JP7535438B2 - Plasma processing apparatus and plasma processing method - Google Patents

Description

An exemplary embodiment of the present disclosure relates to a plasma processing apparatus and a plasma processing method.

A plasma processing apparatus is used for processing a substrate. One type of plasma processing apparatus includes a chamber, a mounting table, a first high frequency power supply, and a second high frequency power supply. The mounting table is configured to support a substrate in the chamber. The mounting table includes a lower electrode. The first high frequency power supply is configured to generate high frequency power for generating plasma from a gas in the chamber. The second high frequency power supply is configured to generate high frequency bias power for attracting ions from the plasma to the substrate. The high frequency bias power is supplied to the lower electrode. The following Patent Document 1 discloses a plasma processing apparatus configured to supply at least one of the high frequency power and the high frequency bias power as pulsed power.

JP 2016-157735 A

The present disclosure provides a technology that improves the uniformity of the radial density distribution of plasma and suppresses a decrease or loss of plasma density.

In one exemplary embodiment, a plasma processing apparatus is provided. The plasma processing apparatus includes a plasma processing chamber, a substrate support, a bias power supply, and a radio frequency power supply. The substrate support is disposed in the plasma processing chamber and includes an electrode. The bias power supply is coupled to the electrode and configured to generate a bias power having a first frequency. The radio frequency power supply is coupled to the plasma processing chamber and configured to generate a radio frequency power having a second frequency higher than the first frequency. The radio frequency power has a first power level during a first period within a cycle of the bias power and a second power level during a second period within a cycle of the bias power that is lower than the first power level.

According to one exemplary embodiment , it is possible to increase the uniformity of the radial density distribution of the plasma and suppress a decrease or disappearance of the plasma density.

1 is a schematic diagram of a plasma processing apparatus according to an exemplary embodiment; 4 is a timing chart of an example of high frequency power and electrical bias used in a plasma processing apparatus according to an exemplary embodiment. 5 is a timing chart of another example of high frequency power and electrical bias used in a plasma processing apparatus according to an exemplary embodiment. 6 is a timing chart of yet another example of an electrical bias used in a plasma processing apparatus according to an exemplary embodiment. FIG. 13 is a schematic diagram of a plasma processing apparatus according to another exemplary embodiment. 6 illustrates an example edge ring that can be used in the plasma processing apparatus illustrated in FIG. 5. FIG. 13 is a diagram showing another example of an edge ring. 1 is a flow diagram of a plasma processing method according to an exemplary embodiment.

Various exemplary embodiments are described below.

In one exemplary embodiment, a plasma processing apparatus is provided. The plasma processing apparatus includes a plasma processing chamber, a substrate support, a bias power supply, and a radio frequency (RF) power supply. The substrate support is disposed in the plasma processing chamber and includes a lower electrode. The bias power supply is coupled to the lower electrode and configured to generate a bias power having a first frequency. The radio frequency power supply is coupled to the plasma processing chamber and configured to generate a radio frequency power having a second frequency higher than the first frequency. In one embodiment, the radio frequency power supply is coupled to at least one of two opposing electrodes, such as an upper electrode and a lower electrode. The radio frequency power has a first power level during a first period within one period of the bias power, and has a second power level lower than the first power level during a second period within one period of the bias power. One period of the bias power is a natural period defined by the first frequency. That is, the natural period is the reciprocal of the first frequency. For example, if the first frequency is 400 kHz, the natural period is 2.5 μs. The first period is different from the second period. The second period may be before the first period or after the first period.

In one exemplary embodiment, the bias power includes at least one bias pulse within one period. The at least one bias pulse may have a pulse waveform that is rectangular, trapezoidal, triangular, or a combination thereof, and may include a shaped pulse (also called a tailored pulse) as disclosed in US 2018/0166249 A1. The at least one bias pulse has a positive or negative polarity. The at least one bias pulse may also include multiple bias pulses with positive and/or negative polarities. In one embodiment, the bias power includes at least one positive bias pulse and at least one negative bias pulse within one period.

In one exemplary embodiment, the bias power is a radio frequency bias power having a first frequency. In one embodiment, the bias power supply is configured to generate the radio frequency bias power continuously. In this case, the radio frequency bias power does not include an off period.

