or the second period P2 within the cycle CY.

[0083] Hereinafter, refer to FIG. 4. FIG. 4 is a diagram schematically showing a plasma processing apparatus according to another exemplary embodiment. Hereinafter, the differences between the plasma processing apparatus 1B shown in FIG. 4 and the plasma processing apparatus 1 will be described.

[0084] The plasma processing apparatus 1B does not include an impedance adjuster 84. In addition to a high-frequency power supply 61 (first high-frequency power supply) that generates high-frequency power HF (first high-frequency power), the plasma processing apparatus 1B further includes a high-frequency power supply 91 as a second high-frequency power supply. The high-frequency power supply 91 is configured to generate high-frequency power HF2 (second high-frequency power) to be supplied to the second electrode 82. The frequency of the high-frequency power generated by the high-frequency power supply 91 may be the same as or different from the frequency of the high-frequency power HF.

[0085] The high-frequency power supply 91 is connected to the outer ring OR via a matching unit 93 and an electrical path 75. The high-frequency power supply 91 may be connected to the second electrode 82 via the matching unit 93 and the electrical path 75. The matching unit 93 has a matching circuit configured to match the impedance on the load side of the high-frequency power supply 91 with the output impedance of the high-frequency power supply 91.

[0086] In one embodiment, the electrical path 75 may include a plurality of branch lines respectively connected to a plurality of positions of the outer ring OR (or the second electrode 82). The plurality of positions have equal distances from the axis AX and are arranged at equal intervals in the circumferential direction with respect to the axis AX. Also, the plurality of branch lines of the electrical path 75 are arranged at equal intervals in the circumferential direction with respect to the axis AX. Also, the electrical lengths of the electrical path 75 with respect to the plurality of positions of the outer ring OR (or the second electrode 82) are substantially equal to each other. According to this embodiment, it becomes possible to uniformly supply power to the outer ring OR via the electrical path 75.

[0087] Hereinafter, with reference to FIG. 4, FIGS. 5(a), 5(b), 6(a), and 6(b) are referred to. Each of FIGS. 5(a) and 5(b) is a timing chart of an example of the first high-frequency power, the second high-frequency power, and the electrical bias used in the plasma processing apparatus shown in FIG. 4. Each of FIGS. 6(a) and 6(b) is a timing chart of another example of the first high-frequency power, the second high-frequency power, and the electrical bias used in the plasma processing apparatus shown in FIG. 4. FIGS. 5(a), 5(b), 6(a), and 6(b) show the power level of the high-frequency power HF (the first high-frequency power), the power level of the high-frequency power HF2 (the second high-frequency power), and the voltage level of the electrical bias EB.

[0088] In FIGS. 5(a), 5(b), 6(a), and 6(b), "H" of the high-frequency power HF indicates that the power level of the high-frequency power HF is high. "L" of the high-frequency power HF indicates that the power level of the high-frequency power HF is lower than the level indicated by "H". "ON" of the high-frequency power HF indicates that the high-frequency power HF is being supplied, and "OFF" of the high-frequency power HF indicates that the supply of the high-frequency power HF has stopped, that is, the high-frequency power HF is 0 (W). In these figures, "H" of the high-frequency power HF2 indicates that the power level of the high-frequency power HF2 is high, and "L" of the high-frequency power HF2 indicates that the power level of the high-frequency power HF2 is lower than the level indicated by "H". "ON" of the high-frequency power HF2 indicates that the high-frequency power HF2 is being supplied, and "OFF" of the high-frequency power HF2 indicates that the supply of the high-frequency power HF2 has stopped, that is, the high-frequency power HF2 is 0 (W). Also, "ON" of the electrical bias EB indicates that a voltage pulse (for example, a pulse of a negative DC voltage) is being applied to the base 18. Also, "OFF" of the electrical bias EB indicates that the voltage pulse has stopped, that is, the voltage of the electrical bias EB is 0 (V).

