Control method and plasma processing apparatus

Abstract

The present invention improves the control accuracy of an incident angle of ions incident on an edge region of a substrate.　Provided is a plasma processing device comprising: a substrate support unit that is disposed in a plasma processing chamber and supports a substrate; an edge ring disposed around the substrate supported by the substrate support unit; a lifter for moving up and down the edge ring; and a control unit. The control unit controls a step for preparing the substrate on the substrate support unit and processing the substrate by plasma, a step for measuring the wear amount of the edge ring, and a step for controlling the lifter so as to lower the edge ring on the basis of the wear amount of the edge ring.

Description

Control method and plasma processing apparatus

[0001] The present disclosure relates to a control method and a plasma processing apparatus.

[0002] For example, Japanese Patent Application Laid-Open No. 2006-144992 proposes a method for adjusting the height of the sheath by independently driving multiple lifter pins up and down to control the circumferential tilt of the edge ring, thereby eliminating variations in the etching rate and maintaining the vertical etching shape of the recesses.

[0003] Furthermore, Patent Document 2 proposes using a sheath adjuster to move the second annular portion upward in response to wear of the edge ring so that the vertical position of the upper surface of the second annular portion coincides with the vertical position of the upper surface of the substrate on the electrostatic chuck, thereby adjusting the vertical position of the upper end of the sheath above the edge ring and reducing the difference between the etching rate at the edge of the substrate and the etching rate inside the edge.

[0004] Furthermore, Patent Document 3 proposes moving the position of the edge ring from a first position to a second position higher than the first position in response to wear of the edge ring to make the edge ring parallel to the sheath on the substrate. Furthermore, Patent Document 4 proposes a movable edge ring for a substrate processing system with reduced fluctuations in capacitance.

[0005] Japanese Patent Application Publication No. 2019-201085 Japanese Patent Application Publication No. 2020-113753 U.S. Patent No. 11,393,710 International Publication No. 2021 / 026110

[0006] The present disclosure provides a control method and a plasma processing apparatus that improves the control accuracy of the angle of incidence of ions incident on the edge region of a substrate.

[0007] According to one aspect of the present disclosure, there is provided a plasma processing apparatus comprising: a substrate support disposed within a plasma processing chamber and supporting a substrate; an edge ring disposed around the substrate supported on the substrate support; a lifter for raising and lowering the edge ring; and a control unit, wherein the control unit controls the steps of preparing a substrate on the substrate support and processing the substrate with plasma; measuring the amount of wear of the edge ring; and controlling the lifter to lower the edge ring based on the amount of wear of the edge ring.

[0008] According to one aspect, it is possible to improve the accuracy of controlling the incident angle of ions incident on the edge region of the substrate.

[0009] FIG. 1 illustrates an example of a plasma processing system according to an embodiment. FIG. 2 illustrates a relationship between an ion incidence angle and a bias RF power frequency according to an example of edge ring operation. FIG. 3 illustrates a relationship between an ion incidence angle and a bias RF power frequency according to an example of edge ring operation. FIG. 4 illustrates a relationship between an ion incidence angle and a bias RF power frequency according to an example of edge ring operation. FIG. 5 illustrates a relationship between an ion incidence angle and a bias RF power frequency according to an example of edge ring operation. FIG. 6 illustrates a relationship between an ion incidence angle and a shape of the edge ring according to an example of edge ring operation. FIG. 7 illustrates a relationship between an ion incidence angle and a shape of the edge ring according to an example of edge ring operation. A flowchart illustrating an example of a method for controlling an edge ring according to an embodiment. FIG. 8 illustrates a method for controlling an edge ring according to an embodiment. FIG. 9 illustrates an example of an experimental result of the method for controlling an edge ring according to an embodiment. FIG. 10 illustrates an example of an experimental result of the method for controlling an edge ring according to an embodiment.

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant explanations may be omitted.

[0011] [Plasma Processing System] An example of the configuration of a plasma processing system will be described below. Fig. 1 is a diagram for explaining an example of the configuration of an inductively coupled plasma processing apparatus.

[0012] The plasma processing system includes an inductively coupled plasma processing apparatus 1 and a control unit 2. The inductively coupled plasma processing apparatus 1 includes a plasma processing chamber 10, a gas supply unit 20, a power supply 30, an exhaust system 40, and a lifter 50. The plasma processing chamber 10 includes a dielectric window. The plasma processing apparatus 1 also includes a substrate support 11, a gas inlet, and an antenna 14. The substrate support 11 is disposed within the plasma processing chamber 10. The antenna 14 is disposed on or above the plasma processing chamber 10 (i.e., on or above the dielectric window 101). The plasma processing chamber 10 has a plasma processing space 10s defined by the dielectric window 101, a sidewall 102 of the plasma processing chamber 10, and the substrate support 11. The plasma processing chamber 10 has at least one gas supply port for supplying at least one processing gas to the plasma processing space 10s and at least one gas exhaust port for exhausting gas from the plasma processing space 10s. The plasma processing chamber 10 is grounded.

[0013] The substrate support 11 includes a main body 111. The main body 111 has a central region 111a for supporting a substrate W and an annular region 111b for supporting a ring assembly 112. A wafer is an example of a substrate W. The annular region 111b of the main body 111 surrounds the central region 111a of the main body 111 in a plan view. The substrate W is disposed on the central region 111a of the main body 111. The ring assembly 112 is disposed on the annular region 111b of the main body 111 so as to surround the substrate W on the central region 111a of the main body 111. Therefore, the central region 111a is also called a substrate support surface for supporting the substrate W, and the annular region 111b is also called a ring support surface for supporting the ring assembly 112.