In another exemplary embodiment, a plasma processing apparatus is provided. The plasma processing apparatus includes a chamber, a substrate support, a bias power supply, and a radio frequency power supply. The substrate support includes a lower electrode and is configured to support a substrate in the chamber. The bias power supply is configured to generate an electrical bias for attracting ions to the substrate and is electrically connected to the lower electrode. The electrical bias varies the potential of the substrate within a period defined by a first frequency. The radio frequency power supply is configured to generate radio frequency power having a second frequency for generating plasma from a gas in the chamber. The radio frequency power supply is configured to provide a first pulse of radio frequency power in a first period and a second pulse of radio frequency power in a second period. The first period at least partially overlaps with the period defined by the first frequency and has a time length that is shorter than the time length of the period. The second period at least partially overlaps with the period defined by the first frequency and has a time length that is shorter than the time length of the period. The second pulse has a power level that is lower than the power level of the first pulse.

When high frequency power is supplied continuously, i.e., when a continuous wave of high frequency power is supplied, the density of the plasma in the chamber is high in the center and low on the radially outer side. In the above embodiment, the high frequency power is supplied as a first pulse. Therefore, according to the above embodiment, the uniformity of the radial density distribution of the plasma is increased. Also, in the above embodiment, after the supply of the first pulse, a second pulse of high frequency power having a relatively low power is supplied. Therefore, according to the above embodiment, it is possible to suppress a decrease or disappearance of the plasma density.

In one exemplary embodiment, the electrical bias may be a pulse wave that is periodically generated with a period defined by a first frequency. The pulse wave includes pulses of a negative DC voltage.

In one exemplary embodiment, each of the first period and the second period may be a period during which no pulse of negative DC voltage is supplied from the bias power supply within a period defined by the first frequency. According to this embodiment, reflections of each of the first pulse and the second pulse are reduced.

In one exemplary embodiment, the radio frequency power source may be configured to provide radio frequency power having a power level lower than the power level of the first pulse and the power level of the second pulse and greater than 0 W during a period between the first and second periods.

In one exemplary embodiment, the first period may overlap a period during which a pulse of negative DC voltage is provided from the bias power supply. The second period may be a period during which a pulse of negative DC voltage is not provided from the bias power supply within the cycle.

In one exemplary embodiment, the high frequency power source may be configured to supply high frequency power during a period between a second period within a cycle defined by the first frequency and an end point of the cycle. The high frequency power supplied during the period between the second period and the end point of the cycle has a power level that is lower than the power level of the first pulse and the power level of the second pulse and is greater than 0 W.

In one exemplary embodiment, the electrical bias may be a radio frequency bias power having a first frequency.

In one exemplary embodiment, the plasma processing apparatus may further include a matching box connected between the bias power supply and the lower electrode. The first pulse and the second pulse may be supplied when the impedance of the load relative to the bias power supply is approximately matched.

In yet another exemplary embodiment, a plasma processing method is provided. The plasma processing method includes preparing a substrate on a substrate support provided in a chamber of a plasma processing apparatus. The plasma processing apparatus includes a bias power supply and a high frequency power supply. The bias power supply is configured to generate an electric bias that varies the potential of the substrate within a period defined by a first frequency. The high frequency power supply is configured to generate high frequency power having a second frequency. The plasma processing method includes supplying an electric bias from the bias power supply to a lower electrode of the substrate support. The plasma processing method further includes supplying a first pulse of high frequency power from the high frequency power supply in a first period. The first period at least partially overlaps with the period defined by the first frequency and has a time length shorter than the time length of the period. The plasma processing method further includes supplying a second pulse of high frequency power from the high frequency power supply in a second period within the period defined by the first frequency. The second period at least partially overlaps with the period defined by the first frequency and has a time length shorter than the time length of the period. The second pulse has a power level that is lower than the power level of the first pulse.

Various exemplary embodiments will be described in detail below with reference to the drawings. Note that the same or equivalent parts in each drawing will be given the same reference numerals.

