Plasma treatment method and plasma treatment system

Abstract

To appropriately pre-coating the surface of a member inside a chamber prior to plasma processing.SOLUTION: A plasma processing method includes a step (a) of forming a first protective film on a surface of a member inside a chamber with a first process gas including a halogen-free precursor gas, and a step (b) of plasma-processing an object to be processed carried into the chamber with plasma of a second processing gas after the first protective film is formed on the surface of the member.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a plasma processing method for etching a silicon-containing film. Such a plasma processing method includes a step of coating the inside of a chamber with a carbon film, and a step of supplying a gas containing a fluorocarbon-containing gas into the chamber after the coating and etching the silicon-containing film with the generated plasma.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The technology according to the present disclosure appropriately performs pre-coating on the surface of the members inside the chamber before plasma processing.

Means for Solving the Problems

[0005] A plasma processing method according to an aspect of the present disclosure includes: (a) a step of forming a first protective film on the surface of a member inside a chamber with a first processing gas containing a precursor gas not containing halogen; and (b) a step of plasma-processing a processing object carried into the chamber with the plasma of a second processing gas after the first protective film is formed on the surface of the member.

Effects of the Invention

[0006] According to this disclosure, pre-coating can be appropriately performed on the surface of the components inside the chamber before plasma treatment. [Brief explanation of the drawing]

[0007] [Figure 1] This is a diagram illustrating an example configuration of a plasma processing system. [Figure 2] This is a diagram illustrating an example configuration of a capacitively coupled plasma processing apparatus. [Figure 3] This is a flowchart showing the main steps of the plasma treatment according to the first embodiment. [Figure 4] This diagram illustrates the surface state of the chamber internal members in Comparative Examples 1 and 2 of the first embodiment. [Figure 5] This is a diagram illustrating the surface state of the chamber internal member in an embodiment of the first embodiment. [Figure 6] This is a flowchart showing the main steps of the plasma treatment according to the second embodiment. [Figure 7] This figure illustrates the pre-coating of the first protective film and the second protective film in the second embodiment. [Figure 8A] This is a diagram illustrating the film thickness of the first protective film in the second embodiment. [Figure 8B] This is a diagram illustrating the film thickness of the first protective film in the second embodiment. [Figure 8C] This is a diagram illustrating the film thickness of the first protective film in the second embodiment. [Figure 9A] This is a diagram illustrating the film thickness of the first protective film in the first embodiment. [Figure 9B] This is a diagram illustrating the film thickness of the first protective film in the first embodiment. [Modes for carrying out the invention]

[0008] In the semiconductor device manufacturing process, plasma processing such as etching and film deposition is performed on a semiconductor substrate (hereinafter referred to as "substrate") in a plasma processing apparatus. In the plasma processing apparatus, plasma is generated by exciting a processing gas inside the chamber, and the substrate is processed with this plasma.

[0009] Before plasma treatment, a so-called pre-coating is performed on the surface of the components inside the chamber (hereinafter sometimes referred to as "chamber components"). Pre-coating is performed by coating the surface of the chamber components with a protective film in order to stabilize the plasma treatment or to suppress wear of the chamber components during plasma treatment. As this pre-coating, for example, in the plasma treatment method described in Patent Document 1 above, the inside of the chamber is coated with a carbon film.

[0010] The pre-coating protective film is removed after a certain period of plasma treatment, and a new protective film is then applied to the surface of the chamber's internal components. In other words, the pre-coating of the protective film, plasma treatment, and removal of the protective film are repeated, and the plasma treatment continues.

[0011] However, after diligent investigation by the inventors, it was found that depending on the type of protective film used for pre-coating, the results of the plasma treatment may shift, causing the plasma treatment rate to change over time. Furthermore, when the chamber components were examined in cases where the plasma treatment results shifted in this way, it was confirmed that the chamber components were damaged. Therefore, there is room for improvement in conventional pre-coating before plasma treatment.

[0012] The technology according to the present disclosure has been made in view of the above circumstances, and appropriately performs pre - coating on the surface of the members inside the chamber before plasma treatment. Hereinafter, the plasma treatment system and the plasma treatment method according to the present embodiment will be described with reference to the drawings. In the present specification and drawings, elements having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

[0013] <Plasma treatment system> First, a plasma treatment system according to an embodiment will be described. FIG. 1 is a diagram for explaining a configuration example of the plasma treatment system.

[0014] In one embodiment, the plasma treatment system includes a plasma treatment apparatus 1 and a control unit 2. The plasma treatment system is an example of a substrate treatment system, and the plasma treatment apparatus 1 is an example of a substrate treatment apparatus. The plasma treatment apparatus 1 includes a plasma treatment chamber 10, a substrate support portion 11, and a plasma generation portion 12. The plasma treatment chamber 10 has a plasma treatment space. Further, the plasma treatment chamber 10 has at least one gas supply port for supplying at least one processing gas to the plasma treatment space and at least one gas discharge port for discharging gas from the plasma treatment space. The gas supply port is connected to a gas supply unit 20 described later, and the gas discharge port is connected to an exhaust system 40 described later. The substrate support portion 11 is disposed in the plasma treatment space and has a substrate support surface for supporting a substrate.

