Cleaning method for plasma processing device and plasma processing device

Abstract

A cleaning method for a plasma processing device according to the present invention includes (a) a step for introducing a cleaning gas into a chamber of the plasma processing device, (b) a step for generating plasma in the chamber under a first condition to perform a first cleaning, and (c) a step for generating plasma in the chamber under a second condition to perform a second cleaning. At least one of the first condition and the second condition is adjusted such that a first ratio between the thickness of the inner sheath and the thickness of the outer sheath of the plasma generated at step (b) is different from a second ratio between the thickness of the inner sheath and the thickness of the outer sheath of the plasma generated at step (c).

Description

Cleaning method for plasma processing apparatus and plasma processing apparatus

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

[0002] Patent Document 1 discloses a plasma processing apparatus including an upper electrode, which includes a first upper electrode and a second upper electrode that is disposed around the first upper electrode and insulated from the first upper electrode.

[0003] JP 2017-112275 A

[0004] The technology according to the present disclosure efficiently cleans a plasma processing apparatus.

[0005] One aspect of the present disclosure is a cleaning method for a plasma processing apparatus, comprising: (a) a step of introducing a cleaning gas into a chamber of the plasma processing apparatus; (b) a step of generating plasma in the chamber under first conditions to perform a first cleaning; and (c) a step of generating plasma in the chamber under second conditions to perform a second cleaning, wherein at least one of the first conditions and the second conditions is adjusted so that a first ratio of the thickness of the inner sheath to the thickness of the outer sheath in the sheath of the plasma generated in the (b) step is different from a second ratio of the thickness of the inner sheath to the thickness of the outer sheath in the sheath of the plasma generated in the (c) step.

[0006] According to the present disclosure, cleaning of a plasma processing apparatus can be performed efficiently.

[0007] FIG. 1 is an explanatory diagram schematically showing the configuration of a plasma processing system. FIG. 1 is an explanatory diagram showing a state in which a gap between an inner upper electrode and an outer upper electrode is cleaned. FIG. 2 is an explanatory diagram showing a state in which a gap between an inner upper electrode and an outer upper electrode is cleaned. FIG. 3 is an explanatory diagram showing a state in which a gap between an inner upper electrode and an outer upper electrode is cleaned. FIG. 4 is an explanatory diagram showing an example of a method for cleaning a gap between an inner upper electrode and an outer upper electrode. FIG. 5 is an explanatory diagram showing behavior of deposits removed from the gap. FIG. 1 is an explanatory diagram showing an example of a method for cleaning a gap between an inner upper electrode and an outer upper electrode in another embodiment. FIG. 2 is an explanatory diagram showing a state in which a gap between an inner upper electrode and an outer upper electrode is cleaned in another embodiment. FIG. 3 is an explanatory diagram showing a state in which a gap between an inner upper electrode and an outer upper electrode is cleaned in another embodiment. FIG. 4 is an explanatory diagram showing a state in which a gap between an electrostatic chuck and an edge ring is cleaned.

[0008] In the manufacturing process of semiconductor devices, various plasma processes such as etching, film formation, and diffusion are performed on semiconductor substrates (hereinafter referred to as "substrates") In plasma processes, plasma is generated by exciting a process gas, and the substrate is processed by the plasma.

[0009] The plasma processing is performed using, for example, a capacitively coupled plasma (CCP) plasma processing apparatus. The plasma processing apparatus includes a chamber, a substrate support, a plasma generation unit, and the like. The plasma processing apparatus also includes an upper electrode that forms at least a part of the chamber ceiling, and a lower electrode provided on the substrate support. For example, as disclosed in Patent Document 1, the upper electrode includes a first upper electrode (inner upper electrode) and a second upper electrode (outer upper electrode). The outer upper electrode is provided to surround the inner upper electrode, and the inner upper electrode and the outer upper electrode are insulated from each other.

[0010] In plasma processing, reaction products are generated. These reaction products adhere to the sidewalls of the chamber and components inside the chamber, and accumulate as deposits. In particular, if deposits accumulate in the minute gap formed between the inner upper electrode and the outer upper electrode, the gap narrows, which can cause abnormal discharge. Therefore, to remove the deposits, dry cleaning using plasma is performed inside the chamber. That is, in dry cleaning, a cleaning gas is excited to generate plasma, and the deposits are removed using this plasma. Specifically, dry cleaning removes deposits through chemical reactions caused by radicals and physical reactions caused by ions (sputtering).

[0011] However, in conventional dry cleaning, for example, a constant DC voltage is applied to the inner upper electrode and the outer upper electrode, and ions are incident in one direction into the minute gap between the inner upper electrode and the outer upper electrode, making it difficult to remove deposits that have adhered to the gap. Furthermore, the deposits are, for example, compounds containing yttrium (Y), and such deposits are difficult to remove chemically. Therefore, there is room for improvement in conventional cleaning methods.

[0012] The technology disclosed herein efficiently cleans a plasma processing apparatus. Hereinafter, a plasma processing apparatus and a dry cleaning method for a plasma processing apparatus according to this embodiment will be described with reference to the drawings. Note that in this specification and the drawings, elements having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0013] <Plasma Processing System and Plasma Processing Apparatus> 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 a capacitively coupled plasma processing apparatus.

