PLASMA PROCESSING APPARATUS

A disclosed plasma processing apparatus includes a substrate support. The substrate support has a first region configured to support a substrate and a second region configured to support an edge ring. The first electrode is provided in the first region. The second electrode is provided in the second region. The first bias power source is connected to the first electrode via the first circuit. The second bias power source is connected to the second electrode via the second circuit. The second circuit has impedance higher than impedance of the first circuit at a common bias frequency of a first electrical bias generated by the first bias power source and a second electrical bias generated by the second bias power source.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims the benefit of priority from Japanese Patent Application No. 2020-046282 filed on Mar. 17, 2020, the entire contents of which are incorporated herein by reference.

FIELD

Exemplary embodiments of the present disclosure relate to a plasma processing apparatus.

BACKGROUND

In the manufacture of electronic devices, a plasma processing apparatus is used. The plasma processing apparatus has a chamber and a substrate support. The substrate support has a lower electrode and an electrostatic chuck. The electrostatic chuck is provided on the lower electrode. The substrate support supports an edge ring. A substrate is placed in a region surrounded by the edge ring on the substrate support. Radio frequency bias power is supplied to the lower electrode in order to draw ions from plasma into the substrate. Japanese Unexamined Patent Publication No. 2019-36658 discloses such a plasma processing apparatus.

SUMMARY

In an exemplary embodiment, a plasma processing apparatus is provided. The plasma processing apparatus includes a chamber, a substrate support, a first bias power source, a second bias power source, a first circuit, and a second circuit. The substrate support has a first region, a second region, a first electrode, and a second electrode. The first region is configured to support a substrate. The second region is configured to support an edge ring. The first electrode is provided in the first region. The second electrode is provided in the second region and separated from the first electrode. The first bias power source is configured to generate a first electrical bias and electrically connected to the first electrode. The second bias power source is configured to generate a second electrical bias and electrically connected to the second electrode. The first circuit is connected between the first electrode and the first bias power source. The second circuit is connected between the second electrode and the second bias power source. The second circuit has impedance higher than impedance of the first circuit at a common bias frequency of the first electrical bias and the second electrical bias.

DETAILED DESCRIPTION

Hereinafter, various exemplary embodiments will be described.

In an exemplary embodiment, a plasma processing apparatus is provided. The plasma processing apparatus includes a chamber, a substrate support, a first bias power source, a second bias power source, a first circuit, and a second circuit. The substrate support has a first region, a second region, a first electrode, and a second electrode. The first region is configured to support a substrate. The second region is configured to support an edge ring. The first electrode is provided in the first region. The second electrode is provided in the second region and separated from the first electrode. The first bias power source is configured to generate a first electrical bias and electrically connected to the first electrode. The second bias power source is configured to generate a second electrical bias and electrically connected to the second electrode. The first circuit is connected between the first electrode and the first bias power source. The second circuit is connected between the second electrode and the second bias power source. The second circuit has impedance higher than impedance of the first circuit at a common bias frequency of the first electrical bias and the second electrical bias.

In the plasma processing apparatus of the above embodiment, the first electrode and the substrate form a first capacitor element. Further, the second electrode and the edge ring form a second capacitor element. An area of the edge ring is generally smaller than an area of the substrate. Therefore, the capacitance of the second capacitor element is lower than the capacitance of the first capacitor element. Therefore, when an electric current that is supplied to the first capacitor element and an electric current that is supplied to the second capacitor element are the same as each other, the voltage waveform of the edge ring changes at higher speed than the voltage waveform of the substrate. In the above embodiment, the first circuit is provided between the first electrode and the first bias power source, and the second circuit is provided between the second electrode and the second bias power source. At the bias frequency, the impedance of the second circuit is higher than the impedance of the first circuit. Therefore, the difference between the voltage waveform of the substrate and the voltage waveform of the edge ring is reduced.

In an exemplary embodiment, the impedance of the first circuit and the impedance of the second circuit are set such that a ratio between an electric current supplied to the substrate and an electric current supplied to the edge ring may be equal to a ratio between an area of the substrate and an area of the edge ring.

In an exemplary embodiment, the plasma processing may further include a controller. The controller may be configured to control the second bias power source to increase a setting level of the second electrical bias according to a decrease in a thickness of the edge ring and controls the second circuit to reduce the impedance of the second circuit according to the decrease in the thickness of the edge ring.