[0015] The plasma generation unit 12 is configured to generate plasma from at least one processing gas supplied into the plasma processing space. The plasma formed in the plasma processing space may be a capacitively coupled plasma (CCP), an inductively coupled plasma (ICP), an electron-cyclotron-resonance plasma (ECR), a helicon wave-excited plasma (HWP), or a surface wave plasma (SWP), etc. Various types of plasma generation units, including an AC (Alternating Current) plasma generation unit and a DC (Direct Current) plasma generation unit, may also be used. In one embodiment, the AC signal (AC power) used in the AC plasma generation unit has a frequency in the range of 100 kHz to 10 GHz. Therefore, the AC signal includes an RF (Radio Frequency) signal and a microwave signal. In one embodiment, the RF signal has a frequency in the range of 100 kHz to 150 MHz.

[0016] The control unit 2 processes computer-executable instructions that cause the plasma processing apparatus 1 to execute various processes described in the present disclosure. The control unit 2 can be configured to control each element of the plasma processing apparatus 1 to execute the 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 is realized by, for example, a computer 2a. The processing unit 2a1 can be configured to perform various control operations by reading a program from the storage unit 2a2 and executing the read program. This program may be stored in the storage unit 2a2 in advance, or may be acquired via a medium when necessary. The acquired program is stored in the storage unit 2a2 and read from the storage unit 2a2 by the processing unit 2a1 and executed. The medium may be various storage media readable by the computer 2a, or may be 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 RAM (Random Access Memory), a ROM (Read Only Memory), a HDD (Hard Disk Drive), an SSD (Solid State Drive), or a combination thereof. The communication interface 2a3 may communicate with the plasma processing apparatus 1 via a communication line such as a LAN (Local Area Network).

[0017] <Plasma Processing Apparatus> Hereinafter, a configuration example of a capacitively coupled plasma processing apparatus as an example of the plasma processing apparatus 1 will be described. FIG. 2 is a diagram for explaining a configuration example of a capacitively coupled plasma processing apparatus.

[0018] 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 unit 11 and a gas introduction unit. The gas introduction unit is configured to introduce at least one processing gas into the plasma processing chamber 10. The gas introduction unit includes a shower head 13. The substrate support unit 11 is located inside the plasma processing chamber 10. The shower head 13 is located above the substrate support unit 11. In one embodiment, the shower head 13 constitutes at least a portion of the ceiling of the plasma processing chamber 10. The plasma processing chamber 10 has a plasma processing space 10s defined by the shower head 13, the side walls 10a of the plasma processing chamber 10, and the substrate support unit 11. The plasma processing chamber 10 is grounded. The shower head 13 and the substrate support unit 11 are electrically insulated from the housing of the plasma processing chamber 10.

[0019] The substrate support portion 11 includes a main body portion 111 and a ring assembly 112. The main body portion 111 has a central region 111a for supporting the substrate W as the object to be processed, and an annular region 111b for supporting the ring assembly 112. A wafer is an example of the substrate W. The annular region 111b of the main body portion 111 surrounds the central region 111a of the main body portion 111 in a plan view. The substrate W is placed on the central region 111a of the main body portion 111, and the ring assembly 112 is placed on the annular region 111b of the main body portion 111 so as to surround the substrate W on the central region 111a of the main body portion 111. Therefore, the central region 111a is also called the substrate support surface for supporting the substrate W, and the annular region 111b is also called the ring support surface for supporting the ring assembly 112.

[0020] 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 placed on the base 1110. The electrostatic chuck 1111 includes a ceramic member 1111a and an electrostatic electrode 1111b placed 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. Other members surrounding the electrostatic chuck 1111, such as an annular electrostatic chuck or an annular insulating member, may also have an annular region 111b. In this case, the ring assembly 112 may be placed on the annular electrostatic chuck or the annular insulating member, or on both the electrostatic chuck 1111 and the annular insulating member. Furthermore, at least one RF / DC electrode, coupled to the RF power supply 31 and / or DC power supply 32 described later, may be placed within the ceramic member 1111a. In this case, at least one RF / DC electrode functions as a lower electrode. When a bias RF signal and / or DC signal, described later, is supplied to 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 at least one RF / DC electrode may function as multiple lower electrodes. Also, the electrostatic electrode 1111b may function as a lower electrode. Therefore, the substrate support portion 11 includes at least one lower electrode.

[0021] 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 covering ring. The edge rings are formed of a conductive or insulating material, and the covering rings are formed of an insulating material.

[0022] The substrate support section 11 may also include a temperature control 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 control module may include a heater, a heat transfer medium, a flow path 1110a, or a combination thereof. A heat transfer fluid, such as brine or gas, flows through the flow path 1110a. In one embodiment, the flow path 1110a is formed within the base 1110, and one or more heaters are arranged within the ceramic member 1111a of the electrostatic chuck 1111. The substrate support section 11 may also include a heat transfer gas supply section configured to supply heat transfer gas to the gap between the back surface of the substrate W and the central region 111a.