[0014] The plasma processing system includes a capacitively coupled plasma processing apparatus 1 and a controller 2. The capacitively coupled plasma processing apparatus 1 includes a plasma processing chamber 10, a gas supply unit 20, a power supply 30, and an exhaust system 40. The plasma processing apparatus 1 also includes a substrate support 11 and a gas inlet. The gas inlet is configured to introduce at least one process gas or at least one cleaning gas into the plasma processing chamber 10. The gas inlet includes a showerhead assembly 13. The substrate support 11 is disposed within the plasma processing chamber 10. The showerhead assembly 13 is disposed above the substrate support 11. In one embodiment, the showerhead assembly 13 forms at least a portion of the ceiling of the plasma processing chamber 10. The showerhead assembly 13 is supported on a sidewall 10a of the plasma processing chamber 10 via an insulating member (not shown). The plasma processing chamber 10 has a plasma processing space 10s defined by the showerhead assembly 13, the sidewall 10a of the plasma processing chamber 10, and the substrate support 11. The plasma processing chamber 10 has at least one gas inlet for supplying at least one processing gas or at least one cleaning gas into the plasma processing space 10s and at least one gas outlet for exhausting gas from the plasma processing space 10s. The plasma processing chamber 10 is grounded. The showerhead assembly 13 and the substrate support 11 are electrically insulated from the housing of the plasma processing chamber 10.

[0015] The substrate support 11 includes a main body 111 and a ring assembly 112. The main body 111 has a central region 111a for supporting a substrate W and an annular region 111b for supporting the 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, and 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.

[0016] 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 lower 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 lower electrode. When a bias RF signal and / or a DC signal (described later) is supplied to the at least one RF / DC electrode, the RF / DC electrode is also called a bias electrode. Note that the conductive member of the base 1110 and the at least one RF / DC electrode may function as multiple lower electrodes. Furthermore, the electrostatic electrode 1111b may function as a lower electrode. Therefore, the substrate support 11 includes at least one lower electrode.

[0017] 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 113 and at least one cover ring 114. The edge ring 113 is annularly provided to surround the substrate W on the main body 111. The cover ring 114 is annularly provided to surround the edge ring 113. The edge ring 113 is formed of a conductive material or an insulating material, and in the case of a conductive material, for example, it is formed of Si or SiC. The cover ring 114 is formed of an insulating material.

[0018] 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 W 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 back surface of the substrate W and the central region 111a.

[0019] The showerhead assembly 13 is configured to introduce at least one processing gas or at least one cleaning gas from the gas supply unit 20 into the plasma processing space 10s. The showerhead assembly 13 has at least one gas supply port 13a, at least one gas diffusion chamber 13b, and multiple gas inlets 13c. The processing gas or cleaning gas supplied to the gas supply port 13a passes through the gas diffusion chamber 13b and is introduced into the plasma processing space 10s from the multiple gas inlets 13c. In addition to the showerhead assembly 13, the gas inlet may include one or more side gas injectors (SGIs) attached to one or more openings formed in the sidewall 10a.

[0020] The showerhead assembly 13 includes at least one upper electrode. In one embodiment, the showerhead assembly 13 includes an inner upper electrode 130, an outer upper electrode 131, and an electrode support 132. The inner upper electrode 130 is provided above the central region 111a of the main body 111. The inner upper electrode 130 is an electrode plate having a substantially circular plate shape. The outer upper electrode 131 is provided above the annular region 111b (ring assembly 112) of the main body 111 so as to surround the inner upper electrode 130. The outer upper electrode 131 is an electrode plate having a substantially annular shape. The inner upper electrode 130 and the outer upper electrode 131 are each formed of a conductive material, such as Si or SiC. The electrode support 132 detachably supports the inner upper electrode 130 and the outer upper electrode 131. The electrode support 132 is formed of a conductive material, such as aluminum.

[0021] The gas supply 20 may include at least one gas source 21 and at least one flow controller 22. In one embodiment, the gas supply 20 is configured to supply at least one process gas or at least one cleaning gas from a corresponding gas source 21 through a corresponding flow controller 22 to the showerhead assembly 13. Each flow controller 22 may include, for example, a mass flow controller or a pressure-controlled flow controller. Additionally, the gas supply 20 may include one or more flow modulation devices to modulate or pulse the flow rate of the at least one process gas or the at least one cleaning gas.

[0022] 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 lower electrode and / or at least one upper electrode 130, 131. This generates a plasma from at least one processing gas or at least one cleaning 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 processing gases or one or more cleaning gases in the plasma processing chamber 10. Furthermore, by supplying a bias RF signal to the at least one lower electrode, a bias potential is generated on the substrate W, thereby attracting ion components in the formed plasma to the substrate W.

[0023] 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 is coupled to at least one lower electrode and / or at least one upper electrode 130, 131 via at least one impedance matching circuit and is configured to generate a source RF signal (source RF power) for plasma generation. In one embodiment, the source RF signal has a frequency in the range of 10 MHz to 150 MHz. 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 at least one lower electrode and / or at least one upper electrode 130, 131.

[0024] The second RF generator 31b is coupled to at least one lower electrode via at least one impedance matching circuit and is 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 60 MHz. In one embodiment, the second RF generator 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 lower electrode. In various embodiments, at least one of the source RF signal and the bias RF signal may be pulsed.

[0025] 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 first DC generator 32a, a second DC generator 32b, a third DC generator 32c, and a fourth DC generator 32d. In one embodiment, the first DC generator 32a is connected to the inner upper electrode 130 and configured to generate a first DC signal. The generated first bias DC signal is applied to the inner upper electrode 130. In one embodiment, the second DC generator 32b is connected to the outer upper electrode 131 and configured to generate a second DC signal. The generated second bias DC signal is applied to the outer upper electrode 131. In one embodiment, the third DC generator 32c is connected to at least one lower electrode and configured to generate a third DC signal. The generated third bias DC signal is applied to at least one lower electrode. In one embodiment, the fourth DC generator 32d is connected to one or more edge rings 113 and configured to generate a fourth DC signal. The generated fourth DC signal is applied to the one or more edge rings 113.

