Plasma processing apparatus and plasma processing method

Abstract

In a disclosed plasma processing apparatus, high-frequency power for generating plasma is supplied during a first period, and a power level at which the power level of the high-frequency power is reduced is set during a second period. During the second period, bias power is applied to a lower electrode of a substrate support. The bias power varies the potential of the substrate within each period defined by a second frequency. During the second period, a DC voltage is applied to an upper electrode. The DC voltage is set such that within each period defined by the second frequency, its polarity is negative during a first sub-period, and its absolute value during the first sub-period is greater than its absolute value during a second sub-period.

Description

Technical Field

[0001] Exemplary embodiments of the present invention 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 such as plasma etching. The plasma processing apparatus is configured to generate plasma in a chamber and process the substrate with chemical species from the plasma. As one type of plasma processing apparatus, a capacitively coupled plasma processing apparatus is known. The capacitively coupled plasma processing apparatus has an upper electrode and a lower electrode. A substrate support including the lower electrode supports the substrate in the chamber. The upper electrode is provided above the substrate support. The capacitively coupled plasma processing apparatus generates plasma from a gas in the chamber by generating a high-frequency electric field between the upper electrode and the lower electrode.

[0003] The capacitively coupled plasma processing apparatus described in Japanese Patent Application Laid-Open No. 2006-270017 has a DC power source connected to the upper electrode. The DC power source is configured to apply a negative-polarity DC voltage to the upper electrode. Summary of the Invention

[0004] The present invention provides a technique capable of supplying an adjusted amount of electrons from the upper electrode to the substrate.

[0005] In an exemplary embodiment, a plasma processing apparatus is provided. The plasma processing apparatus includes a chamber, a substrate support, an upper electrode, a high-frequency power supply, a bias power supply, a DC power supply, and a control unit. The substrate support includes a lower electrode. The substrate support is configured to support a substrate in the chamber. The upper electrode is disposed above the lower electrode. The high-frequency power supply is configured to supply high-frequency power having a first frequency to generate plasma from a gas in the chamber. The bias power supply is electrically connected to the lower electrode. The bias power supply is configured to supply bias power to introduce ions to the substrate placed on the substrate support. The bias power varies the potential of the substrate placed on the substrate support within each period defined by a second frequency. The DC power supply is electrically connected to the upper electrode. The control unit is configured to control the high-frequency power supply, the bias power supply, and the DC power supply. The control unit controls the high-frequency power supply to supply high-frequency power during a first period. The control unit controls the high-frequency power supply to set the power level of the high-frequency power in a second period after the first period to a power level reduced from the power level of the high-frequency power in the first period. The control unit controls the bias power supply to apply the bias power to the lower electrode during the second period. The control unit controls the DC power supply to apply a DC voltage to the upper electrode during the second period. The DC voltage in the second period is set such that within each period defined by the second frequency, its polarity is negative in a first sub-period, and its absolute value in the first sub-period is greater than its absolute value in a second sub-period different from the first sub-period.

[0006] According to one exemplary embodiment, an adjusted amount of electrons can be supplied from the upper electrode to the substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a diagram schematically showing a plasma processing apparatus according to an exemplary embodiment.

[0008] Figure 2 is a flowchart of a plasma processing method according to an exemplary embodiment.

[0009] Figure 3 is Figure 1 a timing chart of an example of the level of the bias power BP, the power level of the high-frequency power RF, the potential, and the DC voltage DCS in the plasma processing apparatus shown.

[0010] Figure 4 is a timing chart showing another example of the bias power.

[0011] Figure 5 is Figure 1 a timing chart of another example of the level of the bias power BP, the power level of the high-frequency power RF, the potential (the potential of the substrate W or the lower electrode 18), and the DC voltage DCS in the plasma processing apparatus shown.

[0012] Figure 6 It is a timing chart of another example of the DC voltage DCS. Detailed implementation

[0013] Hereinafter, various exemplary embodiments will be described.

[0014] In one exemplary embodiment, a plasma processing apparatus is provided. The plasma processing apparatus includes a chamber, a substrate support, an upper electrode, a high-frequency power supply, a bias power supply, a DC power supply, and a control unit. The substrate support includes a lower electrode. The substrate support is configured to support a substrate in the chamber. The upper electrode is disposed above the lower electrode. The high-frequency power supply is configured to supply high-frequency power having a first frequency in order to generate plasma from the gas in the chamber. The bias power supply is electrically connected to the lower electrode. The bias power supply is configured to supply bias power in order to introduce ions into the substrate placed on the substrate support. The bias power varies the potential of the substrate placed on the substrate support within each period defined by a second frequency. The DC power supply is electrically connected to the upper electrode. The control unit is configured to control the high-frequency power supply, the bias power supply, and the DC power supply. The control unit controls the high-frequency power supply so as to supply high-frequency power during a first period. The control unit controls the high-frequency power supply so as to set the power level of the high-frequency power in a second period after the first period to a power level reduced from the power level of the high-frequency power in the first period. The control unit controls the bias power supply so as to apply bias power to the lower electrode during the second period. The control unit controls the DC power supply so as to apply a DC voltage to the upper electrode during the second period. The DC voltage in the second period is set such that in each period defined by the second frequency, its polarity is negative in a first sub-period, and its absolute value in the first sub-period is greater than its absolute value in a second sub-period different from the first sub-period.