[0023] The showerhead 13 is configured to introduce at least one processing gas from the gas supply unit 20 into the plasma processing space 10s. The showerhead 13 has at least one gas supply port 13a, at least one gas diffusion chamber 13b, and a plurality of gas inlet ports 13c. The processing gas supplied to the gas supply port 13a passes through the gas diffusion chamber 13b and is introduced into the plasma processing space 10s through the plurality of gas inlet ports 13c. The showerhead 13 also includes at least one upper electrode. In addition to the showerhead 13, the gas introduction unit may also include one or more side gas injectors (SGIs) attached to one or more openings formed in the side wall 10a.

[0024] 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 processing gas to the shower head 13 from a corresponding gas source 21 via a corresponding flow controller 22. Each flow controller 22 may include, for example, a mass flow controller or a pressure-controlled flow controller. Furthermore, the gas supply unit 20 may include at least one flow modulation device that modulates or pulses the flow rate of at least one processing gas.

[0025] 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. This causes plasma to be formed from at least one processing gas supplied to the plasma processing space 10s. Thus, the RF power supply 31 can function as at least part of the plasma generation unit 12. In addition, by supplying a bias RF signal to at least one lower electrode, a bias potential is generated on the substrate W, and ionic components in the formed plasma can be drawn into the substrate W.

[0026] In one embodiment, the RF power supply 31 includes a first RF generation unit 31a and a second RF generation unit 31b. The first RF generation unit 31a is coupled to at least one lower electrode and / or at least one upper electrode 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 generation unit 31a may be configured to generate a plurality of source RF signals having different frequencies. One or more generated source RF signals are supplied to at least one lower electrode and / or at least one upper electrode.

[0027] The second RF generation unit 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 generation unit 31b may be configured to generate a plurality of bias RF signals having different frequencies. One or more generated 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.

[0028] 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 generation unit 32a and a second DC generation unit 32b. In one embodiment, the first DC generation unit 32a is connected to at least one lower electrode and configured to generate a first DC signal. The generated first DC signal is applied to at least one lower electrode. In one embodiment, the second DC generation unit 32b is connected to at least one upper electrode and configured to generate a second DC signal. The generated second DC signal is applied to at least one upper electrode.

[0029] In various embodiments, the first and second DC signals may be pulsed. In this case, a sequence of voltage pulses is applied to at least one lower electrode and / or at least one upper electrode. The voltage pulses may have a rectangular, trapezoidal, triangular, or a combination thereof pulse waveform. In one embodiment, a waveform generation unit for generating a sequence of voltage pulses from the DC signal is connected between the first DC generation unit 32a and at least one lower electrode. Thus, the first DC generation unit 32a and the waveform generation unit constitute a voltage pulse generation unit. When the second DC generation unit 32b and the waveform generation unit constitute a voltage pulse generation unit, the voltage pulse generation unit is connected to at least one upper electrode. The voltage pulses may have positive or negative polarity. The sequence of voltage pulses may also include one or more positive voltage pulses and one or more negative voltage pulses within one period. The first and second DC generation units 32a and 32b may be provided in addition to the RF power supply 31, and the first DC generation unit 32a may be provided in place of the second RF generation unit 31b.

[0030] The exhaust system 40 may be connected to, for example, a gas outlet 10e located 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 regulating valve regulates the pressure in the plasma processing space 10s. The vacuum pump may include a turbomolecular pump, a dry pump, or a combination thereof.

[0031] <First Embodiment of Plasma Treatment Method> Next, a first embodiment of the plasma processing method will be described. In the first embodiment, the case in which etching is performed as the plasma processing will be described. Figure 3 is a flowchart showing the main steps of the plasma processing according to the first embodiment.

[0032] [Step S1] First, a so-called pre-coating is performed, in which a first protective film is formed on the surface of the components inside the plasma processing chamber 10 (hereinafter sometimes referred to as "in-chamber components") using the plasma of the first processing gas (step S1 in Figure 3). The in-chamber components include at least components exposed to the plasma processing space 10s, and also include the plasma processing chamber 10. The in-chamber components also include components formed from materials such as Si or quartz. The first processing gas includes a halogen-free precursor gas. The precursor gas is a hydrocarbon gas (CxHy: x, y is an integer), such as CH4, C2H6, C2H4, C3H8, C3H6, etc. The first processing gas may also contain a noble gas. Examples of noble gases include Ar and He.

[0033] In step S1, first, a substrate different from the object to be processed (hereinafter referred to as the "dummy substrate") is brought into the plasma processing chamber 10 and placed on the electrostatic chuck 1111. After the dummy substrate is brought in, the inside of the plasma processing chamber 10 is depressurized to the desired vacuum level by the exhaust system 40.

[0034] Next, the first processing gas is supplied from the gas supply unit 20 to the plasma processing space 10s via the shower head 13. The first RF generation unit 31a of the RF power supply 31 supplies source RF power for plasma generation to the conductive member of the substrate support unit 11 and / or the conductive member of the shower head 13. This first processing gas is excited to generate plasma. The generated plasma then forms a first protective film on the surface of the chamber's internal components. After the formation of the first protective film, the dummy substrate is removed from the plasma processing chamber 10.