[0014] In one embodiment, the main body 111 includes a base 1110 and an electrostatic chuck 1111. The base 1110 includes a conductive member. The conductive member of the base 1110 can function as a bias electrode. The electrostatic chuck 1111 is disposed on the base 1110. The electrostatic chuck 1111 includes a ceramic member 1111a and an electrostatic electrode 1111b disposed within the ceramic member 1111a. The ceramic member 1111a has a central region 111a. In one embodiment, the ceramic member 1111a also has an annular region 111b. Note that the annular region 111b may also be provided by another member surrounding the electrostatic chuck 1111, such as an annular electrostatic chuck or an annular insulating member. In this case, the ring assembly 112 may be disposed on the annular electrostatic chuck or the annular insulating member, or may be disposed on both the electrostatic chuck 1111 and the annular insulating member. Furthermore, at least one RF / DC electrode coupled to an RF (Radio Frequency) power supply 31 and / or a DC (Direct Current) power supply 32 (described later) may be disposed within the ceramic member 1111a. In this case, the at least one RF / DC electrode functions as a bias electrode. Note that the conductive member of the base 1110 and the at least one RF / DC electrode may function as multiple bias electrodes. Alternatively, the electrostatic electrode 1111b may function as a bias electrode. Therefore, the substrate support 11 includes at least one bias electrode.

[0015] The ring assembly 112 includes one or more annular members. In one embodiment, the one or more annular members include one or more edge rings and at least one cover ring. The edge rings are formed of a conductive or insulating material, and the cover rings are formed of an insulating material.

[0016] In one embodiment, the ring assembly 112 includes a first ring 112a that can be raised and lowered, a second ring 112b that supports the first ring 112a, and a cover ring 113 (see FIGS. 5A and 5B). The first ring 112a is provided in a recess formed in the second ring 112b and can be raised and lowered. The raising and lowering of the first ring 112a changes the distance (gap D) between the first ring 112a and a bottom surface 112b1 of the recess formed in the second ring 112b. The first ring 112a is supported by the second ring 112b, and the inner peripheral surface of the first ring 112a surrounds the periphery of the substrate W. The outer peripheral surface of the first ring 112a is covered by the second ring 112b.

[0017] The first ring 112a and the second ring 112b may be made of SiC, Si, or quartz. The cover ring 113 may be made of quartz. In this specification, the first ring 112a and the second ring 112b are collectively referred to as edge rings. The edge ring is also referred to as a focus ring. However, the edge ring does not have to be divided into the first ring 112a and the second ring 112b, and may be configured as an integrated ring. The edge ring may also be divided into three or more parts.

[0018] Returning to FIG. 1 , the lifter 50 raises and lowers the first ring 112a. The lifter 50 includes a plurality of support pins 51 and an actuator 52. Although two support pins 51 are illustrated in FIG. 1 , three or more support pins 51 are provided. Each support pin 51 is formed in a cylindrical (solid) shape. Each support pin 51 is inserted through a through hole formed in the base 1110, a through hole formed in the electrostatic chuck 1111, and a through hole formed in the second ring 112b, and is capable of protruding and retracting relative to the bottom surface 112b1 of the recess in the second ring 112b (see FIGS. 5A and 5B ).

[0019] In the case of an integrated edge ring, each support pin 51 is inserted into a through hole formed in the base 1110 and a through hole formed in the electrostatic chuck 1111, and can protrude and retract into the ring support surface of the electrostatic chuck 1111.

[0020] The actuator 52 raises and lowers the plurality of support pins 51. The actuator 52 may be, for example, a motor such as a DC motor, a stepping motor, or a linear motor, an air-driven mechanism such as an air cylinder, or a piezoelectric actuator. The lifter 50 lowers the plurality of support pins 51 in accordance with the amount of wear of the first ring 112a, as will be described later.

[0021] The substrate support 11 may also include a temperature adjustment module configured to adjust at least one of the electrostatic chuck 1111, the ring assembly 112, and the substrate to a target temperature. The temperature adjustment module may include a heater, a heat transfer medium, a flow passage 1110a, or a combination thereof. A heat transfer fluid such as brine or a gas flows through the flow passage 1110a. In one embodiment, the flow passage 1110a is formed in the base 1110, and one or more heaters are disposed in the ceramic member 1111a of the electrostatic chuck 1111. The substrate support 11 may also include a heat transfer gas supply configured to supply a heat transfer gas to a gap between the backside of the substrate W and the central region 111a.

[0022] The gas inlet is configured to introduce at least one process gas from the gas supply unit 20 into the plasma processing space 10s. In one embodiment, the gas inlet includes a center gas injector (CGI) 13. The center gas injector 13 is disposed above the substrate support 11 and attached to a central opening formed in the dielectric window 101. The center gas injector 13 has at least one gas supply port 13a, at least one gas flow path 13b, and at least one gas inlet port 13c. The process gas supplied to the gas supply port 13a passes through the gas flow path 13b and is introduced into the plasma processing space 10s from the gas inlet port 13c. Note that the gas inlet may include one or more side gas injectors (SGIs) attached to one or more openings formed in the sidewall 102 in addition to or instead of the center gas injector 13.

[0023] The gas supply unit 20 may include at least one gas source 21 and at least one flow controller 22. In one embodiment, the gas supply unit 20 is configured to supply at least one process gas from a corresponding gas source 21 to the gas inlet through a corresponding flow controller 22. Each flow controller 22 may include, for example, a mass flow controller or a pressure-controlled flow controller. Additionally, the gas supply unit 20 may include one or more flow modulation devices to modulate or pulse the flow rate of the at least one process gas.

[0024] The power supply 30 includes an RF power supply 31 coupled to the plasma processing chamber 10 via at least one impedance matching circuit. The RF power supply 31 is configured to supply at least one RF signal (RF power) to at least one bias electrode and the antenna 14. This causes a plasma to be formed from at least one process gas supplied to the plasma processing space 10s. Therefore, the RF power supply 31 can function as at least a part of a plasma generating unit configured to generate a plasma from one or more process gases in the plasma processing chamber 10. Furthermore, by supplying a bias RF signal to the at least one bias electrode, a bias potential is generated on the substrate W, thereby attracting ions in the formed plasma to the substrate W.

[0025] In one embodiment, the RF power supply 31 includes a first RF generating unit 31a and a second RF generating unit 31b. The first RF generating unit 31a (source RF power supply) is coupled to the antenna 14 and configured to generate a source RF signal (source RF power) for plasma generation via at least one impedance matching circuit. In one embodiment, the source RF signal has a frequency in the range of 13 MHz to 150 MHz. However, it is preferable that the source RF signal (source RF power) have a frequency of 13 MHz or higher. In one embodiment, the first RF generating unit 31a may be configured to generate multiple source RF signals having different frequencies. The generated one or more source RF signals are supplied to the antenna 14.