In an exemplary embodiment, each of the first electrical bias and the second electrical bias may be a pulse wave that is periodically generated at a cycle that is defined by the bias frequency. The pulse wave includes a pulse of a negative voltage. The pulse of the negative voltage may be a pulse of a negative direct-current voltage.

In an exemplary embodiment, each of the first electrical bias and the second electrical bias may be radio frequency power having the bias frequency.

In an exemplary embodiment, the first circuit may have a first resistor and a first capacitor. The first resistor is connected between the first electrode and the first bias power source. The first capacitor is connected between a node on an electrical path connecting the first resistor with the first electrode and a ground. The second circuit may have a second resistor and a second capacitor. The second resistor is connected between the second electrode and the second bias power source. The second capacitor is connected between a node on an electrical path connecting the second resistor with the second electrode and a ground. At least one of the second resistor or the second capacitor may be variable.

In an exemplary embodiment, the first circuit may have a first inductor and a first capacitor. The first inductor is connected between the first electrode and the first bias power source. The first capacitor is connected between a node on an electrical path connecting the first inductor with the first electrode and a ground. The second circuit may have a second inductor and a second capacitor. The second inductor is connected between the second electrode and the second bias power source. The second capacitor is connected between a node on an electrical path connecting the second inductor with the second electrode and a ground. At least one of the second inductor or the second capacitor may be variable.

Hereinafter, various exemplary embodiments will be described in detail with reference to the drawings. In the drawings, the same or equivalent portions are denoted by the same reference symbols.

FIG. 1schematically illustrates a plasma processing apparatus according to an exemplary embodiment. A plasma processing apparatus1shown inFIG. 1is provided with a chamber10.FIG. 2illustrates the configuration in the chamber of the plasma processing apparatus according to an exemplary embodiment. As shown in FIG.2, the plasma processing apparatus1may be a capacitively coupled plasma processing apparatus.

The chamber10provides an internal space10stherein. The central axis of the internal space10sis an axis AX which extends in the vertical direction. In an embodiment, the chamber10includes a chamber body12. The chamber body12has a substantially cylindrical shape. The internal space10sis provided in the chamber body12. The chamber body12is formed of, for example, aluminum. The chamber body12is electrically grounded. A film having plasma resistance is formed on the inner wall surface of the chamber body12, that is, the wall surface defining the internal space10s.This film may be a ceramic film such as a film formed by anodization or a film formed of yttrium oxide.

A passage12pis formed in a side wall of the chamber body12. A substrate W passes through the passage12pwhen it is transferred between the internal space10sand the outside of the chamber10. A gate valve12gis provided along the side wall of the chamber body12for opening and closing of the passage12p.

The plasma processing apparatus1is further provided with a substrate support16. The substrate support16is configured to support the substrate W placed thereon in the chamber10. The substrate W has a substantially disk shape. The substrate support16is supported by a support17. The support17extends upward from a bottom portion of the chamber body12. The support17has a substantially cylindrical shape. The support17is formed of an insulating material such as quartz.

The substrate support16has a lower electrode18and an electrostatic chuck20. The lower electrode18and the electrostatic chuck20are provided in the chamber10. The lower electrode18is formed of a conductive material such as aluminum and has a substantially disk shape.

A flow path18fis formed in the lower electrode18. The flow path18fis a flow path for a heat exchange medium. As the heat exchange medium, for example, a liquid refrigerant is used. A supply device for the heat exchange medium (for example, a chiller unit) is connected to the flow path18f.The supply device is provided outside the chamber10. The heat exchange medium is supplied from the supply device to the flow path18fthrough a pipe23a.The heat exchange medium supplied to the flow path18fis returned to the supply device through a pipe23b.

The electrostatic chuck20is provided on the lower electrode18. As shown inFIG. 1, the electrostatic chuck20has a dielectric portion20dand an electrode21a.The electrostatic chuck20may further has an electrode22aand an electrode22b.When the substrate W is processed in the internal space10s,the substrate W is placed on the electrostatic chuck20and is held by the electrostatic chuck20. Further, an edge ring ER is mounted on the substrate support16. The edge ring ER is a plate having a substantially ring shape. The edge ring ER has electrical conductivity. The edge ring ER is formed of, for example, silicon or silicon carbide. As shown inFIG. 2, the edge ring ER is mounted on the substrate support16such that the central axis thereof coincides with the axis AX. The substrate W accommodated in the chamber10is disposed on the electrostatic chuck20and in a region surrounded by the edge ring ER.