[0035] [Step S2] Next, the substrate W, which is the object to be processed, is etched by plasma of a second processing gas (step S2 in Figure 3). The second processing gas contains at least a hydrogen-containing gas. Examples of hydrogen-containing gases include HBr, CH2F2, and H2. The second processing gas may also contain fluorocarbon gases or hydrofluorocarbon gases, and may contain halogen-containing gases. Examples of fluorocarbon gases include C4F6 and C4F8, examples of hydrofluorocarbon gases include CHF3 and CH2F2, and examples of halogen-containing gases include Cl2 and SiCl4. The second processing gas may also contain metal-containing gases such as WF6. Furthermore, the second processing gas may contain noble gases, oxygen-containing gases, and nitrogen-containing gases. Examples of noble gases include Ar and He, examples of oxygen-containing gases include O2, and examples of nitrogen-containing gases include N2. These second processing gases are selected depending on the film to be etched contained in the substrate W and the desired shape of the film to be etched after etching.

[0036] In step S2, first, the substrate W, which is to be processed, is brought into the plasma processing chamber 10 and placed on the electrostatic chuck 1111. The substrate W is held by electrostatic attraction to the electrostatic chuck 1111 by Coulomb force. At this time, the substrate W is adjusted to the desired temperature. After the substrate W is brought in, the inside of the plasma processing chamber 10 is depressurized to the desired vacuum level by the exhaust system 40.

[0037] Next, a second processing gas is supplied from the gas supply unit 20 to the plasma processing space 10s via the shower head 13. The first RF generation unit 31a of the RF power supply 31 supplies source RF power for plasma generation to the conductive member of the substrate support unit 11 and / or the conductive member of the shower head 13. This second processing gas is excited to generate plasma. At this time, the second RF generation unit 31b may supply a bias RF signal for ion pull. The generated plasma then etches the substrate W. After etching, the substrate W is removed from the plasma processing chamber 10.

[0038] In step S2, the substrate W to be etched may be one or multiple substrates. If multiple substrates are used, after the etched substrates W are removed from the plasma processing chamber 10, another substrate W is brought into the plasma processing chamber 10 and etched.

[0039] [Step S3] Next, the first protective film is removed from the surface of the chamber-internal component by plasma of a third processing gas containing a gas capable of removing the first protective film (step S3 in Figure 3). The gas capable of removing the first protective film is an oxygen-containing gas. An oxygen-containing gas is, for example, O2.

[0040] In step S3, first, a dummy substrate is brought into the plasma processing chamber 10 and placed on the electrostatic chuck 1111. After the dummy substrate is brought in, the inside of the plasma processing chamber 10 is depressurized to the desired vacuum level by the exhaust system 40.

[0041] Next, a third processing gas is supplied from the gas supply unit 20 to the plasma processing space 10s via the shower head 13. The first RF generation unit 31a of the RF power supply 31 supplies source RF power for plasma generation to the conductive member of the substrate support unit 11 and / or the conductive member of the shower head 13. This third processing gas is excited to generate plasma. At this time, the second RF generation unit 31b may supply a bias RF signal for ion pull. The generated plasma then removes the first protective film from the surface of the chamber internal member. After the removal of the first protective film, the dummy substrate is removed from the plasma processing chamber 10.

[0042] Furthermore, after the dummy substrate is removed from the plasma processing chamber 10, the surface of the chamber's internal components and the surface of the electrostatic chuck 1111 may be cleaned with the plasma of the third processing gas. At the same time, any charges accumulated on the surface of the electrostatic chuck 1111 can also be removed.

[0043] Furthermore, after the removal of the first protective film, before the dummy substrate is removed from the plasma processing chamber 10, the dummy substrate may be separated from the surface of the electrostatic chuck 1111, and the plasma of the third processing gas may be used to clean the surface of the chamber internal components and the surface of the electrostatic chuck 1111, and to remove any charges accumulated on the surface of the electrostatic chuck 1111. In this case, in order to generate sufficient plasma between the dummy substrate and the surface of the electrostatic chuck 1111, the distance at which the dummy substrate is separated from the surface of the electrostatic chuck 1111 is preferably greater than the sheath width formed by the plasma of the third processing gas, and preferably about 8 mm or more.

[0044] In the first embodiment, steps S1 to S3 are repeated, and plasma treatment of the substrate W is continuously performed.

[0045] Furthermore, if steps S1 to S3 are repeated, the dummy board used in step S1 and the dummy board used in step S3 may be the same. In this case, it becomes possible to omit the removal of the dummy board after step S3 and the loading of the dummy board at the start of step S1, thereby saving time.

[0046] According to the first embodiment described above, in step S1, a first protective film is formed on the surface of the chamber internal member by plasma of a first processing gas containing a halogen-free precursor gas. As a result, etching in step S2 is stabilized, and for example, changes in the etching rate over time can be suppressed. Furthermore, even if the first protective film is removed in step S3, damage to the chamber internal member can be suppressed. Details of these effects will be described below.