[0015] According to the above embodiment, it is possible to set the potential polarity of the substrate when a DC voltage with a large absolute value and a negative polarity is applied to the upper electrode. In a state where a DC voltage with a large absolute value and a negative polarity is applied to the upper electrode when the potential of the substrate is a positive potential, a relatively large amount of electrons are supplied to the substrate. On the other hand, in a state where a DC voltage with a large absolute value and a negative polarity is applied to the upper electrode when the potential of the substrate is a negative potential, the amount of electrons supplied to the substrate is small. Therefore, according to the above embodiment, it is possible to supply an adjusted amount of electrons from the upper electrode to the substrate. And, in a state where a DC voltage with a large absolute value and a negative polarity is applied to the upper electrode when the potential of the substrate is a positive potential, the degree of dissociation of the gas in the chamber is low. On the other hand, in a state where a DC voltage with a large absolute value and a negative polarity is applied to the upper electrode when the potential of the substrate is a negative potential, the degree of dissociation of the gas in the chamber is high. Therefore, according to the above embodiment, it is possible to set the degree of dissociation of the gas in the chamber to an adjusted degree of dissociation during the second period.

[0016] In an exemplary embodiment, the control unit may control the DC power supply such that the absolute value of the DC voltage when the bias power has a positive potential during the second period is greater than the absolute value of the DC voltage when the bias power has a negative potential during the second period.

[0017] In an exemplary embodiment, the control unit may control the DC power supply such that the absolute value of the DC voltage when the bias power has a negative potential during the second period is greater than the absolute value of the DC voltage when the bias power has a positive potential during the second period.

[0018] In an exemplary embodiment, the control unit may control the high-frequency power supply and the bias power supply such that the supply of the high-frequency power and the supply of the bias power are stopped during the period between the first period and the second period.

[0019] In an exemplary embodiment, the control unit may control the DC power supply such that the DC voltage is applied to the upper electrode during the period between the first period and the second period. The DC voltage applied to the upper electrode during the period between the first period and the second period has an absolute value smaller than the minimum absolute value of the DC voltage applied to the upper electrode during the first sub-period and has a negative polarity. According to this embodiment, during the period between the first period and the second period, a relatively small amount of electrons are released from the upper electrode into the chamber. As a result, the plasma can be reliably maintained even during the period between the first period and the second period.

[0020] In an exemplary embodiment, the control unit may control the DC power supply such that the DC voltage is applied to the upper electrode during the first period, and the DC voltage has an absolute value smaller than the minimum absolute value of the DC voltage applied to the upper electrode during the first sub-period and has a negative polarity.

[0021] In an exemplary embodiment, the level of the DC voltage applied to the upper electrode by the DC power supply during the first sub-period may also change in such a way as to maintain a constant potential difference between the upper electrode and the lower electrode.

[0022] In an exemplary embodiment, the level of the DC voltage during the second sub-period may be zero.

[0023] In an exemplary embodiment, the bias power may be high-frequency bias power having a second frequency.

[0024] In an exemplary embodiment, the bias power may be a DC voltage whose polarity is negative during one of the two sub-periods within each period defined by the second frequency. In this embodiment, the bias power may be a DC voltage whose level is zero or whose polarity is negative and whose absolute value is smaller than its absolute value during one of the two sub-periods during the other sub-period.

[0025] In another exemplary embodiment, a plasma processing method is provided. The plasma processing apparatus used in the plasma processing method includes a chamber, a substrate support, an upper electrode, a high-frequency power supply, a bias power supply, a DC power supply, and a control unit. The substrate support includes a lower electrode. The substrate support is configured to support a substrate in the chamber. The upper electrode is disposed above the lower electrode. The high-frequency power supply is configured to supply high-frequency power having a first frequency in order to generate plasma from the gas in the chamber. The bias power supply is electrically connected to the lower electrode. The bias power supply is configured to supply bias power in order to introduce ions to the substrate placed on the substrate support. The bias power varies the potential of the substrate placed on the substrate support within each period defined by a second frequency. The DC power supply is electrically connected to the upper electrode. The plasma processing method includes a step of supplying high-frequency power during a first period. The plasma processing method further includes a step of setting the power level of the high-frequency power in a second period after the first period to a power level reduced from the power level of the high-frequency power in the first period. The plasma processing method further includes a step of applying bias power to the lower electrode within the second period. The plasma processing method further includes a step of applying a DC voltage from the DC power supply to the upper electrode during the second period. The DC voltage is set such that in each period defined by the second frequency, its polarity is negative in a first sub-period, and its absolute value in the first sub-period is greater than its absolute value in a second sub-period different from the first sub-period.

[0026] Hereinafter, various exemplary embodiments will be described in detail with reference to the accompanying drawings. In addition, in each of the drawings, the same or equivalent parts are denoted by the same reference numerals.