[0026] In various embodiments, at least one of the first to third DC signals may be pulsed. In this case, a sequence of voltage pulses is applied to at least one upper electrode 130, 131 and / or at least one lower electrode. The voltage pulses may have a rectangular, trapezoidal, triangular, or combination thereof. In one embodiment, a waveform generator for generating a sequence of voltage pulses from the DC signal is connected between the first DC generator 32a and the inner upper electrode 130. Thus, the first DC generator 32a and the waveform generator constitute a voltage pulse generator. When the second DC generator 32b and the waveform generator constitute a voltage pulse generator, the voltage pulse generator is connected to the outer upper electrode 131. When the third DC generator 32c and the waveform generator constitute a voltage pulse generator, the voltage pulse generator is connected to at least one lower electrode. The voltage pulses may have positive or negative polarity. The voltage pulse sequence may include one or more positive voltage pulses and one or more negative voltage pulses within one cycle. The first to third DC generators 32a to 32c may be provided in addition to the RF power supply 31, or the third DC generator 32c may be provided instead of the second RF generator 31b.

[0027] 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.

[0028] 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).

[0029] <Plasma Processing Method> Next, a plasma processing performed using the plasma processing apparatus 1 configured as above will be described.

[0030] First, the substrate W is carried into the plasma processing chamber 10 and placed on the electrostatic chuck 1111 of the substrate support part 11. Next, a voltage is applied to the electrostatic electrode 1111b of the electrostatic chuck 1111, so that the substrate W is attracted and held on the electrostatic chuck 1111 by electrostatic force.

[0031] After the substrate W is attracted and held by the electrostatic chuck 1111, the inside of the plasma processing chamber 10 is subsequently depressurized to a predetermined vacuum level. Next, a processing gas is supplied from the gas supply unit 20 to the plasma processing space 10s via the shower head assembly 13. Furthermore, source RF power for plasma generation is supplied from the first RF generator 31a to the lower electrode, thereby exciting the processing gas to generate plasma. At this time, bias RF power may be supplied from the second RF generator 31b. Then, in the plasma processing space 10s, the substrate W is subjected to plasma processing by the action of the generated plasma.

[0032] <Cleaning Method> In plasma processing, reaction products are generated. The reaction products adhere to the sidewall 10a of the plasma processing chamber 10 and components inside the plasma processing chamber 10, and accumulate as deposits. Therefore, in order to remove the deposits, dry cleaning using plasma is performed inside the plasma processing chamber 10. That is, in dry cleaning, a cleaning gas is excited to generate plasma, and the deposits are removed using the plasma. The type of cleaning gas is appropriately selected depending on the type of deposit. For example, when the deposits are yttrium compounds, the cleaning gas contains O. ２ A gas is used.

[0033] Dry cleaning can be performed with or without a dummy substrate supported by the substrate support 11 (substrate-less dry cleaning). In either dry cleaning method, the plasma processing chamber 10 is first depressurized to a predetermined vacuum level, as in plasma processing. Next, a cleaning gas is supplied from the gas supply unit 20 to the plasma processing space 10s via the showerhead assembly 13. Furthermore, source RF power for plasma generation is supplied from the first RF generator 31a to the lower electrode, thereby exciting the cleaning gas to generate plasma. At this time, bias RF power may be supplied from the second RF generator 31b. The plasma generated in the plasma processing space 10s then cleans the inside of the plasma processing chamber 10.

[0034] [Cleaning of the Upper Electrode] If reaction products adhere to and deposit material in the minute gap G formed between the inner upper electrode 130 and the outer upper electrode 131, the gap G may narrow, potentially causing abnormal discharge. However, in conventional dry cleaning, a constant DC voltage is applied to the upper electrode, and ions are incident on the gap G in one direction, making it difficult to remove the material that has deposited in the gap G. Therefore, in this embodiment, the thickness of the plasma sheath below the inner upper electrode 130 and the thickness of the plasma sheath below the outer upper electrode 131 are controlled, respectively, and the direction of ion incidence on the gap G is controlled, thereby removing the material that has deposited in the gap G.

[0035] Here, the thickness of the plasma sheath can be calculated, for example, by the following formula (1). However, V ｄｃ is the self-bias voltage (self-bias potential), Te is the plasma temperature, Ne is the plasma density, ε ０ is the dielectric constant of a vacuum, and e is the elementary charge.

[0036] According to the above formula (1), a larger self-bias voltage results in a larger sheath thickness, and a smaller self-bias voltage results in a smaller sheath thickness. Therefore, in this embodiment, the DC voltage (hereinafter referred to as the "inner DC voltage") applied from the first DC generator 32a to the inner upper electrode 130 is controlled to control the self-bias voltage of the inner upper electrode 130. In addition, the DC voltage (hereinafter referred to as the "outer DC voltage") applied from the second DC generator 32b to the outer upper electrode 131 is controlled to control the self-bias voltage of the outer upper electrode 131.