[0047] The inventors investigated the change in etching rate over time by etching a substrate W when different types of pre-coating were applied. Comparative Example 1 is an example in which a protective film was formed on the surface of a chamber internal component by plasma of C4F8 gas. Comparative Example 2 is an example in which a protective film was formed on the surface of a chamber internal component by plasma of a mixed gas of CH4 gas and C4F8 gas. The Example is an example of this embodiment, in which a first protective film was formed on the surface of a chamber internal component by plasma of CH4 gas.

[0048] Comparative Example 1 will now be described. In this experiment, the change in etching rate over time when the protective film of Comparative Example 1 was pre-coated with C4F8 single gas was compared with the change in etching rate over time when there was no pre-coating. As a result, in both the case with and without pre-coating of Comparative Example 1, the etching rate increased over time. Furthermore, the change in etching rate over time when Comparative Example 1 was pre-coated was greater than the change in etching rate over time when there was no pre-coating. For example, the change in etching rate over time was 1.4% when there was no pre-coating. On the other hand, the change in etching rate over time when Comparative Example 1 was pre-coated was 2.7%. Therefore, it was found that etching was unstable when the protective film of Comparative Example 1 was pre-coated with C4F8 single gas. Note that the change in etching rate over time is the rate of change in the etching rate after etching, i.e., supplying source RF power for a certain period of time (10h), compared to the initial (0h) etching rate.

[0049] Comparative Example 2 will now be described. In this experiment, the change in etching rate over time when a protective film was pre-coated with a mixed gas of CH4 and C4F8 in Comparative Example 2 was compared with the change in etching rate over time when there was no pre-coating. As a result, in both the case with and without pre-coating in Comparative Example 2, the etching rate increased over time. However, the change in etching rate over time when pre-coating was performed in Comparative Example 2 was about half that of the case without pre-coating. For example, the rate of change in etching rate over time when there was no pre-coating was 6.3%. On the other hand, when pre-coating was performed in Comparative Example 2, the rate of change in etching rate over time was 3.7%. Therefore, it was found that when a protective film was pre-coated with a mixed gas of CH4 and C4F8 in Comparative Example 2, the change in etching rate over time was improved compared to Comparative Example 1 described above, but the etching was still not stable.

[0050] The examples are described below. In this experiment, the change in etching rate over time was compared between the case where a protective film using CH4 gas as a single gas was pre-coated and the case where there was no pre-coating. As a result, the etching rate increased over time when there was no pre-coating, whereas when there was pre-coating as in the examples, the etching rate remained almost unchanged over time. For example, the rate of change in etching rate over time was 2.6% when there was no pre-coating. On the other hand, when there was pre-coating as in the examples, the rate of change in etching rate over time was 0.06%. Therefore, it was found that pre-coating the protective film using CH4 gas as a single gas as in the examples suppresses the change in etching rate over time and stabilizes etching.

[0051] From the experimental results above, it was found that pre-coating the protective film with CH4 gas as described in the example minimizes the change in etching rate over time. Furthermore, after diligent research by the inventors, it was discovered that pre-coating the first protective film with a first processing gas containing a halogen-free precursor gas also minimizes the change in etching rate over time and stabilizes etching, similar to the CH4 gas method.

[0052] As described above, the change in etching rate over time can be reduced in the following order: Example (CH4 single gas), Comparative Example 2 (mixed gas of CH4 gas and C4F8 gas), and Comparative Example 1 (C4F8 single gas). The inventors of the present invention have inferred the following mechanism.

[0053] As shown in Figure 4(a), in the case where the protective film R of Comparative Examples 1 and 2 contains F, the protective film R is exposed to H in the hydrogen-containing gas of the second processing gas used during etching. Then, as shown in Figure 4(b), F and H react inside the protective film R to generate HF, and this HF reacts with the chamber internal member M, damaging (wearing) the surface of the chamber internal member M and causing surface roughness. The chamber internal member M is formed of, for example, Si or quartz. The damage to the chamber internal member M affects etching, and the etching rate changes over time.

[0054] In contrast, as shown in Figure 5, if the first protective film P1 in the embodiment does not contain F (halogen), the first protective film P1 does not react with H in the second processing gas, thus suppressing damage to the surface of the chamber internal member M. As a result, changes in the etching rate over time can be suppressed, and etching can be stabilized.

[0055] Even if the second processing gas does not contain hydrogen, it is expected that at the interface between the chamber internal member M and the protective film R, the surface of the chamber internal member M may be damaged (worn) and surface roughened due to a reaction between the surface of the chamber internal member M and F contained in the protective film R, caused by thermal energy or the energy of ions irradiated from the plasma. Thermal energy may be obtained when the chamber internal member M is controlled to a constant temperature by a heating mechanism not described, or by heating with UV light from the plasma, or when the energy of ions irradiated from the plasma is converted into heat. In this regard, for example, if the first protective film P1 in the embodiment does not contain F (halogen), damage to the surface of the chamber internal member M can be suppressed.

[0056] <Second Embodiment of Plasma Treatment Method> Next, a second embodiment of the plasma processing method will be described. In the first embodiment described above, a first protective film, i.e., a single layer, was pre-coated, but in this second embodiment, multiple layers of protective film are pre-coated. In the second embodiment as well, the case in which etching is performed as the plasma processing will be described, similar to the first embodiment. Figure 6 is a flowchart showing the main steps of the plasma processing according to the second embodiment.