1 is a schematic diagram of a plasma processing apparatus according to an exemplary embodiment. The plasma processing apparatus 1 shown in FIG. 1 is a capacitively coupled plasma processing apparatus. The plasma processing apparatus 1 includes a plasma processing chamber 10. The chamber 10 provides an internal space 10s therein. The central axis of the internal space 10s is an axis AX extending in the vertical direction. 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. A plasma-resistant film is formed on the inner wall surface of the chamber body 12, i.e., the wall surface defining the internal space 10s. This film may be a ceramic film, such as a film formed by anodizing or a film formed from yttrium oxide.

A passage 12p is formed in the sidewall of the chamber body 12. The substrate W passes through the passage 12p when it is transported between the internal space 10s and the outside of the chamber 10. A gate valve 12g is provided along the sidewall of the chamber body 12 to open and close this passage 12p.

The plasma processing apparatus 1 further includes a substrate support 16. The substrate support 16 is configured to support a substrate W placed thereon in the chamber 10. The substrate W has a substantially disk-like shape. The substrate support 16 is supported by a support portion 17. The support portion 17 extends upward from the bottom of the chamber body 12. The support portion 17 has a substantially cylindrical shape. The support portion 17 is formed from an insulating material such as quartz.

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 made of a conductive material such as aluminum and has a generally disk-like shape.

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., freon) that cools the lower electrode 18 by vaporizing is used. A heat exchange medium supply device (e.g., a chiller unit) is connected to the flow path 18f. This supply device is provided outside the chamber 10. The heat exchange medium is supplied to the flow path 18f from the supply device via the pipe 23a. The heat exchange medium supplied to the flow path 18f is returned to the supply device via the pipe 23b.

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

The electrostatic chuck 20 has a body and an electrode. The body of the electrostatic chuck 20 is formed from a dielectric material such as aluminum oxide or aluminum nitride. The body of the electrostatic chuck 20 has a substantially disk shape. The central axis of the electrostatic chuck 20 substantially coincides with the axis AX. The electrode of the electrostatic chuck 20 is provided within the 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 attractive force is generated between the electrostatic chuck 20 and the substrate W. The generated electrostatic attractive force attracts the substrate W to the electrostatic chuck 20 and the substrate W is held by the electrostatic chuck 20.

The electrostatic chuck 20 includes a substrate mounting area. The substrate mounting area is a region having a substantially disk shape. The central axis of the substrate mounting area substantially coincides with the axis AX. When the substrate W is processed in the chamber 10, it is placed on the upper surface of the substrate mounting area.

In one embodiment, the electrostatic chuck 20 may further include an edge ring mounting region. The edge ring mounting region extends in a circumferential direction around the central axis of the electrostatic chuck 20 to surround the substrate mounting region. An edge ring ER is mounted on the upper surface of the edge ring mounting region. The edge ring ER has an annular shape. The edge ring ER is mounted on the edge ring mounting region so that its central axis coincides with the axis AX. The substrate W is disposed within the region surrounded by the edge ring ER. That is, the edge ring ER is disposed to surround the edge of the substrate W. The edge ring ER may be conductive. The edge ring ER is formed of, for example, silicon or silicon carbide. The edge ring ER may be formed of a dielectric material such as quartz.

The plasma processing apparatus 1 may further include a gas supply line 25. The gas supply line 25 supplies a heat transfer gas, such as He gas, from a gas supply mechanism to the gap between the upper surface of the electrostatic chuck 20 and the rear surface (lower surface) of the substrate W.

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 circumferential surface of the lower electrode 18. The insulating region 27 is formed from an insulator such as quartz. The edge ring ER is mounted on the insulating region 27 and the edge ring mounting region.

The plasma processing apparatus 1 further includes an upper electrode 30. The upper electrode 30 is provided above the substrate support 16. That is, the upper electrode 30 is provided above the lower electrode 18. The upper electrode 30 closes the upper opening of the chamber body 12 together with a member 32. The member 32 has insulating properties. The upper electrode 30 is supported on the upper part of the chamber body 12 via this member 32.