[0037] 2 to 4 are explanatory diagrams showing how the gap G between the inner upper electrode 130 and the outer upper electrode 131 is cleaned. In the following description, the sheath of plasma generated below the inner upper electrode 130 is referred to as the inner sheath Sa, and the sheath of plasma generated below the outer upper electrode 131 is referred to as the outer sheath Sb. The thickness da of the inner sheath Sa is the distance from the plasma to the lower surface of the inner upper electrode 130, and the thickness db of the outer sheath Sb is the distance from the plasma to the lower surface of the outer upper electrode 131.

[0038] FIG. 2 is an explanatory diagram illustrating a case where the inner DC voltage is greater than the outer DC voltage. In the following description, this cleaning condition is referred to as the first condition. In this case, the thickness da of the inner sheath Sa is greater than the thickness db of the outer sheath Sb. As a result, the incident direction of ions into the gap G (indicated by the arrow in the figure) is tilted from the vertical toward the inner upper electrode 130, and ions are incident on the side surface Ga of the gap G on the inner upper electrode 130 side. This side surface Ga then becomes the cleaning target area (the shaded area in the figure), and deposits D attached to the side surface Ga are removed by the ions. The removed deposits D are discharged from a gas exhaust port 10e provided at the bottom of the plasma processing chamber 10.

[0039] Furthermore, by controlling the ratio da / db (hereinafter referred to as "thickness ratio") of the thickness da of the inner sheath Sa to the thickness db of the outer sheath Sb, it is possible to adjust the tilt angle of the ion incident direction from the vertical direction. That is, the larger the thickness ratio da / db, the larger the tilt angle of the ions. Note that instead of the thickness ratio da / db, the difference between the thickness da of the inner sheath Sa and the thickness db of the outer sheath Sb may be controlled.

[0040] 3 is an explanatory diagram illustrating a case where the inner DC voltage and the outer DC voltage are the same. In the following description, this cleaning condition is referred to as the second condition. In this case, the thickness da of the inner sheath Sa and the thickness db of the outer sheath Sb are the same. In this case, the incident direction of ions into the gap G (indicated by the arrow in the figure) becomes vertical, and ions are incident on the upper surface Gb of the gap G. This upper surface Gb then becomes the area to be cleaned (the shaded area in the figure), and deposits D attached to the upper surface Gb are removed by the ions and discharged from the gas exhaust port 10e.

[0041] FIG. 4 is an explanatory diagram illustrating a case where the inner DC voltage is smaller than the outer DC voltage. In the following description, this cleaning condition is referred to as the third condition. In this case, the thickness da of the inner sheath Sa is smaller than the thickness db of the outer sheath Sb. As a result, the incident direction of ions into the gap G (indicated by the arrow in the figure) is tilted from the vertical toward the outer upper electrode 131, and ions are incident on the side surface Gc of the gap G on the outer upper electrode 131 side. This side surface Gc then becomes the cleaning target area (the shaded area in the figure), and deposits D attached to the side surface Gc are removed by the ions and discharged from the gas exhaust port 10e. Furthermore, in this case, when the sheath thickness ratio da / db is small, the tilt angle of the ions becomes large.

[0042] In this embodiment, after introducing a cleaning gas into the plasma processing space 10s, the first cleaning under the first condition ( FIG. 2 ), the second cleaning under the second condition ( FIG. 3 ), and the third cleaning under the third condition ( FIG. 4 ) are sequentially performed. Note that, as described above, these first to third conditions involve varying the inner DC voltage and the outer DC voltage, but other conditions, such as the source RF power and bias RF power supplied to the lower electrode, remain the same. In this case, the side surface Ga, the upper surface Gb, and the side surface Gc of the gap G can be sequentially cleaned, thereby efficiently cleaning a wide area of ​​the gap G. Furthermore, as a result, abnormal discharge between the inner upper electrode 130 and the outer upper electrode 131 can be suppressed.

[0043] FIG. 5 is an explanatory diagram showing an example of a method for cleaning the gap G. In FIG. 5, the values ​​of the inner DC voltage and the outer DC voltage are merely examples and are not limited to these. The cleaning area indicates the area to be cleaned from which the deposits D are removed. The arrow of the incident ions indicates the direction of incidence of the ions into the gap G and the removal force of the deposits D by the ions (hereinafter referred to as "sputtering force"). The direction of incidence of the ions is indicated by the direction of the arrow, and as in FIGS. 2 to 4, the left side from the vertical direction is the inner upper electrode 130 side, and the right side is the outer upper electrode 131 side. The sputtering force of the ions is indicated by the thickness of the arrow.

[0044] Steps S1 and S2 are the first cleaning under the first condition ( FIG. 2 ). The inner DC voltage is greater than the outer DC voltage, and the ion incidence direction is tilted from the vertical toward the inner upper electrode 130, cleaning the side surface Ga. In steps S1 and S2, the inner DC voltage is fixed at 500 V, and the outer DC voltage is increased to 150 V and 300 V. That is, the outer DC voltage is gradually varied (swept) toward step S3, which will be described later. This gradually varies and decreases the sheath thickness ratio da / db, and the ion tilt angle gradually decreases. Furthermore, as the outer DC voltage increases, the ion sputtering force increases.

[0045] Step S3 is a second cleaning under the second condition (FIG. 3), in which the inner and outer DC voltages are the same at 500 V, the ion incidence direction is vertical, and the upper surface Gb is cleaned.