The plasma processing apparatus1may be further provided with a gas line25. The gas line25supplies a heat transfer gas, for example, a He gas, from a gas supply mechanism to a gap between the upper surface of the electrostatic chuck20(a first region to be described later) and the rear surface (lower surface) of the substrate W.

The plasma processing apparatus1may be further provided with an outer peripheral portion28and an outer peripheral portion29. The outer peripheral portion28extends upward from the bottom portion of the chamber body12. The outer peripheral portion28has a substantially cylindrical shape and extends along the outer periphery of the support17. The outer peripheral portion28is formed of a conductive material. The outer peripheral portion28is electrically grounded. A film having plasma resistance is formed on the surface of the outer peripheral portion28. This film may be a ceramic film such as a film formed by anodization or a film formed of yttrium oxide.

The outer peripheral portion29is provided on the outer peripheral portion28. The outer peripheral portion29is formed of a material having insulation properties. The outer peripheral portion29is formed of ceramic such as quartz, for example. The outer peripheral portion29has a substantially cylindrical shape. The outer peripheral portion29extends along the outer peripheries of the lower electrode18and the electrostatic chuck20.

The plasma processing apparatus1is further provided with an upper electrode30. The upper electrode30is provided above the substrate support16. The upper electrode30closes an upper opening of the chamber body12together with a member32. The member32has insulation properties. The upper electrode30is supported on an upper portion of the chamber body12through the member32.

The upper electrode30includes a ceiling plate34and a support36. The lower surface of the ceiling plate34defines the internal space10s.A plurality of gas discharge holes34aare formed in the ceiling plate34. Each of the plurality of gas discharge holes34apenetrates the ceiling plate34in a plate thickness direction (the vertical direction). The ceiling plate34is formed of, for example, silicon.

Alternatively, the ceiling plate34may have a structure in which a plasma-resistant film is provided on the surface of a member made of aluminum. This film may be a ceramic film such as a film formed by anodization or a film formed of yttrium oxide.

The support36detachably supports the ceiling plate34. The support36is formed of a conductive material such as aluminum, for example. A gas diffusion chamber36ais provided in the interior of the support36. A plurality of gas holes36bextend downward from the gas diffusion chamber36a.The plurality of gas holes36bcommunicate with the plurality of gas discharge holes34a,respectively.

A gas introduction port36cis formed in the support36. The gas introduction port36cis connected to the gas diffusion chamber36a.A gas supply pipe38is connected to the gas introduction port36c.

A gas source group40is connected to the gas supply pipe38through a valve group41, a flow rate controller group42, and a valve group43. The gas source group40, the valve group41, the flow rate controller group42, and the valve group43configure a gas supply unit. The gas source group40includes a plurality of gas sources. Each of the valve group41and the valve group43includes a plurality of valves (for example, on-off valves). The flow rate controller group42includes a plurality of flow rate controllers. Each of the plurality of flow rate controllers of the flow rate controller group42is a mass flow controller or a pressure control type flow rate controller. Each of the plurality of gas sources of the gas source group40is connected to the gas supply pipe38through a corresponding valve of the valve group41, a corresponding flow rate controller of the flow rate controller group42, and a corresponding valve of the valve group43. The plasma processing apparatus1can supply gases from one or more gas sources selected from the plurality of gas sources of the gas source group40to the internal space10sat individually adjusted flow rates.

A baffle plate48is provided between the outer peripheral portion28and the side wall of the chamber body12. The baffle plate48may be configured, for example, by coating a member made of aluminum with ceramic such as yttrium oxide. A number of through-holes are formed in the baffle plate48. An exhaust pipe52is connected to the bottom portion of the chamber body12below the baffle plate48. An exhaust device50is connected to the exhaust pipe52. The exhaust device50has 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 space10s.

Hereinafter, the substrate support16will be described in detail. As described above, the substrate support16has the lower electrode18and the electrostatic chuck20. As shown inFIG. 1, the plasma processing apparatus1has a radio frequency power source57. The radio frequency power source57is connected to the lower electrode18through a matcher58. The radio frequency power source57is a power source that generates radio frequency power for plasma generation. The radio frequency power generated by the radio frequency power source57has a frequency within the range of 27 to 100 MHz, for example, a frequency of 40 MHz or 60 MHz. The matcher58has a matching circuit for matching the impedance on the load side (the lower electrode18side) of the radio frequency power source57with the output impedance of the radio frequency power source57. The radio frequency power source57may not be electrically connected to the lower electrode18, and may be connected to the upper electrode30through the matcher58.