The upper electrode 30 includes a top plate 34 and a support 36. The bottom surface of the top plate 34 defines an internal space 10s. A plurality of gas discharge holes 34a are formed in the top plate 34. Each of the plurality of gas discharge holes 34a penetrates the top plate 34 in the plate thickness direction (vertical direction). The top plate 34 is made of, but is not limited to, silicon, for example. Alternatively, the top plate 34 may have a structure in which a plasma-resistant film is provided on the surface of an aluminum member. This film may be a ceramic film, such as a film formed by anodizing or a film formed from yttrium oxide.

The support 36 supports the top plate 34 in a removable manner. The support 36 is made of a conductive material such as aluminum. A gas diffusion chamber 36a is provided inside the support 36. A plurality of gas holes 36b extend downward from the gas diffusion chamber 36a. The plurality of gas holes 36b are connected to the plurality of gas discharge holes 34a. A gas introduction port 36c is formed in the support 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.

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

A baffle plate 48 is provided between the substrate support 16 or the support portion 17 and the side wall of the chamber body 12. The baffle plate 48 can be constructed, for example, by coating an aluminum member with a ceramic such as yttrium oxide. This baffle plate 48 has a large number of through holes. Below the baffle plate 48, an exhaust pipe 52 is connected to the bottom of the chamber body 12. This exhaust pipe 52 is connected to an exhaust device 50. 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.

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 second frequency. The second frequency is a frequency in the range of 13 to 200 MHz, for example, a frequency of 40 MHz or 60 MHz. The high-frequency power supply 61 is connected to the lower electrode 18 via a matching circuit 63 in order to supply the high-frequency power RF to the lower electrode 18. The matching circuit 63 is configured to match the impedance of the load side (lower electrode 18 side) of the high-frequency power supply 61 to the output impedance of the high-frequency power supply 61. Note that the high-frequency power supply 61 does not have to be electrically connected to the lower electrode 18, and may be connected to the upper electrode 30 via the matching circuit 63.

The plasma processing apparatus 1 further includes a bias power supply 62. The bias power supply 62 is connected to the lower electrode 18 via a circuit 64. The bias power supply 62 generates an electric bias (bias power) EB. The electric bias EB is used to attract ions to the substrate W. The electric bias EB is set to vary the potential of the substrate W placed on the electrostatic chuck 20 within a period CP defined by a first frequency. The period CP is the reciprocal of the first frequency. The first frequency can be a frequency lower than the second frequency. The first frequency is, for example, a frequency not less than 50 kHz and not more than 27 MHz.

2 is a timing chart of an example of high frequency power and an electric bias used in a plasma processing apparatus according to an exemplary embodiment. FIG. 3 is a timing chart of another example of high frequency power and an electric bias used in a plasma processing apparatus according to an exemplary embodiment. In one embodiment, as shown in FIG. 2 or FIG. 3, a pulse wave PLW is used as the electric bias EB. When the pulse wave PLW is used as the electric bias EB, the circuit 64 includes a filter circuit that blocks or reduces the high frequency power RF. The pulse wave PLW is applied to the lower electrode 18 periodically with a pulse period CP. The pulse wave PLW includes at least one bias pulse. In one embodiment, the pulse wave PLW includes a negative DC voltage pulse NPL. The pulse NPL is also applied to the lower electrode 18 periodically with a period CP. The pulse NPL is applied to the lower electrode 18 in a period PA within the period CP. In a period PB other than the period PA within the period CP, the voltage level of the pulse wave PLW may be 0V. Alternatively, the voltage level of the pulse wave PLW may have an absolute value smaller than the absolute value of the voltage of the pulse NPL during the period PB. Also, the voltage level of the pulse wave PLW may have a positive value smaller than the voltage value of the pulse NPL during the period PB. Note that the start timing and duration of the period CP, the voltage level of the pulse wave PLW, and the proportion of the period PA in the period CP (i.e., the duty ratio) can be specified to the bias power supply 62 by a control signal from the control unit MC, which will be described later.

When plasma etching is performed in the plasma processing apparatus 1, gas is supplied to the internal space 10s. Then, high-frequency power RF is supplied, and the gas is excited in the internal space 10s. Also, an electric bias EB is applied to the lower electrode 18, and ions from the plasma are attracted to the substrate W. Then, the substrate W is processed by chemical species such as ions and/or radicals from the plasma. For example, plasma etching of the substrate W is performed.