[0027] Figure 1 is a diagram schematically showing a plasma processing apparatus according to an exemplary embodiment. Figure 1 The illustrated plasma processing apparatus 1 is a capacitively coupled plasma processing apparatus. The plasma processing apparatus 1 includes a chamber 10. An internal space 10s is provided in the chamber 10. The central axis of the internal space 10s is an axis AX extending in the vertical direction.

[0028] In one embodiment, the chamber 10 includes 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. On the inner wall surface of the chamber body 12, that is, the wall surface defining the internal space 10s, a film having plasma resistance is formed. The film may be a ceramic film such as a film formed by an anodizing process or a film formed of yttrium oxide.

[0029] A passage 12p is formed in the side wall of the chamber main body 12. When being transported between the internal space 10s and the outside of the chamber 10, the substrate W passes through the passage 12p. In order to open and close the passage 12p, a gate valve 12g is provided along the side wall of the chamber main body 12.

[0030] 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 support 16 is supported by a support portion 17. The support portion 17 extends upward from the bottom of the chamber main body 12. The support portion 17 has a substantially cylindrical shape. The support portion 17 is formed of an insulating material such as quartz.

[0031] The substrate support 16 has a lower electrode 18 and an electrostatic chuck 20. The lower electrode 18 and the electrostatic chuck 20 are provided in the chamber 10. The lower electrode 18 is formed of a conductive material such as aluminum and has a substantially disc shape.

[0032] A flow path 18f is formed in the lower electrode 18. The flow path 18f is a flow path for a heat exchange medium. As the heat exchange medium, a liquid refrigerant or a refrigerant (e.g., chlorofluorocarbon) that cools the lower electrode 18 by its vaporization is used. A supply device (e.g., a cooling unit) of the heat exchange medium is connected to the flow path 18f. This supply device is provided outside the chamber 10. The heat exchange medium is supplied from the supply device to the flow path 18f via a pipe 23a. The heat exchange medium supplied to the flow path 18f returns to the supply device via a pipe 23b.

[0033] The electrostatic chuck 20 is provided on the lower electrode 18. When being processed in the internal space 10s, the substrate W is placed on the electrostatic chuck 20 and held by the electrostatic chuck 20.

[0034] The electrostatic chuck 20 has a main body and an electrode. The main body of the electrostatic chuck 20 is formed of a dielectric such as alumina or aluminum nitride. The main body of the electrostatic chuck 20 has a substantially disc shape. The central axis of the electrostatic chuck 20 substantially coincides with the axis AX. The electrode of the electrostatic chuck 20 is provided in the main body. The electrode of the electrostatic chuck 20 has a film shape. A DC power supply is electrically connected to the electrode of the electrostatic chuck 20 via a switch. When a voltage from the DC power supply is applied to the electrode of the electrostatic chuck 20, an electrostatic attraction force is generated between the electrostatic chuck 20 and the substrate W. By the generated electrostatic attraction force, the substrate W is attracted to the electrostatic chuck 20 and held by the electrostatic chuck 20.

[0035] The electrostatic chuck 20 includes a substrate placement area. The substrate placement area is an area having a substantially disc shape. The central axis of the substrate placement area substantially coincides with the axis AX. When being processed in the chamber 10, the substrate W is placed on the upper surface of the substrate placement area.

[0036] In one embodiment, the electrostatic chuck 20 may further include an edge ring placement area. The edge ring placement area extends circumferentially so as to surround the substrate placement area around the central axis of the electrostatic chuck 20. An edge ring ER is mounted on the upper surface of the edge ring placement area. The edge ring ER has a ring shape. The edge ring ER is placed on the edge ring placement area with its central axis coinciding with the axis AX. The substrate W is disposed within the area surrounded by the edge ring ER. That is, the edge ring ER is configured to surround the edge of the substrate W. The edge ring ER may have conductivity. The edge ring ER is formed of, for example, silicon or silicon carbide. The edge ring ER may be formed of a dielectric such as quartz.

[0037] The plasma processing apparatus 1 may further include a gas supply pipe 25. The gas supply pipe 25 supplies a heat transfer gas, such as He gas, from the 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.

[0038] The plasma processing apparatus 1 may further include an insulating region 27. The insulating region 27 is disposed on the support portion 17. The insulating region 27 is disposed radially outside the lower electrode 18 with respect to the axis AX. The insulating region 27 extends circumferentially along the outer peripheral surface of the lower electrode 18. The insulating region 27 is formed of an insulator such as quartz. The edge ring ER is placed on the insulating region 27 and the edge ring placement area.

[0039] 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 and the component 32 together close the upper opening of the chamber body 12. The component 32 has insulating properties. The upper electrode 30 is supported on the upper part of the chamber body 12 via the component 32.

[0040] The upper electrode 30 includes a top plate 34 and a support body 36. The lower surface of the top plate 34 defines the internal space 10s. A plurality of exhaust holes 34a are formed in the top plate 34. The plurality of exhaust holes 34a penetrate the top plate 34 in the plate thickness direction (vertical direction) respectively. The top plate 34 is not limited and 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 component. The film may be a ceramic film such as a film formed by anodizing treatment or a film formed of yttrium oxide.