[0057] [Step T1] First, a so-called pre-coating is performed, in which a first protective film is formed on the surface of the chamber internal components using the plasma of the first processing gas (step T1 in Figure 6). The first processing gas contains a halogen-free precursor gas. The precursor gas is a hydrocarbon gas (CxHy: x, y is an integer), such as CH4, C2H6, C2H4, C3H8, C3H6, etc. The first processing gas may also contain a noble gas. The noble gas is, for example, Ar, He, etc. Note that the details of step T1 are the same as those of step S1 in the first embodiment described above, so the explanation is omitted.

[0058] [Step T2] Next, a so-called pre-coating is performed (step T2 in Figure 6) in which a second protective film P2 is formed on the first protective film P1 using plasma of a fourth processing gas of the same type as the second processing gas used in step T3 described later (as shown in Figure 7). The fourth processing gas contains the same precursor gas as the second processing gas. The fourth processing gas may contain, for example, one or more of H, F, N, and C. The fourth processing gas may also contain a metal-containing gas.

[0059] Step T2 is carried out with the dummy substrate still placed on the electrostatic chuck 1111, continuing from step T1. The processing gas supplied from the gas supply unit 20 to the plasma processing space 10s via the shower head 13 is switched from the first processing gas to the fourth processing gas. The first RF generation unit 31a of the RF power supply 31 supplies source RF power for plasma generation to the conductive member of the substrate support unit 11 and / or the conductive member of the shower head 13. This fourth processing gas is excited to generate plasma. At this time, the second RF generation unit 31b may supply a bias RF signal for ion pull. The generated plasma then forms a second protective film P2 on the first protective film P1. After the formation of the second protective film P2, the dummy substrate is removed from the plasma processing chamber 10.

[0060] The process conditions in step T2 are preferably the same as the process conditions in step T3, which will be described later. For example, if step T3 includes several different process conditions, and the substrate W is etched by sequentially performing process conditions A, B, and C, the process conditions in step T2 are preferably the same as the first process condition A in step T3.

[0061] In such cases, when etching is performed in step T3, by-products are generated by the etching, but the same by-products are generated from the second protective film P2. If the same by-products as those generated during etching are generated from the second protective film P2, the process conditions in step T2 do not need to be exactly the same as the initial process conditions A in step T3. For example, the following order of priority for setting the conditions can be considered: (1) to (3). (1) The type of the fourth treatment gas in step T2 is the same as the type of the second treatment gas in step T3. (2) The flow rate of the fourth process gas in step T2 is the same as the flow rate of the second process gas in step T3. (3) The RF power and processing pressure in step T2 are the same as the RF power and processing pressure in step T3, respectively.

[0062] [Step T3] Next, the substrate W, which is the object to be processed, is etched by the plasma of the second processing gas (step T3 in Figure 6). The substrate W to be etched may be one or multiple substrates. The details of step T3 are the same as those of step S2 in the first embodiment described above, so the explanation will be omitted.

[0063] [Step T4] Next, the second protective film P2 is removed from the first protective film P1 by plasma of a fifth processing gas containing a gas capable of removing the second protective film P2 (step T4 in Figure 6). The gas capable of removing the second protective film P2 is appropriately selected depending on the second protective film P2. For example, if the main component of the second protective film P2 is an organic film such as fluorocarbon, the gas capable of removing the second protective film P2 (the fifth processing gas) is an oxygen-containing gas. An oxygen-containing gas is, for example, O2. Also, if the second protective film P2 contains a metal, the fifth processing gas may contain a halogen-containing gas. An halogen-containing gas is, for example, CF4 gas or Cl2 gas.

[0064] In step T4, first, a dummy substrate is brought into the plasma processing chamber 10 and placed on the electrostatic chuck 1111. After the dummy substrate is brought in, the inside of the plasma processing chamber 10 is depressurized to the desired vacuum level by the exhaust system 40.

[0065] Next, a fifth processing gas is supplied from the gas supply unit 20 to the plasma processing space 10s via the shower head 13. The first RF generation unit 31a of the RF power supply 31 supplies source RF power for plasma generation to the conductive member of the substrate support unit 11 and / or the conductive member of the shower head 13. This fifth processing gas is excited to generate plasma. At this time, the second RF generation unit 31b may supply a bias RF signal for ion pull. The generated plasma then removes the second protective film P2 from the first protective film P1.

[0066] [Step T5] Next, the first protective film P1 is removed from the surface of the chamber member M by plasma of a third processing gas containing a gas capable of removing the first protective film P1 (step T5 in Figure 6). The gas capable of removing the first protective film P1 is an oxygen-containing gas. An oxygen-containing gas is, for example, O2. The details of step T5 are the same as those of step S3 in the first embodiment described above, so the explanation is omitted.

[0067] Furthermore, if the fifth processing gas in step T4 and the third processing gas in step T5 are the same, there is no need to separate steps T4 and T5, and the removal of the second protective film P2 and the removal of the first protective film P1 may be performed consecutively.