[0026] The second RF generating unit 31b (bias RF power supply) is coupled to at least one bias electrode via at least one impedance matching circuit and configured to generate a bias RF signal (bias RF power). The frequency of the bias RF signal may be the same as or different from the frequency of the source RF signal. In one embodiment, the bias RF signal has a frequency lower than the frequency of the source RF signal. In one embodiment, the bias RF signal has a frequency in the range of 100 kHz to less than 13 MHz. However, it is preferable that the bias RF signal (bias RF power) has a frequency less than 13 MHz. In one embodiment, the second RF generating unit 31b may be configured to generate multiple bias RF signals having different frequencies. The generated one or more bias RF signals are supplied to at least one bias electrode. In various embodiments, at least one of the source RF signal and the bias RF signal may be pulsed.

[0027] The power supply 30 may also include a DC power supply 32 coupled to the plasma processing chamber 10. The DC power supply 32 includes a bias DC generator 32a. In one embodiment, the bias DC generator 32a is connected to at least one bias electrode and configured to generate a bias DC signal. The generated bias DC signal is applied to the at least one bias electrode.

[0028] In various embodiments, the bias DC signal may be pulsed. In this case, a sequence of voltage pulses is applied to at least one bias electrode. The voltage pulses may have a rectangular, trapezoidal, triangular, or combination thereof. In one embodiment, a waveform generator for generating the sequence of voltage pulses from the DC signal is connected between the bias DC generator 32a and at least one bias electrode. Thus, the bias DC generator 32a and the waveform generator constitute a voltage pulse generator. The voltage pulses may have positive or negative polarity. Furthermore, the sequence of voltage pulses may include one or more positive voltage pulses and one or more negative voltage pulses within one cycle. Note that the bias DC generator 32a may be provided in addition to the RF power supply 31 or may be provided instead of the second RF generator 31b.

[0029] The antenna 14 includes one or more coils. In one embodiment, the antenna 14 may include an outer coil and an inner coil arranged coaxially. In this case, the RF power supply 31 may be connected to both the outer coil and the inner coil, or to either the outer coil or the inner coil. In the former case, the same RF generator may be connected to both the outer coil and the inner coil, or separate RF generators may be connected to the outer coil and the inner coil separately.

[0030] The exhaust system 40 may be connected to, for example, a gas exhaust port 10e provided at the bottom of the plasma processing chamber 10. The exhaust system 40 may include a pressure regulating valve and a vacuum pump. The pressure in the plasma processing space 10s is regulated by the pressure regulating valve. The vacuum pump may include a turbomolecular pump, a dry pump, or a combination thereof.

[0031] The control unit 2 processes computer-executable instructions that cause the plasma processing apparatus 1 to perform various processes described in this disclosure. The control unit 2 may be configured to control each element of the plasma processing apparatus 1 to perform various processes described herein. In one embodiment, part or all of the control unit 2 may be included in the plasma processing apparatus 1. The control unit 2 may include a processing unit 2a1, a storage unit 2a2, and a communication interface 2a3. The control unit 2 may be implemented by, for example, a computer 2a. The processing unit 2a1 may be configured to read a program from the storage unit 2a2 and execute the read program to perform various control operations. This program may be stored in the storage unit 2a2 in advance or may be acquired via a medium when needed. The acquired program is stored in the storage unit 2a2 and read from the storage unit 2a2 by the processing unit 2a1 for execution. The medium may be various storage media readable by the computer 2a or a communication line connected to the communication interface 2a3. The processing unit 2a1 may be a CPU (Central Processing Unit). The storage unit 2a2 may include a random access memory (RAM), a read-only memory (ROM), a hard disk drive (HDD), a solid state drive (SSD), or a combination thereof. The communication interface 2a3 may communicate with the plasma processing apparatus 1 via a communication line such as a local area network (LAN).

[0032] [Ion Incident Angle] The edge rings (first ring 112a, second ring 112b) are exposed to plasma during processing of the substrate W and are worn away, resulting in a decrease in thickness. As the edge rings are worn away, the potential of the edge rings drops, and the height of the sheath above the edge rings becomes lower than the height of the sheath above the substrate W. This causes a phenomenon in which the angle of incidence of ions in the edge region of the substrate W is tilted inward (inner) in the radial direction of the substrate W with respect to the perpendicular direction of the substrate W due to a step in the sheath. The edge region of the substrate W is the outermost region of the substrate W, and, for example, is the region from the center of the substrate W to approximately 147 mm to 150 mm in the radial direction (to the outer peripheral edge of the substrate W).

[0033] By raising the height of the edge ring by an amount corresponding to the decrease in the height of the sheath due to wear of the edge ring, the height of the sheath on the edge ring can be increased, thereby controlling the inwardly tilted ion incident angle to tilt more outward (outer direction). This eliminates the tilt of the ion incident angle and allows ions to be incident perpendicularly onto the substrate W, thereby making it possible to make the etching shape vertical.

[0034] 2A to 2D are diagrams illustrating the relationship between the ion incident angle and the frequency of the bias RF power in an example of edge ring operation. For example, in FIGS. 2A and 2B, the first ring 112a is raised based on the amount of wear of the edge ring, thereby raising the height of the sheath S above the first ring 112a. This controls the ion incident angle in the edge region of the substrate W to tilt more outward (toward the outer side), as indicated by the arrow in FIG. 2B. Note that in this specification, the second ring 112b is fixed.

[0035] In the examples of Figures 2A and 2B, bias RF power having a frequency of 13 MHz is supplied to the substrate support 11 (base 1110). In contrast, in the examples of Figures 2C and 2D, bias RF power having a frequency of 400 kHz is supplied to the substrate support 11 (base 1110). In Figures 2A and 2C, the first ring 112a is in an initial state where it is not worn out, and is positioned at the lowest position. In Figures 2B and 2D, the first ring 112a is raised to the same height by the support pins 51.