[0046] Steps S4 to S8 are the third cleaning under the third condition ( FIG. 4 ). The inner DC voltage is smaller than the outer DC voltage, and the ion incidence direction is tilted from the vertical toward the outer upper electrode 131, cleaning the side surface Gc. In steps S4 to S8, the inner DC voltage is fixed at 300 V, and the outer DC voltage is gradually increased from 500 V to 1400 V. This gradually decreases the sheath thickness ratio da / db, and gradually increases the tilt angle of the ions. Furthermore, as the outer DC voltage increases, the sputtering force of the ions increases.

[0047] According to this embodiment, by controlling the inner DC voltage and the outer DC voltage, more specifically by controlling the balance (ratio) between the inner DC voltage and the outer DC voltage, the sheath thickness ratio da / db can be controlled, and the incident direction of ions into the gap G can be arbitrarily controlled. Then, by sequentially performing the first to third cleanings, the side surface Ga, upper surface Gb, and side surface Gc in the gap G are sequentially cleaned, and the deposits D on the side surface Ga, upper surface Gb, and side surface Gc can be efficiently removed.

[0048] Furthermore, by controlling the magnitude of the inner DC voltage and the outer DC voltage, the sputtering power of the ions can be controlled, and therefore the deposits D on the side surface Ga, the upper surface Gb, and the side surface Gc can be removed more efficiently.

[0049] In the first cleaning (steps S1 to S2), the outer DC voltage is varied in stages, and the tilt angle of the ions is varied in stages, so that ions are caused to collide with the entire surface of the side surface Ga, thereby enabling a wide cleaning of the side surface Ga. Furthermore, in the third cleaning (steps S4 to S8), the outer DC voltage is also varied in stages, and the tilt angle of the ions is also varied in stages, so that ions are caused to collide with the entire surface of the side surface Gc, enabling a wide cleaning of the side surface Gc.

[0050] 6, for example, when cleaning the side surface Ga of the gap G, the deposits D removed from the side surface Ga may not be discharged from the gap G and may re-adhere to the upper surface Gb or the side surface Gc. Therefore, it is preferable to repeatedly perform a first cleaning under first conditions (FIG. 2), a second cleaning under second conditions (FIG. 3), and a third cleaning under third conditions (FIG. 4).

[0051] 7 is an explanatory diagram showing an example of a method for cleaning the gap G according to another embodiment. In this embodiment, steps S9 to S14 are performed following steps S1 to S8 of the above embodiment shown in FIG.

[0052] Steps S9 to S12 are cleaning under third conditions ( FIG. 4 ) that continue from step S8, and clean the side surface Gc. In steps S9 to S12, the inner DC voltage is fixed at 300 V, continuing from step S8, and the outer DC voltage is gradually decreased from step S8, specifically from 1200 V to 500 V. That is, in the third cleaning, the outer DC voltage is gradually increased in steps S4 to S8, and then gradually decreased in steps S8 to S12. As a result, in steps S9 to S12, the sheath thickness ratio da / db also gradually increases, and the ion tilt angle gradually decreases. Furthermore, as the outer DC voltage decreases, the sputtering power of the ions decreases.

[0053] Step S13 is a second cleaning under the second condition (FIG. 3), in which the upper surface Gb is cleaned. In step S13, the inner DC voltage is set to 500 V, which is higher than in step S12, and the outer DC voltage is maintained at 500 V from step S12. That is, in step S13, the inner DC voltage and the outer DC voltage are the same, 500 V.

[0054] Step S14 is the first cleaning under the first condition (FIG. 2), in which the side surface Ga is cleaned. In step S14, the inner DC voltage is maintained at 500 V from step S13, and the outer DC voltage is reduced from step S13, specifically to 300 V.

[0055] 7 also shows a cleaning cycle for the gap G. That is, in this embodiment, after performing the above-described steps S1 to S14, steps S14 to S1 are performed in reverse, and these steps S1 to S14 and S14 to S1 are repeated. Then, in the gap G, cleaning of the side surface Ga, upper surface Gb, and side surface Gc, and cleaning of the side surface Gc, upper surface Gb, and side surface Ga are repeated. Therefore, even if the deposit D removed from the gap G as shown in FIG. 6 re-adheres to the gap G, the deposit D can be properly removed.

[0056] In the cleaning cycle of this embodiment, steps S1 to S14 and steps S14 to S1 are repeated, but the steps in the cleaning cycle are not limited to this. For example, steps S1 to S14 may be repeated after steps S1 to S14, i.e., steps S1 to S14 may be repeated.

[0057] 8 to 10, in cleaning the gap G, an auxiliary gas A (white arrow in the figure) may be supplied to the gap G. Fig. 8 is an explanatory diagram of the first cleaning (Fig. 2) performed under the first condition, Fig. 9 is an explanatory diagram of the second cleaning (Fig. 3) performed under the second condition, and Fig. 10 is an explanatory diagram of the third cleaning (Fig. 4) performed under the third condition.

[0058] The auxiliary gas A is supplied to the upper surface Gb of the gap G from the gas supply unit 20, for example, and flows from top to bottom within the gap G. The auxiliary gas A is also supplied during at least one of the first cleaning ( FIG. 8 ), second cleaning ( FIG. 9 ), and third cleaning ( FIG. 10 ). The auxiliary gas A then discharges the deposits D removed from the gap G downward and further discharges them from the gas discharge port 10 e. Therefore, the deposits D can be prevented from re-adhering to the gap G as described above.

[0059] The type of auxiliary gas A is not particularly limited, but is preferably the same as the cleaning gas. For example, an inert gas may be used as the auxiliary gas A. However, in this case, the concentration of the cleaning gas in the plasma processing chamber 10 may be reduced, which may result in a decrease in plasma generation efficiency. In this regard, using the same type of gas as the cleaning gas as the auxiliary gas A allows for efficient plasma generation.