[0068] After the removal of the second protective film P2 and the first protective film, the dummy substrate is removed from the plasma processing chamber 10.

[0069] Furthermore, after the dummy substrate is removed from the plasma processing chamber 10, the surface of the chamber's internal components and the surface of the electrostatic chuck 1111 may be cleaned with the plasma of the third processing gas. At the same time, any charges accumulated on the surface of the electrostatic chuck 1111 can also be removed.

[0070] Furthermore, after the removal of the first protective film, before the dummy substrate is removed from the plasma processing chamber 10, the dummy substrate may be separated from the surface of the electrostatic chuck 1111, and the plasma of the third processing gas may be used to clean the surface of the chamber internal components and the surface of the electrostatic chuck 1111, and to remove any charges accumulated on the surface of the electrostatic chuck 1111. In this case, in order to generate sufficient plasma between the dummy substrate and the surface of the electrostatic chuck 1111, the distance at which the dummy substrate is separated from the surface of the electrostatic chuck 1111 is preferably greater than the sheath width formed by the plasma of the third processing gas, and preferably about 8 mm or more.

[0071] In the second embodiment, steps T1 to T5 are repeated, and plasma treatment of the substrate W is performed continuously.

[0072] Furthermore, if steps T1 to T5 are repeated, the dummy board used in step T1 and the dummy board used in steps T4 and T5 may be the same. In this case, it becomes possible to omit the removal of the dummy board after step T5 and the loading of the dummy board at the start of step T1, thereby saving time.

[0073] In the second embodiment described above, the same effects as in the first embodiment can be enjoyed. Specifically, in step T1, a first protective film P1 is formed on the surface of the chamber internal member M by plasma of a first processing gas containing a halogen-free precursor gas, so that etching in step T3 is stable and, for example, changes in the etching rate over time can be suppressed. Furthermore, even if the first protective film P1 is removed in step T5, damage to the chamber internal member M can be suppressed.

[0074] Furthermore, in the second embodiment, at least the type of the fourth processing gas in step T2 is the same as the type of the second processing gas in step T3, and preferably the process conditions in step T2 are the same as the initial process conditions A in step T3. Therefore, in step T3, the same byproducts as during etching can be generated from the second protective film P2. As a result, the etching in step T3 can be made even more stable. For example, when etching multiple substrates W in step T3, a constant etching rate is achieved from the first substrate. It is also possible to improve the in-plane uniformity of the etching rate. Furthermore, the rate of change of the etch rate after etching, i.e., supplying source RF power for a certain period of time, can also be reduced.

[0075] Furthermore, when etching the substrate W by sequentially performing process conditions D, E, and F in the second step T3, it is preferable that the process conditions in the second step T2 are the same as the first process condition D in step T3. In other words, it is preferable that the process conditions in step T2 are the same as the first process condition in step T3, which is performed immediately afterward.

[0076] Furthermore, in the second embodiment, although two layers, a first protective film P1 and a second protective film P2, were pre-coated in the above example, there may be three or more layers. In this case, the bottom layer on the chamber internal member M side may be the first protective film P1, and the top layer on the plasma processing space 10s side may be the second protective film P2. Also, the multiple pre-coating layers may change in the height direction like a gradient, and in this case as well, the bottom layer may be the first protective film P1 and the top layer may be the second protective film P2.

[0077] <Thickness of the first protective film> Next, the thickness of the first protective film P1 will be described. In step T4, the second protective film P2 is removed by so-called ion sputtering using the plasma of the fifth processing gas. In this case, as shown in Figure 8, ions generated by the plasma of the fifth processing gas (third processing gas) are irradiated onto the second protective film P2 and the first protective film P1.

[0078] As shown in Figure 8A, when the energy of the ions (hereinafter referred to as "ion energy") is large, that is, when the curved region in Figure 8A is large, the ion energy reaches the inside of the chamber member M (the hatched region in Figure 8). For example, if the second protective film P2 contains F and the chamber member M is made of Si, then Si and F react inside the surface layer of the chamber member M to produce SiF4, and then the SiF4 vaporizes. As a result, etching is promoted. Then, because this phenomenon of SiF4 vaporization occurs or does not occur within the surface of the chamber member M, the surface of the chamber member M is worn down and surface roughness occurs.

[0079] Furthermore, as shown in Figure 8B, even when ion energy reaches the surface of the chamber internal member M, the phenomenon of SiF4 vaporization occurs or does not occur within the surface of the chamber internal member M, resulting in roughness on the surface of the chamber internal member M.

[0080] In contrast, as shown in Figure 8C, if the ion energy does not reach the surface of the chamber internal member M, the phenomenon of SiF4 vaporization does not occur, and the surface of the chamber internal member M does not become rough. Therefore, it is preferable that the film thickness F of the first protective film P1 is thicker than the depth D to which the ions penetrate the first protective film P1 when the ions are irradiated onto the second protective film P2 and the first protective film P1 in step T4. In this case, surface roughness of the chamber internal member M can be suppressed.