In the plasma processing apparatus1, a radio frequency electric field is generated in the chamber10by the radio frequency power from the radio frequency power source57. The gas in the chamber10is excited by the generated radio frequency electric field. As a result, plasma is generated in the chamber10. The substrate W is processed with chemical species such as ions and/or radicals from the generated plasma.

The substrate support16has a first region21and a second region22. The first region21is a central region of the substrate support16. The first region21includes the central region of the electrostatic chuck20and the central region of the lower electrode18. The second region22extends in a circumferential direction on the outside in a radial direction with respect to the first region21. The second region22includes a peripheral edge region of the electrostatic chuck20and a peripheral edge region of the lower electrode18. In the plasma processing apparatus1, the first region21and the second region22are configured from a single electrostatic chuck and are integrated with each other. InFIG. 1, the boundary between the first region21and the second region22is indicated by a broken line. In another embodiment, the first region21and the second region22may be configured from individual electrostatic chucks.

The first region21is configured to support the substrate W placed thereon (that is, on the upper surface thereof). The first region21is a region having a disk shape. The central axis of the first region21substantially coincides with the axis AX. The first region21shares the dielectric portion20dwith the second region22. The dielectric portion20dis formed of a dielectric such as aluminum nitride or aluminum oxide. The dielectric portion20dhas a substantially disk shape. In an embodiment, the thickness of the dielectric portion20din the second region22is smaller than the thickness of the dielectric portion20din the first region21. The position in the vertical direction of the upper surface of the dielectric portion20din the second region22may be lower than the position in the vertical direction of the upper surface of the dielectric portion20din the first region21.

The first region21has the electrode21a(chuck electrode). The electrode21ais an electrode having a film shape and is provided in the dielectric portion20din the first region21. A direct-current power source55is connected to the electrode21athrough a switch56. When a direct-current voltage from the direct-current power source55is applied to the electrode21a,an electrostatic attraction force is generated between the first region21and the substrate W. Due to the generated electrostatic attraction force, the substrate W is attracted to the first region21and held by the first region21.

The first region21further has a first electrode21c.The first electrode21cis an electrode having a film shape and is provided in the dielectric portion20din the first region21. The electrode21amay extend closer to the upper surface of the first region21than the first electrode21cin the vertical direction.

The plasma processing apparatus1is further provided with a first bias power source61. The first bias power source61is electrically connected to the first electrode21cthrough a first circuit63. The first bias power source61generates a first electrical bias. The first electrical bias is applied to the first electrode21c.In an embodiment, the first electrical bias is a pulse wave that includes a pulse of a negative direct-current voltage and is periodically generated at a cycle that is defined by a bias frequency. The bias frequency may be a frequency in the range of 200 kHz to 13.56 MHz. The voltage level of the pulse wave may have a voltage value of 0 V or higher in a period other than a period in which the pulse of the negative direct-current voltage continues in the cycle, and the pulse wave may be, for example, a pulse wave having a positive or negative voltage value. Alternatively, the voltage of the pulse wave may have an absolute value lower than the absolute value of the voltage of the pulse in a period other than the period in which the pulse of the negative direct-current voltage continues in the cycle. The voltage level of the pulse may temporally change within the cycle, and the pulse may be a pulse voltage such as a triangular wave or an impulse.

FIG. 3illustrates a first bias power source, a damping circuit, a first circuit, and a filter in a plasma processing apparatus according to an exemplary embodiment. As shown inFIGS. 1 and 3, the plasma processing apparatus1may be further provided with a damping circuit62and a filter64. The damping circuit62may be connected between the first bias power source61and the first circuit63. The filter64may be connected between the first circuit63and the first electrode21c.The first bias power source61may be connected to the first circuit63without going through the damping circuit62. In this case, the plasma processing apparatus1may not be provided with the damping circuit62.

As shown inFIG. 3, in an embodiment, the first bias power source61includes a variable direct-current power source61p,a switch61a,and a switch61b.The variable direct-current power source61pis a direct-current power source that generates a negative direct-current voltage. The level of the direct-current voltage that is generated by the variable direct-current power source61pis variable. The variable direct-current power source61pis connected to an output610through the switch61a.The output610is connected to the ground through the switch61b.The switch61aand the switch61bcan be controlled by a controller MC (described later). In a case where the switch61ais in a conduction state and the switch61bis in a non-conduction state, a negative direct-current voltage is output from the output61o.In a case where the switch61ais in the non-conduction state and the switch61bis in the conduction state, the voltage level of the output610becomes 0 V. A pulse wave, which is the first electrical bias, can be obtained by controlling the conduction state of each of the switch61aand the switch61b.