[0060] In addition, in this embodiment, the auxiliary gas A is supplied to the gap G from above toward below, but the supply direction is not limited to this. For example, the auxiliary gas A may be supplied to the gap G from below toward above.

[0061] In the above embodiment, both the inner DC voltage and the outer DC voltage are varied to control the thickness da of the inner sheath Sa and the thickness db of the outer sheath Sb, but one of the DC voltages may be fixed and the other may be varied. Even in this case, the sheath thickness ratio da / db can be controlled, and as a result, the incident direction of ions into the gap G can be controlled.

[0062] In the above embodiment, when controlling the thickness da of the inner sheath Sa and the thickness db of the outer sheath Sb, both the inner DC voltage and the outer DC voltage are varied to control the self-bias voltages of the inner upper electrode 130 and the outer upper electrode 131. However, this is not limiting. For example, when bias RF power from the second RF generator 31b is supplied to the inner upper electrode 130 and the outer upper electrode 131, the bias RF power may be controlled to control the self-bias voltages of the inner upper electrode 130 and the outer upper electrode 131.

[0063] Furthermore, according to the above-mentioned equation (1) for calculating the thickness of the plasma sheath, when the plasma density is high, the sheath thickness becomes small, and when the plasma density is low, the sheath thickness becomes large. Therefore, the thickness da of the inner sheath Sa and the thickness db of the outer sheath Sb may be controlled by controlling the density of the plasma formed below the inner upper electrode 130 and the density of the plasma formed below the outer upper electrode 131.

[0064] For example, when source RF power from the first RF generating unit 31a is supplied to the inner upper electrode 130 and the outer upper electrode 131, the plasma density below the inner upper electrode 130 and the plasma density below the outer upper electrode 131 may be controlled by controlling these source RF powers.

[0065] Furthermore, for example, in order to control the plasma density, an electromagnet may be provided on the upper surface of the plasma processing chamber 10 to form a magnetic field in the plasma processing space 10s. In such a case, the plasma density below the inner upper electrode 130 and the plasma density below the outer upper electrode 131 may be controlled by controlling the magnetic field formed by the electromagnet above the inner upper electrode 130 and the magnetic field formed by the electromagnet above the outer upper electrode 131.

[0066] [Cleaning of Substrate Support Portion] The cleaning method of the above embodiment can also be applied to cleaning the minute gap F formed between the electrostatic chuck 1111 and the edge ring 113. Fig. 11 is an explanatory diagram showing how the gap F is cleaned in a state where a dummy substrate Wd is supported by the substrate support portion 11, and Fig. 12 is an explanatory diagram showing how the gap F is cleaned in a state where the dummy substrate is not supported by the substrate support portion 11 (substrate-less dry cleaning).

[0067] 11 and 12 , the electrostatic chuck 1111 has a central region 111a for supporting a dummy substrate Wd and an annular region 111b for supporting the ring assembly 112 (edge ​​ring 113). The central region 111a protrudes from the annular region 111b. A gap F is formed between the outer surface of the electrostatic chuck 1111 corresponding to the central region 111a and the inner surface of the edge ring 113. In the following description, the sheath of plasma generated above the electrostatic chuck 1111 is referred to as an inner sheath Sc, and the sheath of plasma generated above the edge ring 113 is referred to as an outer sheath Sd. The thickness dc of the inner sheath Sc is the distance from the plasma to the upper surface of the dummy substrate Wd (electrostatic chuck 1111), and the thickness dd of the outer sheath Sd is the distance from the plasma to the upper surface of the edge ring 113.

[0068] In cleaning the gap F, the self-bias voltage is also controlled to control the thickness dc of the inner sheath Sc and the thickness dd of the outer sheath Sd, thereby controlling the direction of incidence of ions into the gap F. That is, the DC voltage (hereinafter referred to as the "chuck DC voltage") applied to the electrostatic chuck 1111 from the third DC generator 32c is controlled to control the self-bias voltage of the dummy substrate Wd or the electrostatic chuck 1111. Furthermore, the DC voltage (hereinafter referred to as the "ring DC voltage") applied to the edge ring 113 from the fourth DC generator 32d is controlled to control the self-bias voltage of the edge ring 113.

[0069] 11A and 12A are explanatory diagrams illustrating a case where the chuck DC voltage is greater than the ring DC voltage. In the following description, this cleaning condition is referred to as the fourth condition. In this case, the thickness dc of the inner sheath Sc is greater than the thickness dd of the outer sheath Sd. As a result, the incident direction of ions into the gap F (indicated by the arrow in the figure) is tilted from the vertical toward the electrostatic chuck 1111, and ions are incident on the side surface Fa of the gap F on the inner upper electrode 130 side. This side surface Fa then becomes the cleaning target area, and deposits D attached to the side surface Fa are removed by the ions. Furthermore, in this case, the tilt angle of the ions increases as the sheath thickness ratio dc / dd increases.

[0070] 11(b) and 12(b) are explanatory diagrams illustrating the case where the chuck DC voltage and the ring DC voltage are the same. In the following description, this cleaning condition is referred to as the fifth condition. In this case, the thickness dc of the inner sheath Sc and the thickness dd of the outer sheath Sd are the same. In this case, the incident direction of ions into the gap F (arrow in the figure) becomes vertical, and ions are incident on the lower surface Fb of the gap F. This lower surface Fb then becomes the area to be cleaned, and deposits D attached to the lower surface Fb are removed by the ions.