[0089] Similar to the electrical bias EB described above with respect to the plasma processing apparatus 1, also in the plasma processing apparatus 1B, the first period P1 is a period in which the electrical bias EB has a voltage equal to or higher than the average voltage of the electrical bias EB within the cycle CY. The first period P1 is, for example, a period in which the electrical bias EB has a positive or zero voltage. The second period P2 is a period in which the electrical bias EB has a voltage lower than the average voltage. The second period P2 is, for example, a period in which the electrical bias EB has a negative voltage. As shown in FIGS. 5(a) and 6(a), the electrical bias EB may be high-frequency bias power. Alternatively, as shown in FIGS. 5(b) and 6(b), the electrical bias EB may include pulses of a voltage (for example, pulses of a negative DC voltage) periodically applied to the base 18.

[0090] In the plasma processing apparatus 1B, the high-frequency power supply 91 is configured to change the power level of the high-frequency power HF2 in synchronization with the electrical bias EB within each cycle CY of the electrical bias EB. In one embodiment, the high-frequency power supply 91 may be configured to supply pulses of the high-frequency power HF2 to the outer ring OR during the same period within each cycle CY.

[0091] In the example shown in FIG. 5(a) and the example shown in FIG. 5(b), the pulses of the high-frequency power HF2 are supplied to the outer ring OR during the first period P1. In these examples, as shown by the solid lines in FIGS. 5(a) and 5(b), the pulses of the high-frequency power HF may be supplied to the high-frequency electrode (the base 18 in the example of FIG. 4) and the edge ring ER during the second period P2. Alternatively, in these examples, as shown by the dashed lines in FIGS. 5(a) and 5(b), a continuous wave of the high-frequency power HF may be supplied to the high-frequency electrode (the base 18 in the example of FIG. 4) and the edge ring ER during both the first period P1 and the second period P2.

[0092] In the example shown in Fig. 5(a) and the example shown in Fig. 5(b), the pulse of the high-frequency power HF2 supplied in the first period P1 increases the density of the plasma around the outer ring OR in the first period P1. Also, a relatively large portion of the high-frequency power HF supplied in the second period P2 is coupled to the plasma around the outer ring OR. As a result, in these examples, the density of the plasma in the region above the edge of the substrate W is relatively increased with respect to the density of the plasma in the region above the center of the substrate W. Therefore, according to these examples, it is possible to correct the plasma density distribution in which the plasma density is low in the region above the edge of the substrate W and high in the region above the center of the substrate W to a radially uniform density distribution. Also, in these examples, it is possible to adjust the radially plasma density distribution in a space including the region outside the region above the edge ring ER.

[0093] In the example shown in Fig. 6(a) and the example shown in Fig. 6(b), the pulse of the high-frequency power HF2 is supplied to the outer ring OR in the first period P1. In these examples, the pulse of the high-frequency power HF is supplied to the high-frequency electrode (the base 18 in the example of Fig. 4) and the edge ring ER in the first period P1. In the first period P1, the thickness of the sheath (plasma sheath) on the substrate W is small and the impedance on the substrate W is small. Therefore, a relatively large amount of the high-frequency power HF coupled to the plasma through the center of the substrate W increases. As a result, in these examples, the density of the plasma in the region above the center of the substrate W becomes high. Therefore, in these examples, it is possible to correct the plasma density distribution in which the plasma density is high in the region above the edge of the substrate W and low in the region above the center of the substrate W to a radially uniform density distribution. Also, in these examples, the radially plasma density distribution can be adjusted in a space including the region outside the region above the edge ring ER by the high-frequency power HF2 supplied in the first period P1.

[0094] In the plasma processing apparatus 1B, the supply of the high-frequency power HF within each cycle CY is executed by the control of the high-frequency power supply 61 by the control unit MC. Also, the change in the power level of the high-frequency power HF2 within each cycle CY is executed by the control of the high-frequency power supply 91 by the control unit MC. Further, in the plasma processing apparatus 1B, the distribution ratio of the electrical bias EB between the high-frequency electrode (the susceptor 18 in the example of FIG. 4) and the edge ring ER can be set by the control of the impedance of the impedance adjuster 83 by the control unit MC. The control unit MC may determine the impedance of the impedance adjuster 83 from the thickness of the edge ring ER, similarly to the control unit MC of the plasma processing apparatus 1.