[0036] A gap D is provided between the first ring 112a and the second ring 112b, preventing the first ring 112a and the second ring 112b from coming into contact with each other. The gap D is a gap formed between the bottom surface (lower surface 112a1), inner circumferential surface 112a2, and outer circumferential surface 112a3 of the first ring 112a as the first ring 112a moves up and down, and the inner surfaces (bottom surface 112b1, inner surface 112b2, and outer surface 112b3) of the recess formed in the second ring 112b. This prevents a sudden change in the potential of the first ring 112a due to contact between the first ring 112a and the second ring 112b, thereby avoiding an effect on the controllability (control accuracy) of the ion incident angle.

[0037] The impedance to the RF current due to the gap D varies depending on the frequency. When RF power with a frequency of 400 kHz is supplied, the impedance due to the gap D is greater than when RF power with a frequency of 13 MHz is supplied. As a result, the potential of the first ring 112a decreases relative to the potential of the second ring 112b. Furthermore, the larger the gap D, the lower the potential of the first ring 112a. As a result, when bias RF power of 400 kHz is supplied, the amount of change in the potential of the first ring 112a when the first ring 112a is raised and lowered is greater than when bias RF power of 13 MHz is supplied. The more the first ring 112a is raised, the larger the gap D, and the further the potential of the first ring 112a decreases. The larger the potential difference between the plasma and the first ring 112a, the thicker the sheath. Therefore, when the plasma is considered as ground, the lower the potential of the first ring 112a, the smaller the potential difference between the plasma and the first ring 112a, and the thinner the sheath. Therefore, the more the first ring 112a is raised, the more the sheath falls above the first ring 112a, and the ions are incident at an inclination inward (inner direction).

[0038] For example, in FIG. 2A , the potential of the second ring 112b is set to a "high" level. When 13 MHz bias RF power is supplied, the impedance due to the gap D is small, and the potential difference between the first ring 112a and the second ring 112b is small, so the potential of the first ring 112a is at a "high" level in FIG. 2A . When the first ring 112a is raised, the gap D increases, but with high-frequency bias RF power of about 13 MHz, the change in the potential of the first ring 112a is small, and the potential of the first ring 112a in FIG. 2B is at a "high" level. Therefore, in the state of FIG. 2B , the potential difference between the plasma and the first ring 112a is large, just like in the initial state of FIG. 2A . As described above, the thickness of the sheath is determined by the potential difference between the plasma and the edge ring; the larger the potential difference between the plasma and the edge ring, the thicker the sheath. Therefore, when bias RF power of 13 MHz is supplied, the thickness of the sheath remains almost unchanged even when the first ring 112a is raised and lowered, and the height of the sheath increases according to the height of the first ring 112a (the height position of the upper surface of the first ring 112a). As a result, when bias RF power of 13 MHz is supplied, the more the first ring 112a is raised, the more ions are incident on the edge region of the substrate W at an outward tilt, as shown by the arrow in FIG.

[0039] In contrast, when 400 kHz bias RF power is supplied, the impedance due to the gap D is large. Therefore, if the potential of the second ring 112b is set to a "high" level in the initial state of FIG. 2C , the potential of the first ring 112a drops to, for example, a "medium" level. When the first ring 112a is raised, the impedance due to the gap D further increases, and the amount of change in the potential of the first ring 112a is large, so the potential of the first ring 112a drops further when the first ring 112a is raised. The potential of the first ring 112a shown in FIG. 2D is, for example, at a "low" level.

[0040] Therefore, when the plasma is regarded as ground, the higher the first ring 112a is raised, the smaller the potential difference between the plasma and the first ring 112a, and the thinner the sheath becomes. That is, as a result of raising the first ring 112a, the reduction in the thickness of the sheath directly above the first ring 112a is greater than the amount by which the upper surface of the first ring 112a is raised, and therefore the height position of the sheath S directly above the first ring 112a becomes lower. As a result, when 400 kHz bias RF power is supplied, the higher the first ring 112a is raised, the more ions are incident on the edge region of the substrate W at an inward tilt, as shown by the arrow in FIG. 2D .

[0041] Therefore, when supplying 400 kHz bias RF power, one method is to lift the first ring 112a and the second ring 112b to the same potential or to reduce the potential difference before and after lifting in order to control the ion incident angle further outward by lifting the first ring 112a.

[0042] 3A and 3B are diagrams illustrating the relationship between the ion incidence angle and the edge ring shape in an example of edge ring operation. When supplying 400 kHz bias RF power, the shape of the second ring 112b is optimized so that the capacitance between the first ring 112a and the second ring 112b' is constant. This allows the first ring 112a and the second ring 112b to be at the same potential or have a small potential difference before and after lifting. As the first ring 112a is lifted, the ions are incident at an outward tilt, making it possible to control the ion incidence angle by lifting the first ring 112a. However, in this case, the shape of the second ring 112b' must be machined into a specialized shape that maintains a constant capacitance between the first ring 112a and the second ring 112b', which increases the number of parts and complicates the edge ring structure.

[0043] Furthermore, when etching deep holes, it is important to obtain a high-speed, vertical etching profile even in the edge region of the substrate W. That is, it is important to control the ion incident angle at the edge region to be vertical and to use ions with high ion energy to perform etching at a high etching rate. For example, when the vertical direction of the substrate W is 90 degrees, it is preferable to control the ion incident angle in the radial direction within a range of less than ±0.2 degrees, i.e., within a range of 89.8 degrees to 90.2 degrees.

[0044] Compared to RF power with a frequency of 13 MHz, RF power with a low frequency such as 400 kHz allows etching with high ion energy, and enables the processing of deep holes with high speed and vertical etching shapes.

[0045] However, plasma etching using RF power with a low frequency, such as 400 kHz, wears the edge ring quickly, and the angle of incidence of ions in the edge region of the substrate W tends to tilt inward. In addition, the life of the edge ring tends to be shortened, and the replacement cycle of the edge ring tends to become shorter.