[0071] 11(c) and 12(c) are explanatory diagrams illustrating a case where the chuck DC voltage is smaller than the ring DC voltage. In the following description, this cleaning condition is referred to as the sixth condition. In this case, the thickness dc of the inner sheath Sc is smaller than the thickness dd of the outer sheath Sd. As a result, the incident direction of ions into the gap F (indicated by the arrow in the figure) is tilted from the vertical toward the edge ring 113, and ions are incident on the side surface Fc of the gap F facing the edge ring 113. This side surface Fc then becomes the area to be cleaned, and deposits D adhering to this side surface Fc are removed by the ions. Furthermore, in this case, when the sheath thickness ratio dc / dd is small, the tilt angle of the ions becomes large.

[0072] In this embodiment, a fourth cleaning under the fourth condition (FIGS. 11(a) and 12(b)), a fifth cleaning under the fifth condition (FIGS. 11(a) and 12(b)), and a sixth cleaning under the sixth condition (FIGS. 11(a) and 12(b)) are performed sequentially. In this case, the side surface Fa, the lower surface Fb, and the side surface Fc in the gap F can be cleaned sequentially. Furthermore, by repeatedly performing the fourth cleaning, the fifth cleaning, and the sixth cleaning, cleaning of the side surface Fa, the lower surface Fb, and the side surface Fc, the lower surface Fb, and the side surface Fa in the gap F can be repeatedly performed. This makes it possible to suppress adhesion of the deposits D to the gap F and improve cleaning efficiency.

[0073] In this embodiment, both the chuck DC voltage and the ring DC voltage are varied to control the thickness dc of the inner sheath Sc and the thickness dd of the outer sheath Sd, but it is also possible to fix one of the DC voltages and vary the other. Even in this case, it is possible to control the sheath thickness ratio dc / dd, and as a result, it is possible to control the direction of ion incidence into the gap F.

[0074] In the above embodiment, cleaning of the gap G between the inner upper electrode 130 and the outer upper electrode 131 and cleaning of the gap F between the electrostatic chuck 1111 and the edge ring 113 may be performed separately, or both may be performed simultaneously.

[0075] Furthermore, the above-described cleanings (e.g., the fourth to sixth cleanings) may be performed on the gap formed between the edge ring 113 and the cover ring 114. In this case, the sheath of plasma generated above the edge ring 113 is referred to as the inner sheath, and the sheath of plasma generated above the cover ring 114 is referred to as the outer sheath. Because a DC voltage is applied only to the edge ring 113, only the thickness of the inner sheath above the edge ring 113 is variable. However, by varying the thickness ratio between the inner sheath and the outer sheath, the same effect as in the above embodiment can be obtained on the gap formed between the edge ring 113 and the cover ring 114.

[0076] Furthermore, in the showerhead assembly 13, the above-described cleanings (e.g., the first to third cleanings) may be performed on the gap formed between the upper electrode and an insulating ring (not shown) disposed around the outer periphery of the upper electrode. In this case, the sheath of the plasma generated below the upper electrode is referred to as the inner sheath, and the sheath of the plasma generated below the insulating ring is referred to as the outer sheath. Because a DC voltage is applied only to the upper electrode, only the thickness of the inner sheath below the upper electrode is variable. However, by varying the thickness ratio between the inner sheath and the outer sheath, the same effect as in the above embodiment can be obtained for the gap formed between the upper electrode and the insulating ring.

[0077] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims. For example, the components of the above-described embodiments may be arbitrarily combined. Such an arbitrary combination naturally provides the functions and effects of each of the components involved in the combination, and also provides other functions and effects that are apparent to those skilled in the art from the description of this specification.

[0078] Furthermore, the effects described herein are merely descriptive or exemplary and are not limiting. In other words, the technology according to the present disclosure may achieve other effects that are apparent to those skilled in the art from the description of this specification, in addition to or in place of the above-described effects.

[0079] Note that the following configuration examples also fall within the technical scope of the present disclosure: (1) A method for cleaning a plasma processing apparatus, comprising: (a) introducing a cleaning gas into a chamber of the plasma processing apparatus; (b) generating plasma in the chamber under first conditions to perform a first cleaning; and (c) generating plasma in the chamber under second conditions to perform a second cleaning, wherein at least one of the first condition and the second condition is adjusted so that a first ratio of an inner sheath thickness to an outer sheath thickness in a sheath of the plasma generated in the step (b) differs from a second ratio of an inner sheath thickness to an outer sheath thickness in a sheath of the plasma generated in the step (c). (2) The method for cleaning a plasma processing apparatus according to (1), wherein the steps (b) and (c) are repeatedly performed. (3) The method for cleaning a plasma processing apparatus according to (1) or (2), comprising: (d) a step of switching from the step (b) to the step (c), wherein the thickness of the plasma sheath is varied in stages from the first ratio to the second ratio. (4) The method for cleaning a plasma processing apparatus according to any one of (1) to (3), comprising: (e) a step of switching from the step (c) to the step (b), wherein the thickness of the plasma sheath is varied in stages from the second ratio to the first ratio. (5) The method for cleaning a plasma processing apparatus according to any one of (1) to (4), wherein the first cleaning in the step (b) and the second cleaning in the step (c) are performed on a gap between an inner upper electrode and an outer upper electrode in the plasma processing apparatus. (6) The method for cleaning a plasma processing apparatus according to (5), wherein the adjustment of at least one of the first condition and the second condition is performed by controlling a self-bias voltage of at least one of the inner upper electrode and the outer upper electrode. (7) The method for cleaning a plasma processing apparatus described in (6) above, wherein the adjustment of at least one of the first condition and the second condition is performed by controlling a DC voltage applied to at least one of the inner upper electrode and the outer upper electrode.(8) The method for cleaning a plasma processing apparatus according to (5), wherein the adjustment of at least one of the first condition and the second condition is performed by controlling the plasma density below at least one of the inner upper electrode and the outer upper electrode. (9) The plasma processing apparatus according to any of (5) to (8), wherein an auxiliary gas is supplied to the gap in at least one of the steps (b) and (c). (10) The method for cleaning a plasma processing apparatus according to (9), wherein the auxiliary gas is the same type of gas as the cleaning gas. (11) The method for cleaning a plasma processing apparatus according to any of (1) to (4), wherein the first cleaning in the step (b) and the second cleaning in the step (c) are performed on a gap between an electrostatic chuck and an edge ring in the plasma processing apparatus. (12) The method for cleaning a plasma processing apparatus according to any of (1) to (4), wherein the first cleaning in the step (b) and the second cleaning in the step (c) are performed on a gap between an edge ring and a cover ring in the plasma processing apparatus. (13) A cleaning method for a plasma processing apparatus described in any one of (1) to (4), wherein the first cleaning in step (b) and the second cleaning in step (c) are performed on the gap between an upper electrode in the plasma processing apparatus and an insulating ring installed on the outer periphery of the upper electrode.