The damping circuit62is connected between the output610of the first bias power source61and the first circuit63. In an embodiment, the damping circuit62has a resistor62rand a capacitor62c.One end of the resistor62ris connected to the output610of the first bias power source61. One end of the capacitor62cis connected to a node62non an electrical path connecting the other end of the resistor62rwith the first circuit63. The other end of the capacitor62cis grounded.

The impedance of the first circuit63may be variable. The first circuit63has one or more variable circuit elements. Each of the one or more variable circuit elements has a variable element parameter. In an embodiment, the first circuit63has a first variable resistor63rand a first variable capacitor63cas the one or more variable circuit elements. In the first circuit63, the variable element parameters are the resistance value of the first variable resistor63rand the capacitance of the first variable capacitor63c.One end of the first variable resistor63ris connected to the output610of the first bias power source61through the damping circuit62. One end of the first variable capacitor63cis connected to a node63non an electrical path connecting the other end of the first variable resistor63rwith the first electrode21c.The other end of the first variable capacitor63cis grounded. The impedance of the first circuit63is set by the controller MC. The impedance of the first circuit63is controlled by setting the variable element parameter of each of one or more variable circuit elements of the first circuit63, for example, the resistance value of the first variable resistor63rand the capacitance of the first variable capacitor63c,by the controller MC. The impedance of the first circuit63may be constant rather than variable. That is, a fixed resistor may be used instead of the first variable resistor63r,and a fixed capacitor may be used instead of the first variable capacitor63c.

The filter64is connected between the node63nand the first electrode21c.The filter64is an electric filter configured to block or attenuate the radio frequency power from the radio frequency power source57. The filter64includes, for example, an inductor connected between the node63nand the first electrode21c.

As shown inFIG. 1, the second region22extends to surround the first region21. The second region22is a substantially annular region. The central axis of the second region22substantially coincides with the axis AX. The second region22is configured to support the edge ring ER placed thereon (that is, on the upper surface thereof). The second region22shares the dielectric portion20dwith the first region21.

In an embodiment, the second region22may hold the edge ring ER by an electrostatic attraction force. In this embodiment, the second region22may have one or more electrodes (chuck electrodes). In the embodiment shown inFIG. 1, the second region22has a pair of electrodes, that is, the electrode22aand the electrode22b.The electrode22aand the electrode22bare provided in the dielectric portion20din the second region22. The electrode22aand the electrode22bconfigure a bipolar electrode. Each of the electrode22aand the electrode22bis an electrode having a film shape. The electrode22aand the electrode22bmay extend at substantially the same height position in the vertical direction.

A direct-current power source71is connected to the electrode22athrough a switch72and a filter73. The filter73is an electric filter configured to block or attenuate the radio frequency power and the first and second electrical biases. A direct-current power source74is connected to the electrode22bthrough a switch75and a filter76. The filter76is an electric filter configured to block or reduce the radio frequency power and the first and second electrical biases.

The direct-current power source71and the direct-current power source74apply direct-current voltages to the electrodes22aand22b,respectively, in order to generate an electrostatic attraction force that attracts the edge ring ER to the second region22. The setting potential of each of the electrodes22aand22bmay be any of positive potential, negative potential, and 0 V. For example, the potential of the electrode22amay be set to positive potential, and the potential of the electrode22bmay be set to negative potential. Further, the potential difference between the electrode22aand the electrode22bmay be formed by using a single direct-current power source instead of the two direct-current power sources.

When a direct-current voltage is applied to the electrode22aand the electrode22b,an electrostatic attraction force is generated between the second region22and the edge ring ER. The edge ring ER is attracted to the second region22by the generated electrostatic attraction force and held by the second region22.

The second region22further has a second electrode22c.The second electrode22cis an electrode having a film shape. The second electrode22cis provided in the dielectric portion20din the second region22. The second electrode22cis separated from the first electrode21c.The electrode22aand the electrode22bmay extend closer to the upper surface of the second region22than the second electrode22cin the vertical direction. The second electrode22cmay be disposed outside the second region22. For example, the second electrode22cmay be provided below the edge ring ER and in the outer peripheral portion29.