[0095] In the plasma processing apparatus 1B, the control unit MC can adjust the settings of the high-frequency power supply 61 and the high-frequency power supply 91 so as to equalize the distribution of the plasma density in the radial direction according to the thickness of the specified edge ring ER or one or more measurement values measured by one or more sensors. That is, the control unit MC can adjust the supply timing and power level of the high-frequency power HF, and the supply timing and power level of the high-frequency power HF2. The one or more sensors may include sensors that measure the distribution of the plasma density in the internal space 10s. The one or more sensors may include sensors that measure the voltage of each of the substrate W, the edge ring ER, and the outer ring OR. The one or more sensors may include sensors that measure the current flowing through each of the substrate W, the edge ring ER, and the outer ring OR. The one or more sensors may include sensors that measure the emission intensity distribution in the internal space 10s. The control unit MC may previously hold in its storage device, in the form of a table or a function, the relationship between the thickness of the specified edge ring ER or one or more measurement values measured by one or more sensors and the settings of the high-frequency power supply 61 and the high-frequency power supply 91. The control unit MC may determine the settings of the high-frequency power supply 61 and the high-frequency power supply 91 from the thickness of the edge ring ER or one or more measurement values measured by one or more sensors using the said relationship.

[0096] In the examples shown in FIGS. 5(a), 5(b), 6(a), and 6(b), the power level of the high-frequency power HF2 in the second period P2 may be set to a level indicated by "L" instead of 0. In the second period P2, the density of the plasma tends to decrease relatively significantly around the outer ring OR. Therefore, by supplying the high-frequency power HF2 to the outer ring OR even in the second period P2, it becomes possible to suppress fluctuations in the distribution of the plasma density in the radial direction.

[0097] In the plasma processing apparatus 1B, the distribution ratio of the electrical bias EB between the high-frequency electrode and the edge ring ER is adjusted by the impedance adjuster 83. Therefore, the level of the negative bias in the edge ring ER is adjusted. Thus, it becomes possible to adjust the thickness of the sheath on the edge ring ER. Also, the power level of the high-frequency power HF2 supplied to the outer ring OR is changed within each cycle CY. Therefore, according to the plasma processing apparatus 1B, it becomes possible to adjust the distribution of the plasma density in the radial direction within each cycle CY. Also, in the plasma processing apparatus 1B, the distribution of the plasma density in the radial direction is adjusted within each cycle CY by the ratio of the high-frequency power HF2 supplied to the outer ring OR and the high-frequency power HF supplied to the high-frequency electrode in the first period P1 when the sheath on the substrate W is thin.

[0098] Hereinafter, a plasma processing method using the plasma processing apparatus 1B will be described. The plasma processing method includes steps (a2), (b2), and (c2). In step (a2), in order to generate plasma from the gas in the chamber 10, the high-frequency power HF is supplied from the high-frequency power source 61 to the high-frequency electrode (the base 18 in the example of FIG. 4). In step (b2), the electrical bias EB is applied from the bias power source 62 to the bias electrode (the base 18 in the example of FIG. 4). In step (c2), the high-frequency power HF2 is supplied from the high-frequency power source 91 to the outer ring OR. In step (c2), the high-frequency power source 91 changes the power level of the high-frequency power HF2 in synchronization with the electrical bias EB within each cycle CY.

[0099] In step (c2), the high-frequency power supply 61 may supply a pulse of the high-frequency power HF2 to the second electrode 82 during the same period within each cycle CY. The same period may be the first period P1 within the cycle CY.

[0100] Hereinafter, reference is made to FIG. 7. FIG. 7 is a diagram schematically showing a plasma processing apparatus according to still another exemplary embodiment. Hereinafter, differences between the plasma processing apparatus 1C shown in FIG. 7 and the plasma processing apparatus 1B will be described.

[0101] The plasma processing apparatus 1C does not include an impedance adjuster 83. In the plasma processing apparatus 1C, the bias power supply 92 is connected to the edge ring ER (or the first electrode 81) via the matching unit 94 and the electrical path 72. The bias power supply 92 is the same power supply as the bias power supply 62. The matching unit 94 includes a matching circuit for matching the impedance on the load side of the bias power supply 92 with the output impedance of the bias power supply 92.

[0102] In the plasma processing apparatus 1C, the control unit MC can specify the thickness of the edge ring ER from the measurement value by one or more sensors or the usage time of the edge ring ER. The control unit MC may set the level of the electrical bias generated by the bias power supply 92 so as to equalize the position in the height direction of the interface between the plasma and the sheath in the radial direction according to the specified thickness of the edge ring ER. The control unit MC may previously hold in its storage device the relationship between the thickness of the edge ring ER and the electrical bias generated by the bias power supply 92 in the form of a table or a function. The control unit MC may determine the level of the electrical bias generated by the bias power supply 92 from the thickness of the edge ring ER using the relationship.