[0046] Therefore, in one embodiment, the edge ring is divided into two parts, an upper part and an lower part, and the upper part, the first ring 112a, which is the divided edge ring and is arranged around the substrate W, is moved up and down using the lifter 50. The lower part, the second ring 112b, is fixed. In this way, when the edge ring is worn out during plasma etching using low-frequency RF power such as 400 kHz, only the first ring 112a needs to be replaced, thereby reducing costs.

[0047] [Edge Ring Control Method] In one embodiment of the edge ring control method, when bias RF power having a frequency of 13 MHz or higher is supplied to the substrate support 11, the first ring 112a is controlled to be lifted in response to the inward tilt of the ion incident angle based on the wear amount of the first ring 112a. This allows the ion incident angle to be controlled so that it shifts from an inward state to a more outward state (see FIG. 2B ). This allows the edge ring replacement cycle to be extended. Note that when bias RF power having a frequency of 13 MHz or higher is supplied to the substrate support 11, the initial position of the first ring 112a is the lowest position of the first ring 112a, as shown in FIG. 2A .

[0048] On the other hand, when bias RF power with a frequency of 400 kHz is supplied, the incident angle of ions tilts inward based on the wear of the first ring 112a, and if the first ring 112a is controlled to be raised, the incident angle of ions tilts further inward (see FIG. 2D ). Therefore, the incident angle of ions cannot be controlled to be approximately vertical.

[0049] Therefore, in one embodiment, when bias RF power with a frequency of 400 kHz is supplied, the edge ring control method controls the first ring 112a to lower in response to the ion incident angle tilting more inward based on the wear of the first ring 112a. This allows the ion incident angle to be controlled from an inward tilted state to a more outward tilted state. Therefore, by controlling the lowering position of the first ring 112a, the ion incident angle can be controlled to be approximately vertical. This allows the edge ring replacement cycle to be extended.

[0050] A method for controlling the edge ring divided into the first ring 112a and the second ring 112b will be described below with reference to FIG. 4 and FIGS. 5A and 5B. FIG. 4 is a flowchart illustrating an example of a method for controlling the edge ring according to an embodiment when bias RF power with a frequency of 400 kHz is supplied to the substrate support part 11. FIGS. 5A and 5B are diagrams for explaining a method for controlling the edge ring according to an embodiment when bias RF power with a frequency of 400 kHz is supplied to the substrate support part 11. Note that when bias RF power with a frequency of 13 MHz or higher is supplied to the substrate support part 11, the control part 2 controls the edge ring to be lifted based on the amount of wear of the first ring 112a, as shown in FIG. 2A(b).

[0051] The edge ring control method according to one embodiment, shown in FIG. 4 , is controlled by the controller 2 and executed by the plasma processing apparatus 1. In the plasma processing apparatus 1, the first ring 112a is exposed to plasma and wears out during plasma processing of the substrate W. The first ring 112a is placed at a position (initial position) elevated by a predetermined height from the surface facing the first ring 112a. As shown in FIG. 5A , in the initial state, the first ring 112a is elevated to its highest height by the support pins 51. That is, the initial position of the first ring 112a is set to the highest height of the first ring 112a at which the incident angle of ions at the edge region of the substrate W is controlled to be approximately perpendicular. In the edge ring control method according to one embodiment, the first ring 112a starts to descend from this initial position. Note that the surface facing the first ring 112a is the bottom surface 112b1 of the recess of the second ring 112b shown in FIGS. 5A and 5B . If the edge ring is not divided, the surface that the edge ring faces is the ring support surface of the electrostatic chuck 1111 .

[0052] When this process starts, in step S1, the control unit 2 measures the wear amount of the first ring 112a. During the processing of substrates W, the first ring 112a is worn by plasma. The control unit 2 can measure the wear amount of the first ring 112a directly or indirectly. As an example of a measurement method, the control unit 2 may irradiate light in the thickness direction of the first ring 112a and measure the thickness of the first ring 112a based on the interference light between a first reflected light reflected from the front surface of the first ring 112a and a second reflected light reflected from the back surface of the first ring 112a. The wear amount of the first ring 112a can be calculated from the measurement results. In this case, the control unit 2 may measure the wear amount of the first ring 112a every time a predetermined number of substrates W are processed. Note that the method for measuring the thickness of the first ring 112a is not limited to the above method, and any known method can be used.

[0053] Instead of directly measuring the wear amount of the first ring 112a, first correlation information between a previously measured wear amount or thickness of the first ring 112a and the supply time of source RF power indicating the time for which the first ring 112a has been exposed to plasma may be obtained by measurement in advance and stored in the storage unit 2a2. In this case, in step S1, the control unit 2 may refer to the first correlation information stored in the storage unit 2a2 and calculate the wear amount of the first ring 112a based on the total supply time of source RF power since the first ring 112a was newly installed or replaced. However, the method for measuring the wear amount of the first ring 112a is not limited to these.

[0054] Next, in step S2, the control unit 2 lowers the first ring 112 a based on the amount of wear of the first ring 112 a. In this step, the control unit 2 controls the lowering position of the first ring 112 a based on the amount of wear of the first ring 112 a so that the angle of incidence of ions in the plasma that are incident on the edge region of the substrate W becomes approximately perpendicular.

[0055] For example, the control unit 2 may acquire second correlation information in advance by measurement, the second correlation information being the amount of wear of the first ring 112a, the height of the first ring 112a from the bottom surface 112b1 of the recess of the second ring 112b that the first ring 112a faces, and the incident angle of the ions, and store the second correlation information in the storage unit 2a2. Then, in step S2, the control unit 2 may refer to the storage unit 2a2 and control the lowering position of the first ring 112a based on the amount of wear of the first ring 112a so that the incident angle of the ions becomes approximately vertical based on the second correlation information.

[0056] In step S2, the controller 2 lowers the first ring 112a as the wear amount of the first ring 112a increases. Based on the wear amount of the first ring 112a, the controller 2 gradually lowers the first ring 112a to control the inclination of the ion incident angle from an inward state to a more outward state, in response to the inclination of the ion incident angle becoming more inward. This allows the ion incident angle to be controlled to be approximately vertical by controlling the lowering position of the first ring 112a. As a result, the edge ring replacement cycle can be extended.