The plasma processing apparatus1is further provided with a second bias power source81. The second bias power source81is electrically connected to the second electrode22cthrough a second circuit83. The second bias power source81generates a second electrical bias. The second electrical bias is applied to the second electrode22c.In an embodiment, the second electrical bias is a pulse wave that includes a pulse of a negative direct-current voltage and is periodically generated at a cycle that is defined by the bias frequency. The bias frequency of the second electrical bias is the same as the bias frequency of the first electrical bias. The voltage level of the pulse wave may have a voltage value of 0 V or higher in a period other than a period in which the pulse of the negative direct-current voltage continues in the cycle, and the pulse wave may be, for example, a pulse wave having a positive or negative voltage value. Alternatively, the voltage of the pulse wave may have an absolute value lower than the absolute value of the voltage of the pulse in a period other than the period in which the pulse of the negative direct-current voltage continues in the cycle. The voltage level of the pulse may temporally change within the cycle, and the pulse may be a pulse voltage such as a triangular wave or an impulse.

FIG. 4illustrates a second bias power source, a damping circuit, a second circuit, and a filter in a plasma processing apparatus according to an exemplary embodiment. As shown inFIGS. 1 and 4, the plasma processing apparatus1may be further provided with a damping circuit82and a filter84. The damping circuit82may be connected between the second bias power source81and the second circuit83. The filter84may be connected between the second circuit83and the second electrode22c.The second bias power source81may be connected to the second circuit83without going through the damping circuit82. In this case, the plasma processing apparatus1may not be provided with the damping circuit82.

As shown inFIG. 4, in an embodiment, the second bias power source81includes a variable direct-current power source81p,a switch81a,and a switch81b.The variable direct-current power source81pis a direct-current power source that generates a negative direct-current voltage. The level of the direct-current voltage that is generated by the variable direct-current power source81pis variable. The variable direct-current power source81pis connected to an output810through the switch81a.The output810is connected to the ground through the switch81b.The switch81aand the switch81bcan be controlled by the controller MC (described later). In a case where the switch81ais in a conduction state and the switch81bis in a non-conduction state, a negative direct-current voltage is output from the output81o.In a case where the switch81ais in the non-conduction state and the switch81bis in the conduction state, the voltage level of the output810becomes 0 V. A pulse wave, which is the second electrical bias, can be obtained by controlling the conduction state of each of the switch81aand the switch81b.

The damping circuit82is connected between the output810of the second bias power source81and the second circuit83. In an embodiment, the damping circuit82has a resistor82rand a capacitor82c.One end of the resistor82ris connected to the output810of the second bias power source81. One end of the capacitor82cis connected to a node82non an electrical path connecting the other end of the resistor82rwith the second circuit83. The other end of the capacitor82cis grounded.

The impedance of the second circuit83may be variable. The second circuit83has one or more variable circuit elements. Each of the one or more variable circuit elements has a variable element parameter. In an embodiment, the second circuit83has a second variable resistor83rand a second variable capacitor83cas the one or more variable circuit elements. In the second circuit83, the variable element parameters are the resistance value of the second variable resistor83rand the capacitance of the second variable capacitor83c.

One end of the second variable resistor83ris connected to the output810of the second bias power source81through the damping circuit82. One end of the second variable capacitor83cis connected to a node83non an electrical path connecting the other end of the second variable resistor83rwith the second electrode22c.The other end of the second variable capacitor83cis grounded. The second circuit83has impedance higher than the impedance of the first circuit63at a common bias frequency of the first electrical bias and the second electrical bias. In an embodiment, the impedance of the first circuit63and the impedance of the second circuit83are set such that the ratio between an electric current that is supplied to the substrate W and an electric current that is supplied to the edge ring ER is equal to the ratio between an area of the substrate W and an area of the edge ring ER. The impedance of the second circuit83is set by the controller MC. The impedance of the second circuit83is controlled by setting the variable element parameter of each of one or more variable circuit elements of the second circuit83, for example, the resistance value of the second variable resistor83rand the capacitance of the second variable capacitor83c,by the controller MC. The impedance of the second circuit83may be constant rather than variable. That is, a fixed resistor may be used instead of the second variable resistor83r,and a fixed capacitor may be used instead of the second variable capacitor83c.

The filter84is connected between the node83nand the second electrode22c.The filter84is an electric filter configured to block or attenuate the radio frequency power from the radio frequency power source57. The filter84includes, for example, an inductor connected between the node83nand the second electrode22c.