In the plasma processing apparatus 1, the high frequency power supply 61 supplies a first pulse RFP1 of high frequency power RF in a first period P1 as shown in FIG. 2 or FIG. 3. The first period P1 has a time length shorter than the time length of the period CP and at least partially overlaps with the period CP. The high frequency power supply 61 also supplies a second pulse RFP2 of high frequency power RF in a second period P2. The second period P2 is a period separate from the first period P1. The second period P2 has a time length shorter than the time length of the period CP and at least partially overlaps with the period CP. The power level (second power level) of the second pulse RFP2 is lower than the power level (first power level) of the first pulse RFP1. The first period P1 and the second period P2, as well as the power level of the high frequency power RF, can be specified for the high frequency power supply 61 by a control signal from the control unit MC. The power level of the radio frequency power RF that can be specified for the radio frequency power source 61 includes the power level of the first pulse RFP1 and the power level of the second pulse RFP2.

In one embodiment, as shown in FIG. 2, each of the first period P1 and the second period P2 is a period within the period (i.e., the period PB) in which the pulse NPL is not supplied within the cycle CP. In the period PB, the thickness of the sheath (plasma sheath) becomes thinner and the impedance becomes smaller. Therefore, reflection of each of the first pulse RFP1 and the second pulse RFP2 is suppressed. In this embodiment, as shown in FIG. 2, the high frequency power supply 61 may be configured to supply high frequency power RF in a third period P3 between the first period P1 and the second period P2. The power level of the high frequency power RF supplied in the period P3 between the period P1 and the period P2 may have a third power level that is lower than the power level of the first pulse RFP1 and the power level of the second pulse RFP2 and is greater than 0 W. Note that in this embodiment, the power level of the high frequency power RF in the period PA may be 0 W. Alternatively, the power level of the radio frequency power RF in period PA may be greater than 0 W and lower than the power level of the first pulse, the power level of the second pulse, and the power level of the radio frequency power RF in period P3.

In one embodiment, as shown in FIG. 3, the first period P1 overlaps with the period PA during which the pulse NPL is supplied. In this embodiment, the second period P2 is a period during which the pulse NPL is not supplied within the period CP (i.e., the period PB). In this embodiment, as shown in FIG. 3, the high frequency power supply 61 may be configured to supply high frequency power RF in a fourth period P4 between the second period P2 and the end point of the period CP including the second period P2 (or the start point of the next period CP). The power level of the high frequency power RF supplied in the period P4 after the period P2 may have a fourth power level that is lower than the power level of the first pulse RFP1 and the power level of the second pulse RFP2 and is greater than 0 W. Note that in this embodiment, the power level of the high frequency power RF in the period between the first period P1 and the second period P2 may be 0 W. Alternatively, the power level of the radio frequency power RF in the period between the first period P1 and the second period P2 may be greater than 0 W and lower than the power level of the first pulse, the power level of the second pulse, and the power level of the radio frequency power RF in period P4.

In one embodiment, the plasma processing apparatus 1 may further include a sheath adjuster 74 as shown in FIG. 1. The sheath adjuster 74 is configured to adjust the position of the upper end of the sheath above the edge ring ER in order to vertically correct the direction of travel of ions from the plasma relative to the edge of the substrate W. The sheath adjuster 74 adjusts the position of the upper end of the sheath above the edge ring ER so as to eliminate or reduce the difference between the position of the upper end of the sheath above the edge ring ER and the position of the upper end of the sheath above the substrate W.

In one embodiment, the sheath adjuster 74 is a power supply configured to apply a voltage _VN to the edge ring ER. The voltage _VN may be a negative voltage. Note that the voltage _VN may have the same waveform as the electrical bias EB. In this embodiment, the sheath adjuster 74 is connected to the edge ring ER via a filter 75 and a conductor 76. The filter 75 is a filter for blocking or reducing high frequency power flowing into the sheath adjuster 74.