[0041] The support body 36 detachably supports the top plate 34. The support body 36 is formed of a conductive material such as aluminum, for example. A gas diffusion chamber 36a is provided inside the support body 36. A plurality of gas holes 36b extend downward from the gas diffusion chamber 36a. The plurality of gas holes 36b communicate with the plurality of exhaust holes 34a respectively. A gas introduction port 36c is formed in the support body 36. 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.

[0042] A gas source group 40 is connected to a gas supply pipe 38 via a valve group 41, a flow controller group 42, and a valve group 43. A gas supply unit GS is constituted by the gas source group 40, the valve group 41, the flow controller group 42, and the valve group 43. The gas source group 40 includes a plurality of gas sources. The valve group 41 and the valve group 43 each include a plurality of valves (such as on-off valves). The flow controller group 42 includes a plurality of flow controllers. The plurality of flow controllers in the flow controller group 42 are respectively mass flow controllers or pressure-controlled flow controllers. The plurality of gas sources in the gas source group 40 are respectively connected to the gas supply pipe 38 via the valves corresponding to the valve group 41, the flow controllers corresponding to the flow controller group 42, and the valves corresponding to the valve group 43. The plasma processing apparatus 1 can supply gases from one or more gas sources selected from the plurality of gas sources in the gas source group 40 to the internal space 10s at respectively adjusted flow rates.

[0043] A baffle 48 is provided between the substrate support 16 or the support portion 17 and the side wall of the chamber body 12. The baffle 48 can be constituted, for example, by coating a ceramic such as yttrium oxide on an aluminum member. A plurality of through holes are formed in the baffle 48. Below the baffle 48, an exhaust pipe 52 is connected to the bottom of the chamber body 12. An exhaust device 50 is connected to the exhaust pipe 52. 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.

[0044] The plasma processing apparatus 1 further includes a high-frequency power supply 61. The high-frequency power supply 61 is a power supply that generates high-frequency power RF. The high-frequency power RF is used to generate plasma from the gas in the chamber 10. The high-frequency power RF has a first frequency. The first frequency is a frequency in the range of 27 to 100 MHz, such as a frequency of 40 MHz or 60 MHz. In order to supply the high-frequency power RF to the lower electrode 18, the high-frequency power supply 61 is connected to the lower electrode 18 via a matching circuit 63. The matching circuit 63 is configured to match the output impedance of the high-frequency power supply 61 with the impedance on the load side (the lower electrode 18 side). In addition, the high-frequency power supply 61 may not be electrically connected to the lower electrode 18, but may be connected to the upper electrode 30 via the matching circuit 63.

[0045] The plasma processing apparatus 1 further includes a bias power supply 62. The bias power supply 62 is electrically connected to the lower electrode 18. In one embodiment, the bias power supply 62 is connected to the lower electrode 18 via a circuit 64. The bias power supply 62 is configured to generate a bias power BP supplied to the lower electrode 18. The bias power BP is used to introduce ions into the substrate W placed on the substrate support 16. The bias power BP is set such that the potential of the substrate W placed on the substrate support 16 varies within each period defined by the second frequency. The bias power BP can vary the potential of the substrate W placed on the substrate support 16 between a positive potential and a negative potential within each period defined by the second frequency. The second frequency may be a frequency lower than the first frequency. For example, the second frequency is 50 kHz or more and 27 MHz or less.

[0046] In one embodiment, the bias power BP is a high-frequency bias power. The high-frequency bias power is a high-frequency power having the second frequency. When the bias power BP is a high-frequency bias power, the circuit 64 is a matching circuit configured to match the output impedance of the bias power BP with the impedance on the load side (the lower electrode 18 side).

[0047] Alternatively, the bias power supply 62 may be configured to periodically apply a pulse NP of a negative-polarity DC voltage to the lower electrode 18 within a period CY defined by the second frequency (see Figure 4 ). Each period CY includes two sub-periods Pc and Pd. The pulse NP of the negative-polarity DC voltage is applied to the lower electrode 18 during one of these two sub-periods Pd. During the other sub-period Pc of these two sub-periods, the pulse NP of the negative-polarity DC voltage is not applied to the lower electrode 18. Alternatively, the absolute value of the DC voltage applied from the bias power supply 62 to the lower electrode 18 during the sub-period Pc may be less than the absolute value of the DC voltage (i.e., the pulse NP of the negative-polarity DC voltage) applied from the bias power supply 62 to the lower electrode 18 during the sub-period Pd. That is, the DC voltage applied from the bias power supply 62 to the lower electrode 18 during one of the two sub-periods Pc and Pd has a first negative level. The DC voltage applied from the bias power supply 62 to the lower electrode 18 during the other sub-period of the two sub-periods Pc and Pd has a zero level or a second negative level. The second negative level is higher than the first negative level. When the pulse NP of the negative-polarity DC voltage is applied to the lower electrode 18 as the bias power BP, the circuit 64 may be a low-pass filter.