The second region22may further have a gas line22g.The gas line22gis a gas line provided for supplying a heat transfer gas, for example, a He gas, to the gap between the second region22and the edge ring ER. The gas line22gis connected to a gas supply mechanism86which is a heat transfer gas source.

In an embodiment, as shown inFIG. 2, the plasma processing apparatus1is further provided with the controller MC. The controller MC is a computer which includes a processor, a storage device, an input device, a display device, and the like, and controls each part of the plasma processing apparatus1. Specifically, the controller MC executes a control program stored in the storage device, and controls each part of the plasma processing apparatus1, based on recipe data stored in the storage device. The process designated by the recipe data is performed in the plasma processing apparatus1under the control by the controller MC.

Here, the edge ring ER wears by being exposed to plasma, so that the thickness thereof decreases. In a case where the thickness of the edge ring ER becomes smaller than the initial thickness thereof, the upper end of a sheath (plasma sheath) is inclined in the vicinity of an edge of the substrate W. Therefore, in a case where the thickness of the edge ring ER becomes smaller than the initial thickness thereof, an incident direction of ions with respect to the edge of the substrate W is inclined with respect to the vertical direction. In an embodiment, the controller MC may control the second bias power source81to increase the setting level of the second electrical bias according to a decrease in the thickness of the edge ring ER. In a case where the second electrical bias is the pulse wave described above, the setting level of the second electrical bias is the absolute value of the voltage of the pulse in the pulse wave. When the setting level of the second electrical bias is increased, the thickness of the sheath increases above the edge ring ER, so that the inclination of the incident direction of the ions with respect to the edge of the substrate W can be corrected.

The controller MC may specify the setting level of the second electrical bias corresponding to the thickness of the edge ring ER by using a function or a table stored in the storage device thereof. The thickness of the edge ring ER may be measured optically or electrically, or may be estimated from a time in which the edge ring ER is exposed to plasma.

Further, the controller MC may control the variable element parameter of each of the one or more variable circuit elements of the second circuit83to reduce the impedance of the second circuit83according to the decrease in the thickness of the edge ring ER. The impedance of the second circuit83is reduced according to an increase in the setting level of the second electrical bias, whereby an increase in a time length that is required to reach a peak level from a base level in the voltage waveform of the edge ring ER is suppressed.

In the plasma processing apparatus1, the first electrode21cand the substrate W form a first capacitor element. Further, the second electrode22cand the edge ring ER form a second capacitor element. The region of the edge ring ER is smaller than the region of the substrate W. Therefore, the capacitance of the second capacitor element is lower than the capacitance of the first capacitor element. Therefore, when an electric current that is supplied to the first capacitor element and an electric current that is supplied to the second capacitor element are the same as each other, the voltage waveform of the edge ring ER changes at a higher speed than the voltage waveform of the substrate W. In the plasma processing apparatus1, the first circuit63is provided between the first electrode21cand the first bias power source61, and the second circuit83is provided between the second electrode22cand the second bias power source81. At the bias frequency, the impedance of the second circuit83is set to impedance higher than the impedance of the first circuit63. Therefore, according to the plasma processing apparatus1, the difference between the voltage waveform of the substrate W and the voltage waveform of the edge ring ER is reduced.

Hereinafter,FIGS. 5A and 5Bwill be referred to.FIG. 5Ais a diagram showing simulation results of voltage waveforms in the plasma processing apparatus shown inFIG. 1.FIG. 5Bis a diagram showing simulation results of voltage waveforms in a plasma processing apparatus of a comparative example. The plasma processing apparatus of the comparative example is a plasma processing apparatus in which the first circuit63and the second circuit83are removed from the plasma processing apparatus1. In each ofFIGS. 5A and 5B, the horizontal axis represents time and the vertical axis represents voltage. In each ofFIGS. 5A and 5B, the waveform of the output voltage (the second electrical bias) of the second bias power source81, the voltage waveform of the edge ring ER, and the voltage waveform of the substrate W are respectively indicated by a dashed-dotted line, a solid line, and a broken line. As shown inFIG. 5B, in the plasma processing apparatus of the comparative example which does not have the first circuit63and the second circuit83, a difference occurs between the voltage waveform of the substrate W and the voltage waveform of the edge ring ER. On the other hand, as shown inFIG. 5A, in the plasma processing apparatus1, the difference between the voltage waveform of the substrate W and the voltage waveform of the edge ring ER is reduced.