The level of the voltage _VN determines the amount of adjustment of the upper end position of the sheath above the edge ring ER. The amount of adjustment of the upper end position of the sheath above the edge ring ER, i.e., the level of the voltage _VN , is determined according to a parameter representing the thickness of the edge ring ER. This parameter may be a measured value of the thickness of the edge ring ER measured optically or electrically, a vertical position of the upper surface of the edge ring ER measured optically or electrically, or a time length during which the edge ring ER is exposed to plasma. The level of the voltage _VN is determined using a predetermined relationship between such a parameter and the level of the voltage _VN . For example, the predetermined relationship between the parameter and the level of the voltage _VN is predetermined so that the absolute value of the voltage _VN increases as the thickness of the edge ring ER decreases. This relationship is stored in a storage device of the control unit MC, which will be described later, as data in the form of a function or table. The level of the voltage _VN is determined by the control unit MC and specified for the sheath adjuster 74. When a voltage _VN having a determined level is applied to the edge ring ER by the sheath adjuster 74, the difference between the position of the top end of the sheath above the edge ring ER and the position of the top end of the sheath above the substrate W is eliminated or reduced.

The voltage applied to the edge ring ER by the sheath adjuster 74 may be a DC voltage or a radio frequency voltage. The voltage applied to the edge ring ER may be a voltage having the same waveform as the electric bias EB. The voltage applied to the edge ring ER by the sheath adjuster 74 may be a pulsed radio frequency voltage or a pulsed DC voltage. That is, the voltage _VN may be applied to the edge ring ER periodically. The voltage _VN may be applied to the edge ring ER, for example, in a period PA within the period CP or in a period overlapping with the period PA. When a pulsed DC voltage is applied to the edge ring ER periodically as the voltage _VN , the level of the voltage _VN may change during the period during which the voltage _VN is applied to the edge ring ER.

The control unit MC is a computer equipped with 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 based on recipe data stored in the storage device. Under the control of the control unit MC, a process specified by the recipe data is executed in the plasma processing apparatus 1. A plasma processing method according to an exemplary embodiment described below can be executed in the plasma processing apparatus 1 under the control of each part of the plasma processing apparatus 1 by the control unit MC.

When high frequency power RF is supplied continuously, i.e., when a continuous wave of high frequency power RF is supplied, the density of the plasma in the chamber 10 is high at the center (i.e., at the position on the axis AX and its vicinity) and low on the radially outer side. In the plasma processing apparatus 1, the high frequency power RF is supplied as a first pulse RFP1. Therefore, according to the plasma processing apparatus 1, the uniformity of the radial density distribution of the plasma is increased. In addition, in the plasma processing apparatus 1, after the supply of the first pulse RFP1, a second pulse RFP2 of high frequency power RF having a relatively low power is supplied. Therefore, according to the plasma processing apparatus 1, it is possible to suppress a decrease or disappearance of the plasma density.

Reference is now made to FIG. 4. FIG. 4 is a timing chart of yet another example of an electric bias used in a plasma processing apparatus according to an exemplary embodiment. As shown in FIG. 4, the bias power supply 62 of the plasma processing apparatus 1 may supply radio frequency (RF) bias power to the lower electrode 18 as the electric bias EB. The RF bias power has the first frequency described above. In this embodiment, the circuit 64 is a matching circuit and is configured to match the impedance of the load side (lower electrode 18 side) of the bias power supply 62 with the output impedance of the bias power supply 62.

When high frequency bias power is used as the electric bias EB, each of the first pulse RFP1 and the second pulse RFP2 can be supplied when the impedance of the load for the bias power supply 62 is approximately matched. That is, each of the first period P1 and the second period P2 can overlap with a period in the period CP during which the impedance of the load for the bias power supply 62 is approximately matched to the output impedance of the bias power supply 62. The load for the bias power supply 62 includes the plasma generated in the chamber 10.

Reference will now be made to Figures 5 and 6. Figure 5 is a schematic diagram of a plasma processing apparatus according to another exemplary embodiment. Figure 6 is a diagram showing an example of an edge ring that can be used in the plasma processing apparatus shown in Figure 5. The plasma processing apparatus 1B shown in Figure 5 differs from the plasma processing apparatus 1 in that it uses an edge ring ERB instead of an edge ring ER. The plasma processing apparatus 1B also differs from the plasma processing apparatus 1 in that it includes a sheath adjuster 74B instead of a sheath adjuster 74. In other respects, the configuration of the plasma processing apparatus 1B may be the same as the configuration of the plasma processing apparatus 1.