[0048] The plasma processing apparatus 1 further includes a DC power supply 70. The DC power supply 70 is electrically connected to the upper electrode 30. The DC power supply 70 is configured to generate a DC voltage DCS applied to the upper electrode 30.

[0049] In one embodiment, the plasma processing apparatus 1 may further include a voltage sensor 78. The voltage sensor 78 is configured to directly or indirectly measure the potential of the substrate W. In Figure 1 the example shown, the voltage sensor 78 is configured to measure the potential of the lower electrode 18. Specifically, the voltage sensor 78 measures the potential of the power supply line connected between the lower electrode 18 and the bias power supply 62.

[0050] When plasma processing is performed in the plasma processing apparatus 1, a gas is supplied to the internal space 10s. Then, by supplying high-frequency power RF, the gas is excited in the internal space 10s. As a result, plasma is generated in the internal space 10s. The substrate W supported by the substrate support 16 is processed by chemical species such as ions and radicals from the plasma. For example, the substrate is etched by chemical species from the plasma. In the plasma processing apparatus 1, by supplying bias power BP to the lower electrode 18, positive ions from the plasma are accelerated toward the substrate W. And, in the plasma processing apparatus 1, by applying a negative-polarity DC voltage to the upper electrode 30, the positive ions from the plasma collide with the upper electrode 30 (top plate 34). As a result, electrons are released from the upper electrode 30. When the electrons released from the upper electrode 30 are supplied to the substrate W, the charge amount of the substrate W caused by positive charges decreases. As a result, positive ions can reach the bottom of the opening formed in the substrate W.

[0051] The plasma processing apparatus 1 further includes 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. The control unit MC executes a control program stored in the storage device and controls each part of the plasma processing apparatus 1 according to the process data stored in the storage device. Through the control based on the control unit MC, the process specified by the process data is executed in the plasma processing apparatus 1. The plasma processing method described later can be executed in the plasma processing apparatus 1 through the control of each part of the plasma processing apparatus 1 based on the control unit MC.

[0052] Hereinafter, with reference to Figures 2 to 6 . Figure 2 is a flowchart of a plasma processing method according to an exemplary embodiment. Figure 3 is Figure 1 a timing chart of an example of the level of the bias power BP, the power level of the high-frequency power RF, the potential (the potential of the substrate W or the lower electrode 18), and the DC voltage DCS in the plasma processing apparatus shown. Figure 4 is a timing chart showing another example of the bias power. Figure 5 is Figure 1A timing chart of another example of the level of the bias power BP, the power level of the high-frequency power RF, the potential (the potential of the substrate W or the lower electrode 18), and the DC voltage DCS in the plasma processing apparatus shown. Figure 6 is a timing chart of another example of the DC voltage DCS. Hereinafter, with reference to Figures 2 to 6 , a plasma processing method (hereinafter referred to as "method MT") according to an exemplary embodiment will be described. In addition, the control of the high-frequency power supply 61, the bias power supply 62, and the DC power supply 70 by the control unit MC will be described.

[0053] The method MT is executed in a state where the substrate W is placed on the substrate support 16. The method MT includes a step ST1, steps ST21, ST22, and ST23. The method MT may further include a step STM. In each execution of these steps of the method MT, the gas from the gas supply unit GS can be supplied into the chamber 10. And, in each execution of these steps of the method MT, the pressure of the gas in the chamber 10 is set to a specified pressure. To execute each of these steps of the method MT, the control unit MC controls the gas supply unit GS and the exhaust device 50.

[0054] The step ST1 is executed in the first period P1. The steps ST21, ST22, and ST23 are executed in the second period P2 after the first period P1. By executing the step ST1, in the first period P1, as Figure 3 and Figure 5 shown, the high-frequency power RF is supplied from the high-frequency power supply 61. In Figure 3 and Figure 5 , the power level of the high-frequency power RF in the first period P1 is represented as the "H" level, that is, the high level. In the first period P1, a continuous wave of the high-frequency power RF may be supplied. Or, in the first period P1, pulses of the high-frequency power RF may be supplied periodically. To execute the step ST1, the control unit MC controls the high-frequency power supply 61 so as to supply the high-frequency power RF in the first period P1. By executing the step ST1, plasma is generated from the gas in the chamber 10.

[0055] When the bias power BP is a high-frequency bias power, in the first period P1, the high-frequency bias power is not supplied to the lower electrode 18. Or, when the bias power BP is a high-frequency bias power, in the first period P1, the power level of the high-frequency bias power is set to a power level lower than the power level ("H" level) of the high-frequency bias power in the second period P2. In addition, in Figure 3 and Figure 5 , the power level of the high-frequency bias power in the first period P1 is represented as the "L" level.

[0056] As described above, the bias power BP can be a pulse NP of a negative-polarity DC voltage that is periodically applied to the lower electrode 18 in the period CY (refer to Figure 4 ). In the case where the pulse NP of the negative-polarity DC voltage is used as the bias power BP, in the first period P1, the pulse NP of the negative-polarity DC voltage is not applied to the lower electrode 18. Alternatively, the level of the pulse NP of the negative-polarity DC voltage in the first period P1 is set to be less than the absolute value of the absolute value of the pulse NP of the negative-polarity DC voltage in the second period P2 ("H" level). Additionally, in Figure 4 , the absolute value of the pulse NP of the negative-polarity DC voltage in the first period P1 is expressed as an "L" level.