[0057] When bias RF power of 400 kHz is supplied, the impedance due to the gap D is larger than when bias RF power of, for example, 13 MHz is supplied. Therefore, when the first ring 112a is lowered relative to the potential of the first ring 112a in the initial state in Fig. 5A , the amount of change in the potential of the first ring 112a is large, and the gap D narrows, reducing the impedance. As a result, the potential of the first ring 112a rises above the potential in the initial position in Fig. 5A .

[0058] The thickness of the sheath is determined by the potential difference between the plasma and the edge ring. The larger the potential difference between the plasma and the edge ring, the thicker the sheath. Therefore, when the plasma is considered as ground, the lower the first ring 112a from FIG. 5A to FIG. 5B, the larger the potential difference between the plasma and the first ring 112a, resulting in a thicker sheath. That is, as a result of lowering the first ring 112a, the increase in the thickness of the sheath directly above the first ring 112a is greater than the amount of lowering of the top surface of the first ring 112a, and therefore the height position of the sheath directly above the first ring 112a becomes higher. As a result, when 400 kHz bias RF power is supplied, the lower the first ring 112a, the more outwardly (outer direction) the ions can be directed.

[0059] As the first ring 112a is consumed, the sheath S directly above it descends. As the sheath S descends, the ion incidence angle tilts inward. At this time, the first ring 112a is lowered by a height corresponding to the amount of consumption of the first ring 112a. This raises the sheath S, controlling the ion incidence angle to be more outward. This makes it possible to control the ion incidence angle to be approximately vertical by the lowered position of the first ring 112a. With this control, the ion incidence angle can be controlled to be approximately vertical even when bias RF power with a frequency of 400 kHz is supplied.

[0060] In step S2, the control unit 2 lowers the first ring 112a while controlling the first ring 112a so that it does not come into contact with the second ring 112b. The lowering of the first ring 112a is terminated before the first ring 112a comes into contact with the bottom surface 112b1 of the recess of the second ring 112b. This prevents the first ring 112a from coming into contact with the second ring 112b, causing a sudden change in the potential of the first ring 112a and reducing the controllability (control accuracy) of the ion incident angle. However, if the first ring 112a is made of a dielectric material such as quartz, the first ring 112a may come into contact with the second ring 112b.

[0061] Next, in step S3, the control unit 2 determines whether the amount of wear of the first ring 112a has reached a preset limit value. If the control unit 2 determines that the amount of wear of the first ring 112a has not reached the limit value, the control unit 2 returns to step S1, executes steps S1 and S2, and lowers the first ring 112a based on the amount of wear of the first ring 112a.

[0062] If the controller 2 determines in step S3 that the wear of the first ring 112a has reached a limit value, the controller 2 proceeds to step S4, replaces the first ring 112a, and ends this process. The limit value is determined in advance by measurement. For example, the limit value may be determined by measurement as the minimum thickness of the first ring 112a at which the ion incident angle can be controlled to be approximately perpendicular when the first ring 112a is lowered.

[0063] [Example of Experimental Results] Using the plasma processing apparatus 1, the controllability of the ion incident angle was compared between control for raising and control for lowering the first ring 112a when source RF power was supplied to the antenna 14 and bias RF power was supplied to the substrate support 11 (base 1110). When controlling to raise the first ring 112a, bias RF power with a frequency of 13 MHz was supplied to the base 1110. When controlling to lower the first ring 112a, bias RF power with a frequency of 400 kHz was supplied to the base 1110.

[0064] In addition, in the control of raising the first ring, experiments were conducted by changing the thickness E of the first ring 112a', which was the same as the operation of raising and lowering the first ring. As shown in FIG. 6A, when the thickness E of the first ring 112a' was set to 2.2 mm, the drive amount F of the first ring 112a' was defined as 0 (i.e., the first ring 112a' was not raised). When the thickness E of the first ring 112a' was set to 2.7 mm and 3.2 mm, the drive amount F of the first ring 112a' was defined as +0.5 and +1.0, respectively. When the thickness E of the first ring 112a' was set to 1.7 mm, the drive amount F of the first ring 112a' was defined as -0.5. The thickness E of the first ring 112a' was changed to 1.7 mm, 2.2 mm, 2.7 mm, and 3.2 mm, thereby controlling the height of the first ring 112a' to be raised or lowered by the thickness of the first ring 112a'.

[0065] In the control for lowering the first ring, as shown in FIG. 6B, two thicknesses E of the first ring 112a, 3.2 mm and 2.7 mm, were prepared, and the first ring 112a of each thickness was actually raised and lowered using the support pin 51, and the drive amount F was changed in increments of 0.5 mm.

[0066] 6C and 6D, the ion incident angle (tilt) is indicated by a positive sign when it is tilted outward, and by a negative sign when it is tilted inward. The horizontal axis of FIG. 6D represents the drive amount of the first rings 112a′ and 112a, and the vertical axis represents the ion incident angle.

[0067] When the drive amount F was 0 mm (thickness 2.2 mm), the ion incident angle was tilted outward (outer direction) by 1.86 degrees for the 3.2 mm thick first ring 112a. When the drive amount F was 1 mm (thickness 3.2 mm), the ion incident angle was tilted inward (inner direction) by -0.91 degrees for the 3.2 mm thick first ring 112a. From this result, it was found that when the 3.2 mm thick first ring 112a was raised, the ion incident angle was controlled from the outer direction to the inner direction.

[0068] Similarly, it was found that when the first ring 112a with a thickness of 2.7 mm was raised, the ion incident angle was controlled from the outer direction to the inner direction. In other words, when the first ring 112a with a thickness of 3.2 mm or 2.7 mm was lowered, the ion incident angle was controlled from the inner direction to the outer direction.

[0069] Next, for the first ring 112a having a thickness of 3.2 mm, the tilting (ion incident angle) sensitivity was 2.77 degrees (deg / mm) when the driving amount F was changed from 0 mm to 1 mm, and the ion incident angle changed in the inner direction.