[0080] REFERENCE SIGNS LIST 1 plasma processing apparatus 2 control unit 10 plasma processing chamber 20 gas supply unit 31 RF power supply W substrate

Claims

1. A method for cleaning a plasma processing apparatus, comprising: (a) a step of introducing a cleaning gas into a chamber of the plasma processing apparatus; (b) a step of generating plasma in the chamber under first conditions to perform a first cleaning; and (c) a step of generating plasma in the chamber under second conditions to perform a second cleaning, wherein at least one of the first condition and the second condition is adjusted so that a first ratio of a thickness of an inner sheath to a thickness of an outer sheath in the sheath of the plasma generated in the step (b) is different from a second ratio of a thickness of the inner sheath to a thickness of an outer sheath in the sheath of the plasma generated in the step (c).

2. The method for cleaning a plasma processing apparatus according to claim 1, wherein steps (b) and (c) are repeated.

3. A cleaning method for a plasma processing apparatus as described in claim 1 or 2, comprising: (d) a step of switching from step (b) to step (c), which includes a step of gradually changing the thickness of the plasma sheath from the first ratio to the second ratio.

4. A cleaning method for a plasma processing apparatus as described in claim 1 or 2, comprising: (e) a step of switching from step (c) to step (b), which includes a step of gradually changing the thickness of the plasma sheath from the second ratio to the first ratio.

5. A cleaning method for a plasma processing apparatus as described in claim 1 or 2, wherein the first cleaning in step (b) and the second cleaning in step (c) are performed on the gap between an inner upper electrode and an outer upper electrode in the plasma processing apparatus.

6. A method for cleaning a plasma processing apparatus as described in claim 5, wherein adjustment of at least one of the first condition and the second condition is performed by controlling the self-bias voltage of at least one of the inner upper electrode and the outer upper electrode.

7. A method for cleaning a plasma processing apparatus as described in claim 6, wherein adjustment of at least one of the first condition and the second condition is performed by controlling a DC voltage applied to at least one of the inner upper electrode and the outer upper electrode.

8. A method for cleaning a plasma processing apparatus as described in claim 5, wherein adjustment of at least one of the first condition and the second condition is performed by controlling plasma density below at least one of the inner upper electrode and the outer upper electrode.

9. The method for cleaning a plasma processing apparatus according to claim 5, wherein an auxiliary gas is supplied to the gap in at least one of the steps (b) and (c).

10. The method for cleaning a plasma processing apparatus according to claim 9, wherein the auxiliary gas is the same type of gas as the cleaning gas.

11. A method for cleaning a plasma processing apparatus as described in claim 1 or 2, wherein the first cleaning in step (b) and the second cleaning in step (c) are performed on a gap between an electrostatic chuck and an edge ring in the plasma processing apparatus.

12. A method for cleaning a plasma processing apparatus as described in claim 1 or 2, wherein the first cleaning in step (b) and the second cleaning in step (c) are performed on a gap between an edge ring and a cover ring in the plasma processing apparatus.

13. A cleaning method for a plasma processing apparatus as described in claim 1 or 2, wherein the first cleaning in step (b) and the second cleaning in step (c) are performed on the gap between an upper electrode in the plasma processing apparatus and an insulating ring installed on the outer periphery of the upper electrode.

14. A plasma processing apparatus comprising: a chamber; a gas supply unit for supplying a cleaning gas into the chamber; a plasma generation unit for generating plasma from the cleaning gas in the chamber; and a control unit, wherein the control unit controls the gas supply unit and the plasma generation unit to perform the following steps: (a) a step of introducing the cleaning gas into the chamber; (b) a step of generating plasma in the chamber under first conditions to perform a first cleaning; and (c) a step of generating plasma in the chamber under second conditions to perform a second cleaning; and adjusts at least one of the first condition and the second condition so that a first ratio of an inner sheath thickness to an outer sheath thickness in a sheath of the plasma generated in the step (b) is different from a second ratio of an inner sheath thickness to an outer sheath thickness in a sheath of the plasma generated in the step (c).

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