[0057] As described above, the bias power BP varies the potential of the substrate W or the lower electrode 18 within each period CY. As Figure 3 and Figure 4 shown, in the first period P1, when the bias power BP is not supplied to the lower electrode 18, the potential of the substrate W or the lower electrode 18 can be zero.

[0058] In the first period P1, the negative-polarity DC voltage DCS may not be applied from the DC power supply 70 to the upper electrode 30. Alternatively, in the first period P1, the negative-polarity DC voltage DCS may also be applied from the DC power supply 70 to the upper electrode 30. The DC voltage DCS applied to the upper electrode 30 in the first period P1 has an absolute value smaller than the minimum absolute value of the negative-polarity DC voltage DCS applied to the upper electrode 30 in the first sub-period Pa within each period CY in the second period P2. In Figure 3 and Figure 5 , the level of the DC voltage DCS (the fourth negative-polarity DC voltage) applied to the upper electrode 30 in the first period P1 is expressed as a "V1" level. And the level of the negative-polarity DC voltage DCS applied to the upper electrode 30 in the first sub-period Pa is expressed as a "VH" level. Additionally, each period CY includes a first sub-period Pa and a second sub-period Pb. The second sub-period Pb is a period different from the first sub-period Pa.

[0059] In the first period P1, the control unit MC controls the high-frequency power supply 61, the bias power supply 62, and the DC power supply 70 so as to set the power level of the high-frequency power RF, the level of the bias power BP, and the absolute value of the negative-polarity DC voltage DCS as described above.

[0060] In one embodiment, the process STM may also be performed between the process ST1 and the process ST21. The process STM is performed during a period PM (break period) between the first period P1 and the second period P2. By performing the process STM, the supply of the high-frequency power RF and the supply of the bias power BP are stopped during the period PM. To perform the process STM, the control unit MC controls the high-frequency power supply 61 to stop the supply of the high-frequency power RF during the period PM. Further, to perform the process STM, the control unit MC controls the bias power supply 62 to stop the supply of the bias power during the period PM. When the plasma process performed in the method MT is plasma etching, the amount of deposits on the substrate W may increase during the period PM. Alternatively, in addition to this, the discharge of reaction products from within the opening formed in the substrate W is promoted during the period PM.

[0061] During the period PM, the negative-polarity DC voltage DCS may not be applied from the DC power supply 70 to the upper electrode 30. Alternatively, during the period PM, the negative-polarity DC voltage DCS (the third negative-polarity DC voltage) may be applied from the DC power supply 70 to the upper electrode 30. The absolute value of the DC voltage DCS applied to the upper electrode 30 during the period PM is smaller than the minimum absolute value of the negative-polarity DC voltage DCS applied to the upper electrode 30 during the first sub-period Pa. Further, in Figure 3 and Figure 5 , the level of the DC voltage DCS applied to the upper electrode 30 during the period PM is represented as the "VM" level. During the period PM, the control unit MC controls the DC power supply 70 to set the level of the DC voltage DCS as described above. When the negative-polarity DC voltage DCS having this absolute value is applied to the upper electrode during the period PM, a relatively small amount of electrons are released from the upper electrode 30 into the chamber 10. As a result, the plasma can be reliably maintained during the period PM.

[0062] As described above, the processes ST21, ST22, and ST23 are performed during the second period P2 after the first period P1. By performing the process ST21, during the second period P2, the power level (the second power level) of the high-frequency power RF is set to a power level that is reduced from the power level (the first power level) of the high-frequency power RF during the first period P1. The power level of the high-frequency power RF during the second period P2 may be zero. That is, the supply of the high-frequency power RF during the second period P2 may be stopped. To perform the process ST21, the control unit MC controls the high-frequency power supply 61 to set the power level of the high-frequency power RF during the second period P2 to this power level.

[0063] Process ST22 is executed during the execution of process ST21. By executing process ST22, during the second period P2, the bias power BP is supplied from the bias power supply 62 to the lower electrode 18. As described above, the bias power BP is set such that the potential of the substrate W placed on the substrate support 16 varies between a positive potential and a negative potential within each cycle CY defined by the second frequency. As described above, the bias power BP may be a high-frequency bias power. Alternatively, as described above, the bias power BP can include pulses NP of a DC voltage of a negative polarity that are periodically applied to the lower electrode 18 within the cycle CY defined by the second frequency. To execute process ST22, the control unit MC controls the bias power supply 62 so as to apply the bias power BP to the lower electrode 18 during the second period P2.