[0103] Note that in the plasma processing apparatus 1C, another high-frequency power supply that generates high-frequency power may be electrically connected to the edge ring ER (or the first electrode 81) via a matching unit.

[0104] Refer to FIG. 8 below. FIG. 8 is a diagram schematically showing a plasma processing apparatus according to yet another exemplary embodiment. Hereinafter, the differences between the plasma processing apparatus 1D and the plasma processing apparatus 1C shown in FIG. 8 will be described. In the plasma processing apparatus 1D, the bias electrode 21 is provided inside the electrostatic chuck 20. The bias electrode 21 may also serve as a chuck electrode, or may be an electrode separate from the chuck electrode. In the plasma processing apparatus 1D, the bias power supply 62 is connected to the bias electrode 21 via an electrical path different from the electrical path 71.

[0105] As described above, various exemplary embodiments have been described, but the present invention is not limited to the above-described exemplary embodiments, and various additions, omissions, substitutions, and changes may be made. Also, it is possible to form other embodiments by combining elements in different embodiments.

[0106] For example, in another embodiment, the high-frequency power supply 61 may be connected to the upper electrode 30 via the matcher 63 instead of the base 18. In this case, the upper electrode 30 is used as the high-frequency electrode.

[0107] In yet another embodiment, when the high-frequency power supply 61 is connected to the base 18 via the electrical path 71, the impedance adjuster 83 may be connected between the electrical path 71 and the edge ring ER (or the first electrode 81).

[0108] In yet another embodiment, the outer ring OR may be disposed at a position higher than the position of the edge ring ER in the vertical direction. In yet another embodiment, the outer ring OR may be disposed so as to surround the upper electrode 30. In this case, the outer ring OR may be disposed inside the member 32.

[0109] In yet another embodiment, the impedance adjuster 84 may be connected between the base 18 and the outer ring OR (or the second electrode 82).

[0110] In yet another embodiment, another bias power supply may be connected to the outer ring OR (or the second electrode 82) via the electrical path 75. The another bias power supply may generate a high-frequency bias power supplied to the outer ring OR, or may periodically generate a pulsed voltage or a voltage having an arbitrary waveform applied to the outer ring OR.

[0111] Here, various exemplary embodiments included in the present disclosure are described in the following [E1] to [E25].

[0112] [E1] A chamber, A substrate support having a bias electrode, A high-frequency power supply that generates high-frequency power supplied to a high-frequency electrode to generate plasma above a substrate supported by the substrate support in the chamber, A bias power supply connected to the bias electrode via an electrical path, Comprising, An edge ring mounted on the substrate support is electrically connected to the bias power supply via an impedance adjuster that provides a variable impedance between the bias electrode and the edge ring or between the electrical path and the edge ring, or is electrically connected to another bias power supply, An outer ring extending radially outward with respect to the edge ring is electrically connected to the high-frequency power supply so as to receive a part of the high-frequency power, The high-frequency power supply is configured to change the power level of the high-frequency power in synchronization with the electrical bias within each period of the electrical bias output from the bias power supply to the bias electrode. A plasma processing apparatus.

[0113] [E2] A first electrode electrically coupled to the edge ring, A second electrode electrically coupled to the outer ring, Further comprising, The impedance adjuster provides a variable impedance between the bias electrode and the first electrode or between the electrical path and the first electrode. The outer ring receives a part of the high-frequency power or another high-frequency power from another high-frequency power source via the second electrode. The plasma processing apparatus according to E1.

[0114] [E3] The high-frequency power supply is configured to supply a pulse of the high-frequency power to the high-frequency electrode and the outer ring during the same period within each cycle of the electrical bias. The plasma processing apparatus according to E1 or E2.

[0115] [E4] The same period is a first period in which the electrical bias has a voltage equal to or higher than the average voltage of the electrical bias within the cycle or a second period in which the electrical bias has a voltage lower than the average voltage within the cycle. The plasma processing apparatus according to E3.