As shown in FIG. 6, the edge ring ERB has a first annular portion ER1 and a second annular portion ER2. The first annular portion ER1 and the second annular portion ER2 are separated from each other. The first annular portion ER1 is annular and plate-shaped, and is placed on the edge ring mounting area so as to extend around the axis AX. The substrate W is placed on the substrate mounting area so that its edge is located on or above the first annular portion ER1. The second annular portion ER2 is annular and plate-shaped, and is placed on the edge ring mounting area so as to extend around the axis AX. The second annular portion ER2 is located radially outside the first annular portion ER1.

The sheath adjuster 74B is configured to move the second annular portion ER2 upward to adjust the vertical position of the upper surface of the second annular portion ER2. In one example, the sheath adjuster 74B includes a drive unit 74a and a shaft 74b. The shaft 74b supports the second annular portion ER2 and extends downward from the second annular portion ER2. The drive unit 74a is configured to generate a drive force for moving the second annular portion ER2 along the vertical direction via the shaft 74b.

The sheath adjuster 74B is configured to adjust the amount of adjustment of the upper end position of the sheath above the edge ring ERB, i.e., the vertical position of the upper surface of the second annular member ER2, in order to vertically correct the direction of travel of ions from the plasma relative to the edge of the substrate W. The sheath adjuster 74B moves the second annular member ER2 vertically so that the vertical position of the upper surface of the second annular member ER2 coincides with the vertical position of the upper surface of the substrate W on the electrostatic chuck 20.

The adjustment amount of the top end position of the sheath above the edge ring ERB, i.e., the movement amount of the second annular portion ER2, is determined according to a parameter reflecting the thickness of the edge ring ERB, i.e., the thickness of the second annular portion ER2. This parameter can be a measured value of the thickness of the second annular portion ER2 measured optically or electrically, a vertical position of the top surface of the second annular portion ER2 measured optically or electrically, or the length of time the edge ring ERB is exposed to plasma. The movement amount of the second annular portion ER2 is determined using a predetermined relationship between such a parameter and the movement amount of the second annular portion ER2. For example, the predetermined relationship between the parameter and the movement amount of the second annular portion ER2 is predetermined such that the movement amount of the second annular portion ER2 increases as the thickness of the second annular portion ER2 decreases. When the second annular portion ER2 is moved upward by the determined movement amount, the difference between the top end position of the sheath on the edge ring ERB and the top end position of the sheath above the substrate W is eliminated or reduced.

In the plasma processing apparatus 1B, the control unit MC can determine the movement amount of the second annular portion ER2 as described above. The predetermined relationship between the above-mentioned parameters and the movement amount of the second annular portion ER2 can be stored in the storage device of the control unit MC as function or table-format data. The control unit MC can control the sheath adjuster 74B to move the second annular portion ER2 upward by the determined movement amount.

Figure 7 is a diagram showing another example of an edge ring. In the edge ring ERB shown in Figure 7, the first annular portion ER1 has an inner peripheral portion and an outer peripheral portion. The vertical position of the upper surface of the inner peripheral portion is lower than the vertical height position of the upper surface of the outer peripheral portion. The substrate W is placed on the substrate placement area so that its edge is located on the inner peripheral portion of the first annular portion ER1. The second annular portion ER2 is placed on the inner peripheral portion of the first annular portion ER1 so as to surround the edge of the substrate W. That is, in the edge ring ERB shown in Figure 7, the second annular portion ER2 is placed inside the outer peripheral portion of the first annular portion ER1. When the edge ring ERB shown in Figure 7 is used, the shaft 74b of the sheath adjuster 74B can reach the lower surface of the second annular portion ER2 through a through hole formed in the inner peripheral portion of the first annular portion ER1.

Refer to FIG. 8 below. FIG. 8 is a flow chart of a plasma processing method according to one exemplary embodiment. The plasma processing method shown in FIG. 8 (hereinafter, referred to as "method MT") is performed using any of the plasma processing apparatuses according to various embodiments, such as the plasma processing apparatus 1 and plasma processing apparatus 1B described above.