[0064] Process ST23 is executed during the execution of process ST21 and process ST22. By executing process ST23, during the second period P2, the DC voltage DCS is applied from the DC power supply 70 to the upper electrode 30. The DC voltage DCS during the second period P2 is set such that its polarity is negative during the first sub-period Pa within each cycle CY, and its absolute value during the first sub-period Pa is greater than its absolute value during the second sub-period Pb. In Figure 3 and Figure 5 the level of the DC voltage DCS (the DC voltage of the first negative polarity) during the first sub-period Pa is represented as the "VH" level. During the second sub-period Pb, the DC voltage DCS may not be applied to the upper electrode 30. Alternatively, the DC voltage DCS (the DC voltage of the second negative polarity) applied to the upper electrode 30 during the second sub-period Pb may also be set such that its polarity is negative and its absolute value is less than its absolute value during the first sub-period Pa. In Figure 3 and Figure 5 the level of the DC voltage DCS during the second sub-period Pb is represented as the "VL" level. To execute process ST23, the control unit MC controls the DC power supply 70 so as to apply the DC voltage DCS to the upper electrode 30 during the second period P2.

[0065] In one embodiment, as Figure 6 shown, the level of the DC voltage DCS applied to the upper electrode 30 by the DC power supply 70 during the first sub-period Pa may also vary in such a way as to maintain a constant potential difference between the upper electrode 30 and the lower electrode 18. According to this embodiment, it is possible to narrow the distribution of the energy of the electrons released from the upper electrode 30 and supplied to the substrate W.

[0066] In one embodiment, as Figure 3As shown, the DC voltage DCS can also be set such that its absolute value is greater when the substrate W or the lower electrode 18 has a positive potential than when the substrate W or the lower electrode 18 has a negative potential. For example, the DC voltage DCS can also be set such that its absolute value is greater when the bias power BP has a positive potential than when the bias power BP has a negative potential. In this embodiment, the first sub-period Pa is set to repeat during the period when the substrate W or the lower electrode 18 has a positive potential. And the second sub-period Pb is set to repeat during the period when the substrate W or the lower electrode 18 has a negative potential. The first sub-period Pa and the second sub-period Pb can be stored as pre-determined data in the storage device of the control unit MC, or can be specified by the control unit MC using this data. Alternatively, the first sub-period Pa and the second sub-period Pb can also be specified by the control unit MC according to the potential measured by the voltage sensor 78. In this embodiment, when the potential of the substrate W is positive, the DC voltage DCS with a larger absolute value is applied to the upper electrode 30. Therefore, the amount of electrons released from the upper electrode 30 and supplied to the substrate W increases.

[0067] In one embodiment, as Figure 5 shown, the DC voltage DCS can also be set such that its absolute value is greater when the substrate W or the lower electrode 18 has a negative potential than when the substrate W or the lower electrode 18 has a positive potential. For example, the DC voltage DCS can also be set such that its absolute value is greater when the bias power BP has a negative potential than when the bias power BP has a positive potential. In this embodiment, the first sub-period Pa is set to repeat during the period when the substrate W or the lower electrode 18 has a negative potential. And the second sub-period Pb is set to repeat during the period when the substrate W or the lower electrode 18 has a positive potential. The first sub-period Pa and the second sub-period Pb can be stored as pre-determined data in the storage device of the control unit MC, or can be specified by the control unit MC using this data. Alternatively, the first sub-period Pa and the second sub-period Pb can also be specified by the control unit MC according to the potential measured by the voltage sensor 78. In this embodiment, when the potential of the substrate W is negative, the DC voltage DCS with a larger absolute value is applied to the upper electrode 30. Therefore, the amount of electrons released from the upper electrode 30 and supplied to the substrate W decreases. In this embodiment, the electrons released from the upper electrode 30 increase the degree of dissociation of the gas in the chamber 10.

[0068] As Figure 2As shown, in one embodiment, a cycle including process ST1, process ST21, process ST22, and process ST23 can be repeated. This cycle can also include process STM. At this time, in process STJ, it is determined whether the stop condition is satisfied. The stop condition is satisfied when the number of executions of the cycle reaches a specified number. When it is determined in process STJ that the stop condition is not satisfied, the cycle is repeated. When it is determined in process STJ that the stop condition is satisfied, method MT ends.

[0069] As described above, in the plasma processing apparatus 1, it is possible to set the potential polarity of the substrate W when a DC voltage DCS with a large absolute value and a negative polarity is applied to the upper electrode 30. In a state where a DC voltage DCS with a large absolute value and a negative polarity is applied to the upper electrode 30 when the potential of the substrate W is a positive potential, a relatively large amount of electrons are supplied to the substrate W. On the other hand, in a state where a DC voltage DCS with a large absolute value and a negative polarity is applied to the upper electrode 30 when the potential of the substrate W is a negative potential, the amount of electrons supplied to the substrate W is small. Therefore, it is possible to supply an adjusted amount of electrons from the upper electrode 30 to the substrate W. And, in a state where a DC voltage DCS with a large absolute value and a negative polarity is applied to the upper electrode 30 when the potential of the substrate W is a positive potential, the degree of dissociation of the gas in the chamber 10 is low. On the other hand, in a state where a DC voltage DCS with a large absolute value and a negative polarity is applied to the upper electrode 30 when the potential of the substrate W is a negative potential, the degree of dissociation of the gas in the chamber 10 is high. Therefore, it is possible to set the degree of dissociation of the gas in the chamber 10 to an adjusted degree of dissociation during the second period P2.