[0116] [E5] The substrate support has a base and an electrostatic chuck provided on the base. The base provides a lower electrode that is the bias electrode. The lower electrode is the high-frequency electrode. The high-frequency power supply is electrically connected to the lower electrode via the electrical path. The plasma processing apparatus according to any one of E1 to E4.

[0117] [E6] The plasma processing apparatus according to E5, further comprising an impedance adjuster that provides a variable impedance between the electrical path and the outer ring or between the lower electrode and the outer ring.

[0118] [E7] A filter connected between the impedance adjuster that provides a variable impedance between the electrical path and the outer ring or between the lower electrode and the outer ring, and the outer ring is further provided. The filter has a frequency characteristic of selectively passing the high-frequency power with respect to the electrical bias supplied from the bias power supply to the lower electrode. The plasma processing apparatus according to E6.

[0119] [E8] The substrate support has a base and an electrostatic chuck provided on the base. The bias electrode is provided inside the electrostatic chuck. The base provides the lower electrode which is the high-frequency electrode. The high-frequency power supply is electrically connected to the lower electrode. The plasma processing apparatus according to any one of E1 to E4.

[0120] [E9] The plasma processing apparatus according to E8, further comprising an impedance adjuster that provides a variable impedance between the electrical path connecting the high-frequency power supply to the lower electrode and the outer ring or between the lower electrode and the outer ring.

[0121] [E10] A chamber, A substrate support having a bias electrode, A first high-frequency power supply that generates a first high-frequency power supplied to a high-frequency electrode to generate plasma above a substrate supported by the substrate support in the chamber, A bias power supply connected to the bias electrode via an electrical path, A second high-frequency power supply configured to generate a second high-frequency power supplied to an outer ring, the outer ring extending radially outside with respect to an edge ring mounted on the substrate support, the second high-frequency power supply, Comprising, The edge ring is electrically connected to the bias power supply via an impedance adjuster that provides a variable impedance between the bias electrode and the edge ring or between the electrical path and the edge ring, or is electrically connected to another bias power supply. The second high-frequency power supply is configured to change the power level of the second high-frequency power in synchronization with the electrical bias within each period of the electrical bias output from the bias power supply to the bias electrode, in a plasma processing apparatus.

[0122] [E11] A first electrode electrically coupled to the edge ring, A second electrode electrically coupled to the outer ring, and further comprising: The impedance adjuster provides a variable impedance between the bias electrode and the first electrode or between the electrical path and the first electrode, The outer ring receives the second high-frequency power via the second electrode, The plasma processing apparatus according to E10.

[0123] [E12] The substrate support has a base and an electrostatic chuck provided on the base, The base provides a lower electrode that is the bias electrode, The lower electrode is the high-frequency electrode, The first high-frequency power supply is electrically connected to the lower electrode via the electrical path, The plasma processing apparatus according to E10 or E11.

[0124] [E13] The substrate support has a base and an electrostatic chuck provided on the base, The bias electrode is provided inside the electrostatic chuck, The base provides a lower electrode that is the high-frequency electrode, The first high-frequency power supply is electrically connected to the lower electrode. The plasma processing apparatus according to E10 or E11.

[0125] [E14] The plasma processing apparatus according to any one of E10 to E13, wherein the second high-frequency power supply is configured to supply a pulse of the second high-frequency power to the outer ring during the same period within each cycle of the electrical bias.

[0126] [E15] Each cycle of the electrical bias includes a first period in which the electrical bias has a voltage equal to or higher than the average voltage of the electrical bias within the cycle and a second period in which the electrical bias has a voltage lower than the average voltage within the cycle. The same period is the first period. The plasma processing apparatus according to E14.

[0127] [E16] The plasma processing apparatus according to E15, wherein the first high-frequency power supply supplies a continuous wave of the first high-frequency power in both the first period and the second period, or supplies a pulse of the first high-frequency power in the second period.

[0128] [E17] The plasma processing apparatus according to E15, wherein the first high-frequency power supply supplies a pulse of the first high-frequency power in the first period.

[0129] [E18] The plasma processing apparatus according to any one of E1 to E17, wherein the outer ring extends so as to surround the edge ring.

[0130] [E19] The plasma processing apparatus according to any one of E1 to E18, wherein the bias power supply is configured to supply high-frequency bias power to the bias electrode or to periodically apply a pulsed voltage or a voltage having an arbitrary waveform to the bias electrode.