[0070] On the other hand, for the first ring 112a with a thickness of 2.7 mm, the tilting (ion incident angle) sensitivity was 2.19 degrees (deg / mm) when the drive amount F was changed from 0 mm to 1 mm, and the ion incident angle changed in the inward direction. In other words, for the first ring 112a with thicknesses of 3.2 mm and 2.7 mm, when the first ring 112a was lowered by the same drive amount, the thicker the first ring 112a, the higher the tilting (ion incident angle) sensitivity.

[0071] The distance from the first ring 112a to the plasma depends on the drive amount of the first ring 112a and the thickness of the first ring 112a. The thicker the first ring 112a, the more the sheath S is pushed up. As a result, it is thought that the thicker the first ring 112a, the larger the controlled angle and the higher the sensitivity, i.e., the better the controllability of the ion incident angle.

[0072] 6A, when the thickness of the first ring 112a' was increased, and the drive amount F was changed from 0 mm to 1 mm (in practice, the thickness of the first ring 112a' was increased from 2.2 mm to 3.2 mm), the ion incident angle shifted 1.69 degrees outward. Furthermore, when the thickness of the first ring 112a' was increased from 1.7 mm to 3.2 mm, the sensitivity of the ion incident angle was 1.402 (deg / mm). These experimental results demonstrate that the sensitivity of the ion incident angle is higher when the first ring 112a is lowered than when it is raised.

[0073] 6D, when the first ring 112a is lowered, lines B and C, which show the ion incident angle (tilt) when the first ring 112a with a thickness of 3.2 mm and 2.7 mm is lowered, indicate that the ion incident angle can be controlled from the inner direction to the outer direction. When "lowering the first ring 112a," the drive amount of the first ring 112a on the horizontal axis of FIG. 6D changes from a positive value to a zero value.

[0074] In contrast, when the first ring 112a' is raised, the ion incident angle (Tilt) can be controlled from the inner direction to the outer direction as shown by line A, which indicates the ion incident angle (Tilt) when the first ring 112a' is raised. Note that when "raising the first ring 112a'", the drive amount of the first ring 112a' on the horizontal axis of FIG. 6D is changed from a drive amount of 0 to a positive value.

[0075] [Example of Effect] In the edge ring control method according to this embodiment, the initial position of the first ring 112 a is raised to a preset height, and the first ring 112 a is lowered according to the amount of wear of the first ring 112 a. As a result, in a low-frequency process using bias RF power with a frequency of less than 13 MHz, it is possible to control the angle of incidence of ions incident on the edge region with greater sensitivity using the same parts configuration as in a high-frequency process using bias RF power with a frequency of 13 MHz or higher.

[0076] Furthermore, the structure can be simplified and the number of parts can be reduced when controlling the ion incident angle in a low-frequency process. Furthermore, by preliminarily adjusting the thickness of the volatilizable ring of the edge ring to be thick, the ion incident angle can be controlled to be perpendicular, thereby obtaining a perpendicular etching profile in the edge region of the substrate W. In addition, the volatilizable ring can withstand wear during plasma etching for a long period of time, thereby extending the replacement cycle of the volatilizable ring. In this case, the thickness of the volatilizable ring may be set higher than the height of the upper surface of the substrate W, and the ion incident angle may be slightly tilted toward the outer side when the lifter 50 is driven at 0 mm.

[0077] The embodiments disclosed above include, for example, the following aspects. (Supplementary Note 1) A plasma processing apparatus comprising: a substrate support disposed in a plasma processing chamber and supporting a substrate; an edge ring disposed around the substrate supported on the substrate support; a lifter configured to raise and lower the edge ring; and a controller, wherein the controller controls the steps of: preparing a substrate on the substrate support and processing the substrate with plasma; measuring a wear rate of the edge ring; and controlling the lifter to lower the edge ring based on the wear rate of the edge ring. (Supplementary Note 2) The plasma processing apparatus according to Supplementary Note 1, further comprising: a bias RF power supply configured to supply bias RF power having a frequency less than 13 MHz to the substrate support. (Supplementary Note 3) The plasma processing apparatus according to Supplementary Note 1 or 2, further comprising: a source RF power supply configured to supply source RF power having a frequency of 13 MHz or greater to an antenna, an upper electrode, or the substrate support disposed at or above the plasma processing chamber. (Supplementary Note 4) The plasma processing apparatus according to any one of Supplementary Notes 1 to 3, wherein the control unit controls to lower the edge ring based on a wear amount of the edge ring so that an incident angle of ions incident on the edge region of the substrate becomes approximately perpendicular. (Supplementary Note 5) The plasma processing apparatus according to any one of Supplementary Notes 1 to 4, wherein the control unit controls to start lowering the edge ring from an initial position of the edge ring where the edge ring is raised to a preset height. (Supplementary Note 6) The plasma processing apparatus according to Supplementary Note 5, wherein the initial position of the edge ring is a height of the uppermost portion of the edge ring at which an incident angle of ions incident on the edge region of the substrate becomes approximately perpendicular when the edge ring is not worn. (Supplementary Note 7) The plasma processing apparatus according to any one of Supplementary Notes 1 to 6, wherein the control unit controls a process of acquiring correlation information between the amount of wear of the edge ring, the height to which the edge ring is raised, and the angle of incidence of ions incident on the edge region of the substrate by prior measurement and storing the information in a memory unit, and controls the edge ring to be lowered based on the amount of wear of the edge ring by referring to the memory unit so that the angle of incidence of the ions becomes approximately vertical based on the correlation information.(Supplementary Note 8) The plasma processing apparatus according to any one of Supplementary Notes 1 to 7, wherein the edge ring includes a first ring that surrounds the periphery of the substrate and is movable up and down, and a second ring that supports the first ring, and the control unit controls to lower the first ring based on the amount of wear of the first ring. (Supplementary Note 9) The plasma processing apparatus according to Supplementary Note 8, wherein the control unit controls a step of determining whether the amount of wear of the first ring has reached a preset limit value, lowers the first ring based on the amount of wear of the first ring if it is determined that the amount of wear of the first ring has not reached the limit value, and controls to replace the first ring if it is determined that the amount of wear of the first ring has reached the limit value. (Supplementary Note 10) The plasma processing apparatus according to Supplementary Note 8 or 9, wherein the control unit controls to lower the first ring while preventing the first ring from contacting the second ring. (Supplementary Note 11) The plasma processing apparatus according to any one of Supplementary Notes 8 to 10, wherein the control unit controls the lowering of the edge ring to finish before the first ring contacts a bottom surface of a recessed portion of the second ring facing the first ring. (Supplementary Note 12) The plasma processing apparatus according to Supplementary Note 2, wherein the substrate support unit includes a base and an electrostatic chuck arranged on the base and having a substrate support surface for supporting the substrate and a ring support surface on which the edge ring is placed, and the bias RF power is supplied to the base. (Supplementary Note 13) A method for controlling an edge ring executed in a plasma processing apparatus including: a substrate support unit arranged in a plasma processing chamber and supporting a substrate; an edge ring arranged around the substrate supported by the substrate support unit; and a lifter for raising and lowering the edge ring, the method comprising: a step of measuring a wear rate of the edge ring; and a step of lowering the edge ring by the lifter based on the wear rate of the edge ring.