Method MT begins with step ST1. In step ST1, a substrate W is prepared in the chamber 10. In the chamber 10, the substrate W is placed on the electrostatic chuck 20. Steps ST2, ST3, and ST4 of method MT are performed with the substrate W placed on the electrostatic chuck 20. In method MT, gas is supplied from a gas supply unit into the chamber 10. Then, the pressure in the chamber 10 is set to a specified pressure by the exhaust device 50.

In step ST2, an electrical bias EB is supplied to the lower electrode 18. In step ST3, a first pulse RFP1 of radio frequency power RF is supplied in a first period P1. In step ST4, a second pulse RFP2 of radio frequency power RF is supplied in a second period P2.

In step ST5, it is determined whether the termination condition is satisfied. The termination condition is satisfied when the number of repetitions of the cycle CP reaches a predetermined number. If it is determined in step ST5 that the termination condition is not satisfied, steps ST2, ST3, and ST4 are executed again. On the other hand, if it is determined in step ST5 that the termination condition is satisfied, the execution of method MT is terminated.

Although various exemplary embodiments have been described above, various additions, omissions, substitutions, and modifications may be made without being limited to the exemplary embodiments described above. In addition, elements in different embodiments may be combined to form other embodiments.

In another embodiment, the plasma processing apparatus may be an inductively coupled plasma processing apparatus, an ECR (electron cyclotron resonance) plasma processing apparatus, or a plasma processing apparatus that generates plasma using surface waves such as microwaves.

From the foregoing, it will be understood that the various embodiments of the present disclosure have been described herein for purposes of illustration, and that various modifications may be made without departing from the scope and spirit of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the appended claims.

1...plasma processing apparatus, 10...chamber, 16...substrate support, 18...lower electrode, 61...high frequency power supply, 62...bias power supply.

Claims (7)

a plasma processing chamber;
a substrate support disposed within the plasma processing chamber and including an electrode;
a bias power supply coupled to the electrode and configured to generate an electrical bias having a first voltage level during a first time period within a period and a second voltage level during a second time period within the period and a third time period after the second time period, the absolute value of the first voltage level being greater than the absolute value of the second voltage level;
a radio frequency power source coupled to the plasma processing chamber and configured to generate radio frequency power having a first power level during the first time period within the cycle, a second power level during the second time period within the cycle, a third power level during the third time period within the cycle, and a fourth power level during a fourth time period between the second and third time periods within the cycle, wherein the second power level is greater than the third power level, the third power level is greater than the first power level, and the fourth power level is between the first power level and the third power level;
A plasma processing apparatus comprising: The plasma processing apparatus of claim 1, wherein the electrical bias has a pulse waveform that is rectangular, trapezoidal, triangular, or a combination thereof. The plasma processing apparatus of claim 1, wherein the electrical bias has a shaped pulse. The plasma processing apparatus according to any one of claims 1 to 3, wherein the first voltage level has a negative polarity. The plasma processing apparatus according to any one of claims 1 to 4, wherein the second voltage level is a zero voltage level. The plasma processing apparatus according to any one of claims 1 to 5, wherein the first power level is a zero power level. A plasma processing method for use in a plasma processing apparatus, the plasma processing apparatus comprising: a plasma processing chamber; a substrate support disposed within the plasma processing chamber and including a lower electrode; and an upper electrode disposed above the lower electrode, the plasma processing method comprising the steps of:
placing a substrate on the substrate support;
providing an electrical bias to the lower electrode, the electrical bias having a first voltage level during a first time period within a period and a second voltage level during a second time period within the period and a third time period after the second time period, the absolute value of the first voltage level being greater than the absolute value of the second voltage level;
a step of supplying radio frequency power to the upper electrode or the lower electrode, the radio frequency power having a first power level in the first period within the one cycle, a second power level in the second period within the one cycle, a third power level in the third period within the one cycle, and a fourth power level in a fourth period between the second and third periods within the one cycle, the second power level being greater than the third power level, the third power level being greater than the first power level, and the fourth power level being a level between the first power level and the third power level;
A plasma processing method comprising:

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