Hereinafter,FIGS. 6 and 7will be referred to.FIG. 6illustrates a first bias power source, a damping circuit, a first circuit, and a filter in a plasma processing apparatus according to an exemplary embodiment.FIG. 7illustrates a second bias power source, a damping circuit, a second circuit, and a filter in a plasma processing apparatus according to an exemplary embodiment. As shown inFIG. 6, the first circuit63may have a first variable inductor63i instead of the first variable resistor63r.Further, as shown inFIG. 7, the second circuit83may have a second variable inductor83iinstead of the second variable resistor83r.Although the example in which the first circuit and the second circuit include the variable elements is shown, the first circuit and/or the second circuit may not include the variable element.

Hereinafter,FIG. 8will be referred to.FIG. 8schematically illustrates a plasma processing apparatus according to another exemplary embodiment. A plasma processing apparatus1B shown inFIG. 8includes a radio frequency bias power source as the first bias power source61. The plasma processing apparatus1B includes a radio frequency bias power source as the second bias power source81. In the plasma processing apparatus1B, the first bias power source61is configured to generate radio frequency bias power having a bias frequency as the first electrical bias. The bias frequency is a frequency within the range of 200 kHz to 13.56 MHz, and is, for example, 400 kHz. In the plasma processing apparatus1B, the first bias power source61is connected to the first electrode21cthrough a matcher65and the first circuit63. The matcher65has a matching circuit for matching the impedance on the load side of the first bias power source61with the output impedance of the first bias power source61.

Further, in the plasma processing apparatus1B, the second bias power source81is configured to generate radio frequency bias power having a bias frequency as the second electrical bias. The bias frequency of the radio frequency bias power that is generated by the second bias power source81is the same as the bias frequency of the radio frequency bias power that is generated by the first bias power source61. Further, in the plasma processing apparatus1B, the second bias power source81is connected to the second electrode22cthrough a matcher85and the second circuit83. The matcher85has a matching circuit for matching the impedance on the load side of the second bias power source81with the output impedance of the second bias power source81. In the plasma processing apparatus1B, the setting level of the second electrical bias that is controlled by the controller MC is a power level of the radio frequency bias power. Other configurations of the plasma processing apparatus1B may be the same as the corresponding configurations of the plasma processing apparatus1.

Hereinafter,FIG. 9will be referred to.FIG. 9schematically illustrates a plasma processing apparatus according to still another exemplary embodiment. In a plasma processing apparatus1C shown inFIG. 9, the electrode22aand the electrode22bare used as the second electrode22c.The electrical path extending from the output of the second bias power source81is branched into two branch paths in a subsequent stage of the second circuit83(or the filter84), and the two branch paths are respectively connected to the electrode22aand the electrode22bthrough blocking capacitors87aand87b.Other configurations of the plasma processing apparatus1C may be the same as the corresponding configurations of the plasma processing apparatus1. Also in the plasma processing apparatus1B, similar to the plasma processing apparatus1C, the electrodes22aand22bmay be used as the second electrode to which the second electrical bias is applied, and the second electrode22cseparate from the electrodes22aand22bmay be omitted.

While various exemplary embodiments have been described above, various additions, omissions, substitutions and changes may be made without being limited to the exemplary embodiments described above. Elements of the different embodiments may be combined to form another embodiment.

For example, in another embodiment, the plasma processing apparatus may be a capacitively coupled plasma processing apparatus different from the plasma processing apparatus1. In another embodiment, the plasma processing apparatus may be another type of plasma processing apparatus. The other type of plasma processing apparatus may be an inductively coupled plasma processing apparatus, an electron cyclotron resonance (ECR) plasma processing apparatus, or a plasma processing apparatus that generates plasma by using surface waves such as microwaves.

Further, the first electrode21cand the second electrode22cmay not be provided in the dielectric portion20dof the electrostatic chuck20. Each of the first electrode21cand the second electrode22cmay be provided in another dielectric portion provided between the electrostatic chuck20and the lower electrode18.

Further, each of the one or more variable circuit elements in each of the first circuit63and the second circuit83is not a single variable circuit element, but may be configured with an array of a plurality of fixed circuit elements and a plurality of switching elements respectively connected to the plurality of fixed circuit elements. In this case, the number of fixed circuit elements that are connected in parallel is adjusted by controlling the plurality of switching elements.