[0078] The present invention is not limited to the configurations described in the above embodiments, and may be combined with other elements. These aspects can be modified without departing from the spirit of the present invention and can be appropriately determined depending on the application form. Furthermore, the matters described in the multiple embodiments can be configured in other ways as long as they are not inconsistent, and can be combined as long as they are not inconsistent.

[0079] For example, although the above embodiment has been described using an inductively coupled plasma device as an example, the present invention is not limited thereto and may be applied to other plasma devices. For example, a capacitively coupled plasma (CCP) device may be used instead of the inductively coupled plasma device. In this case, the capacitively coupled plasma device includes opposing upper and lower electrodes. The lower electrode is disposed within the substrate support, and the upper electrode is disposed above the processing chamber. Therefore, the RF generator is coupled to the upper electrode of the capacitively coupled plasma device or the antenna of the inductively coupled plasma device. That is, the RF generator is coupled to the plasma processing chamber 10.

[0080] This application claims priority based on Japanese Patent Application No. 2023-212650, filed on December 18, 2023, the entire contents of which are incorporated herein by reference.

[0081] REFERENCE SIGNS LIST 1 Plasma processing apparatus 2 Control unit 2a Computer 2a1 Processing unit 2a2 Memory unit 2a3 Communication interface 10 Plasma processing chamber 11 Substrate support 13 Central gas injection unit 21 Gas source 20 Gas supply unit 30 Power supply 31 RF power supply 40 Exhaust system 50 Lifter 51 Support pin 52 Actuator 111 Main body 112 Ring assembly 112a First ring 112b Second ring

Claims

1. A plasma processing apparatus comprising: a substrate support part disposed within a plasma processing chamber for supporting a substrate; an edge ring disposed around the substrate supported on the substrate support part; a lifter for raising and lowering the edge ring; and a control part, wherein the control part controls the steps of: preparing a substrate on the substrate support part and processing the substrate with plasma; measuring the amount of wear of the edge ring; and controlling the lifter to lower the edge ring based on the amount of wear of the edge ring.

2. The plasma processing apparatus according to claim 1, further comprising a bias RF power supply for supplying a bias RF power having a frequency of less than 13 MHz to the substrate support.

3. The plasma processing apparatus according to claim 2, further comprising a source RF power supply for supplying a source RF power having a frequency of 13 MHz or more to an antenna, an upper electrode, or the substrate support disposed at or above the plasma processing chamber.

4. A plasma processing apparatus according to any one of claims 1 to 3, wherein the control unit controls the edge ring to be lowered based on the amount of wear of the edge ring so that the angle of incidence of ions incident on the edge region of the substrate becomes approximately perpendicular.

5. The plasma processing apparatus according to any one of claims 1 to 3, wherein the control unit controls the edge ring to start lowering from an initial position where the edge ring is raised to a preset height.

6. The plasma processing apparatus according to claim 5, wherein the initial position of the edge ring is the height of the uppermost portion of the edge ring at which an incident angle of ions incident on the edge region of the substrate becomes approximately perpendicular when the edge ring is not worn.

7. A plasma processing apparatus as described in any one of claims 1 to 3, wherein the control unit controls a process of obtaining correlation information between the amount of wear of the edge ring, the height to which the edge ring is raised, and the angle of incidence of ions incident on the edge region of the substrate by prior measurement and storing the information in a memory unit, and by referring to the memory unit, controls the edge ring to be lowered based on the amount of wear of the edge ring so that the angle of incidence of the ions becomes approximately vertical based on the correlation information.

8. A plasma processing apparatus as described in any one of claims 1 to 3, wherein the edge ring comprises a first ring that surrounds the periphery of the substrate and is capable of being raised and lowered, and a second ring that supports the first ring, and the control unit controls the first ring to be lowered based on the amount of wear of the first ring.

9. The plasma processing apparatus of claim 8, wherein the control unit controls a process of determining whether the amount of wear of the first ring has reached a preset limit value; if it is determined that the amount of wear of the first ring has not reached the limit value, the control unit lowers the first ring based on the amount of wear of the first ring; and if it is determined that the amount of wear of the first ring has reached the limit value, the control unit controls to replace the first ring.

10. The plasma processing apparatus according to claim 8, wherein the control unit controls the first ring to be lowered while preventing the first ring from contacting the second ring.

11. The plasma processing apparatus according to claim 8, wherein the control unit controls the edge ring to finish lowering before the first ring comes into contact with a bottom surface of a recess in the second ring facing the first ring.

12. The plasma processing apparatus according to claim 2, wherein the substrate support comprises a base, and an electrostatic chuck arranged on the base and having a substrate support surface for supporting the substrate and a ring support surface for placing the edge ring, and the bias RF power is supplied to the base.

13. A method for controlling an edge ring in a plasma processing apparatus including a substrate support disposed within a plasma processing chamber for supporting a substrate, an edge ring disposed around the substrate supported on the substrate support, and a lifter for raising and lowering the edge ring, the method comprising the steps of: measuring an amount of wear of the edge ring; and lowering the edge ring by the lifter based on the amount of wear of the edge ring.

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