[0070] As described above, various exemplary embodiments have been described, but the present invention is not limited to the above exemplary embodiments, and various additions, omissions, substitutions, and changes can be made. Also, elements in different embodiments can be combined to form other embodiments.

[0071] From the above description, it can be understood that the various embodiments of the present invention have been described in this specification for illustrative purposes, and various changes can be made without departing from the scope and spirit of the present invention. Therefore, the various embodiments disclosed in this specification are not intended to be limiting, and the true scope and spirit can be shown by the scope of the appended claims.

Claims

1. A plasma processing apparatus, comprising: a chamber; a substrate support having a lower electrode and configured to support a substrate in the chamber; an upper electrode disposed above the lower electrode; a high-frequency power supply configured to supply high-frequency power having a first frequency to generate plasma from a gas in the chamber; a bias power supply which is a bias power supply electrically connected to the lower electrode and configured to supply bias power that varies the potential of the substrate placed on the substrate support within each period defined by a second frequency in order to introduce ions to the substrate placed on the substrate support; a DC power supply electrically connected to the upper electrode; and a control unit configured to control the high-frequency power supply, the bias power supply, and the DC power supply, wherein the control unit performs the following control: controlling the high-frequency power supply to supply the high-frequency power during a first period and setting the power level of the high-frequency power in a second period after the first period to a power level reduced from the power level of the high-frequency power in the first period; controlling the bias power supply to apply the bias power to the lower electrode during the second period; and controlling the DC power supply to apply a DC voltage to the upper electrode during the second period, the DC voltage being set such that in each period defined by the second frequency, its polarity is negative in a first sub-period and its absolute value in the first sub-period is greater than its absolute value in a second sub-period different from the first sub-period.

2. The plasma processing apparatus according to claim 1, wherein the control unit controls the DC power supply such that the absolute value of the DC voltage when the bias power has a positive potential during the second period is greater than the absolute value of the DC voltage when the bias power has a negative potential during the second period.

3. The plasma processing apparatus according to claim 1, wherein the control unit controls the DC power supply such that the absolute value of the DC voltage when the bias power has a negative potential during the second period is greater than the absolute value of the DC voltage when the bias power has a positive potential during the second period.

4. The plasma processing apparatus according to any one of claims 1 to 3, wherein the control unit controls the high-frequency power supply and the bias power supply such that the supply of the high-frequency power and the supply of the bias power are stopped during a period between the first period and the second period.

5. The plasma processing apparatus according to claim 4, wherein the control unit controls the DC power supply to apply a DC voltage having an absolute value smaller than the minimum absolute value of the DC voltage applied to the upper electrode during the first sub-period and having a negative polarity to the upper electrode during the period between the first period and the second period.

6. The plasma processing apparatus according to any one of claims 1 to 5, wherein The control unit controls the DC power supply so as to apply a DC voltage having an absolute value smaller than the minimum absolute value of the DC voltage applied to the upper electrode during the first sub-period, and apply the DC voltage having a negative polarity to the upper electrode during the first period.

7. The plasma processing apparatus according to any one of claims 1 to 6, wherein, the level of the DC voltage applied to the upper electrode by the DC power supply during the first sub-period changes in such a manner as to maintain a constant potential difference between the upper electrode and the lower electrode.

8. The plasma processing apparatus according to any one of claims 1 to 7, wherein, the level of the DC voltage during the second sub-period is zero.

9. The plasma processing apparatus according to any one of claims 1 to 8, wherein, the bias power is a high-frequency bias power having the second frequency.

10. The plasma processing apparatus according to any one of claims 1 to 8, wherein, the bias power is a DC voltage, which is negative in polarity during one of two sub-periods within each period defined by the second frequency, and has a level of zero or is negative in polarity and has an absolute value smaller than its absolute value during the other sub-period during the other sub-period.

11. A plasma processing method using a plasma processing apparatus, the plasma processing apparatus comprising: a chamber; a substrate support having a lower electrode and configured to support a substrate within the chamber; an upper electrode disposed above the lower electrode; a high-frequency power supply configured to supply high-frequency power having a first frequency for generating plasma from a gas within the chamber; a bias power supply, which is a bias power supply electrically connected to the lower electrode and configured to supply a bias power for introducing ions to a substrate placed on the substrate support and changing the potential of the substrate placed on the substrate support within each period defined by a second frequency; and a DC power supply electrically connected to the upper electrode, the plasma processing method comprising: a step of supplying the high-frequency power during a first period; a step of setting the power level of the high-frequency power during a second period after the first period to a power level reduced from the power level of the high-frequency power during the first period; a step of applying the bias power to the lower electrode within the second period; and a step of applying a DC voltage from the DC power supply to the upper electrode within the second period, the DC voltage being set such that, within each period defined by the second frequency, it is negative in polarity during a first sub-period, and its absolute value during the first sub-period is greater than its absolute value during a second sub-period different from the first sub-period.

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