[0131] [E20] (a1) A step of supplying high-frequency power from a high-frequency power source to a high-frequency electrode to generate plasma above a substrate supported by a substrate support in a chamber of a plasma processing apparatus; (b1) A step of applying an electrical bias from a bias power source to a bias electrode of the substrate support; comprising; the plasma processing apparatus includes; the chamber; the substrate support; the high-frequency power source; the bias power source connected to the bias electrode via an electrical path; and is provided with; an edge ring mounted on the substrate support is electrically connected to the bias power source via an impedance adjuster that provides a variable impedance between the bias electrode and the edge ring or between the electrical path and the edge ring, or is electrically connected to another bias power source; an outer ring extending radially outward with respect to the edge ring is electrically connected to the high-frequency power source so as to receive a part of the high-frequency power; in the above (a1), the high-frequency power source changes the power level of the high-frequency power in synchronization with the electrical bias within each period of the electrical bias output from the bias power source to the bias electrode; Plasma processing method.

[0132] [E21] In the above (a1), the high-frequency power source supplies pulses of the high-frequency power to the high-frequency electrode and the outer ring during the same period within each period of the electrical bias, the plasma processing method according to E20.

[0133] [E22] The same period is a first period in which the electrical bias has a voltage equal to or higher than the average voltage of the electrical bias within its period or a second period in which the electrical bias has a voltage lower than the average voltage within the period, the plasma processing method according to E21.

[0134] [E23] (a2) A step of supplying first high-frequency power from a first high-frequency power source to a high-frequency electrode to generate plasma above a substrate supported by a substrate support in a chamber of a plasma processing apparatus; (b2) A step of applying an electrical bias from a bias power source to a bias electrode of the substrate support; (c2) A step of supplying second high-frequency power from a second high-frequency power source to an outer ring; comprising; The plasma processing apparatus includes: the chamber; the substrate support; the first high-frequency power source; the bias power source connected to the bias electrode via an electrical path; the second high-frequency power source; and is provided with; An edge ring mounted on the substrate support is electrically connected to the bias power source via an impedance adjuster that provides a variable impedance between the bias electrode and the edge ring or between the electrical path and the edge ring, or is electrically connected to another bias power source; The outer ring extends radially outward with respect to the edge ring; In (c2), the second high-frequency power source changes the power level of the second high-frequency power in synchronization with the electrical bias within each cycle of the electrical bias; Plasma processing method.

[0135] [E24] In (c2), the second high-frequency power source supplies pulses of the second high-frequency power to the outer ring during the same period within each cycle of the electrical bias, the plasma processing method according to E23.

[0136] [E25] Each period of the electrical bias includes a first period in which the electrical bias has a voltage equal to or higher than the average voltage of the electrical bias within the period and a second period in which the electrical bias has a voltage lower than the average voltage within the period. The same period is the first period. The plasma processing method according to E24.

[0137] From the above description, it will be understood that the various embodiments of the present disclosure are described herein for purposes of illustration and that various changes can be made without departing from the scope and spirit of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, and the true scope and spirit are indicated by the appended claims.

Description of Reference Numerals

[0138] 1... Plasma processing apparatus, 10... Chamber, 16... Substrate support, 18... Base, 61... High-frequency power supply, 62... Bias power supply, ER... Edge ring, 81... First electrode, 83... Impedance adjuster, OR... Outer ring, 82... Second electrode.

Claims

[Claim 1] A chamber; a substrate support having a bias electrode; a radio frequency power supply that generates radio frequency power that is supplied to a radio frequency electrode to generate a plasma above a substrate supported by the substrate support within the chamber; a bias power supply connected to the bias electrode via an electrical path; Equipped with an edge ring mounted on the substrate support is electrically connected to the bias power supply via an impedance adjuster that provides a variable impedance between the bias electrode and the edge ring or between the electrical path and the edge ring, or is electrically connected to a separate bias power supply; an outer ring extending radially outwardly of the edge ring, the outer ring being electrically connected to the RF power source to receive a portion of the RF power; The high frequency power supply is configured to change the power level of the high frequency power in synchronization with the electric bias within each period of the electric bias output from the bias power supply to the bias electrode. Plasma processing equipment.

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