[0081] In the first embodiment, only the first protective film P1 is pre-coated. Therefore, as shown in Figure 9A, the ion energy (curved region in Figure 9A) is large, and even if it reaches the interior of the surface layer of the chamber internal member M (hatched region in Figure 9A), the surface of the chamber internal member M is unlikely to react. However, the third processing gas used in step S3 may contain F, and there is a risk that the F in the third processing gas may reach the interior of the surface layer of the chamber internal member M. In such a case, as in Figure 8A above, Si and F will react and SiF4 will vaporize, which may cause roughness on the surface of the chamber internal member M.

[0082] Therefore, in the first embodiment as well, as shown in Figure 9B, it is preferable that the film thickness F of the first protective film P1 is thicker than the depth D to which the ions penetrate the first protective film P1 when the ions are irradiated onto the first protective film P1 in step S3. In this case, surface roughening of the chamber internal member M can be suppressed.

[0083] <Other Embodiments> In the first and second embodiments described above, the first protective film was an organic film and the precursor gas of the first processing gas was a hydrocarbon; however, the first protective film and precursor gas are not limited to these. For example, if the first protective film is an oxide film (SiO2 film), the precursor gas of the first processing gas does not need to contain halogens and may be a silicon-containing gas. Silicon-containing gases include aminosilane gases and silicon alkoxide gases. Examples of aminosilane gases include BTBAS (Bistertiarybutylaminosilane), BDMAS (Bisdimethylaminosilane), BDEAS (Bisdiethylaminosilane), DMAS (Dimethylaminosilane), DEAS (Diethylaminosilane), DPAS (Dipropylaminosilane), BAS (Butylaminosilane), BEMAS (Bisethylmethylaminosilane), TDMAS (Tridimethylaminosilane), HDMS (Hexamethyldisilazane), DMSDMA (Dimethylsilyldimethylamine), TMSDMA (Dimethilaminotrimethylsilane), TMMAS (Trimethylmethylaminosilane), TMICS (Trimethyl(isocyanato)silane), TMSA (Trimethylsilylacetylene), and TMSC (Trimethylsilylcyanide). Examples of silicon alkoxide gases include TEOS (Tetraethoxysilane). Furthermore, the silicon-containing gas may be 4DMAS (4-Dimethylaminosilane), DIPAS (Diisopropylaminosilane), or the like as the Si source gas.

[0084] Furthermore, while plasma CVD (Chemical Vapor Deposition) was used to form the first protective film in steps S1 and T1, the method for depositing the silicon-containing film is arbitrary. When forming the first protective film using an aminosilane-based gas, plasma CVD or ALD (Atomic Layer Deposition) may be used. In the case of plasma CVD, an oxygen-containing gas such as O2 gas is used as the additive gas. In the case of ALD, the steps of using an aminosilane-based gas and using an oxygen-containing gas plasma such as O2 gas are repeated. In the step using an aminosilane-based gas, an aminosilane-based gas plasma may be used, or a thermal adsorption reaction to the chamber internal components may be used without using plasma. Also, when forming the first protective film using a silicon alkoxide-based gas, plasma CVD may be used. In this case, an oxygen-containing gas such as O2 gas is used as the additive gas.

[0085] Furthermore, if the precursor gas of the first processing gas is a silicon-containing gas, in steps S3 and T5, the gas capable of removing the first protective film is a halogen-containing gas.

[0086] In the first and second embodiments described above, etching was performed as the plasma treatment, but the invention is not limited to this. For example, the technology of this disclosure can also be applied when a film deposition treatment is performed in steps S2 and T3.

[0087] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The above embodiments may be omitted, replaced, or modified in various ways without departing from the scope and spirit of the appended claims.

[0088] Furthermore, the following configuration examples also fall within the technical scope of this disclosure. (1)(a) A step of forming a first protective film on the surface of a component inside the chamber using a first treatment gas containing a halogen-free precursor gas, (b) A plasma treatment method comprising the step of plasma treatment of an object to be treated, which has been brought into the chamber, by plasma of a second treatment gas, after the first protective film has been formed on the surface of the member. (2)(c) The plasma treatment method according to (1), further comprising the step of removing the first protective film from the surface of the member by plasma of a third treatment gas containing a gas capable of removing the first protective film, after the plasma-treated member has been removed from the chamber. (3) The plasma treatment method according to (2), wherein the thickness of the first protective film formed in step (a) is greater than the depth to which the ions penetrate the first protective film when the ions generated by the plasma are irradiated onto the first protective film in step (c). (4) The precursor gas is a hydrocarbon gas, The plasma treatment method according to (2) or (3), wherein the gas capable of removing the first protective film is an oxygen-containing gas. (5) The precursor gas is a silicon-containing gas, The plasma treatment method according to (2) or (3), wherein the gas capable of removing the first protective film is a halogen-containing gas. (6)(d) The plasma treatment method according to any one of (1) to (5), further comprising the step of forming a second protective film on the first protective film by plasma of a fourth processing gas of the same type as the second processing gas, after step (a) and before step (b). (7) The plasma treatment method according to (6), wherein the process conditions in step (d) are the same as the initial process conditions in step (b). (8) A chamber for plasma processing of the object to be processed, A gas supply unit that supplies processing gas to the inside of the chamber, A plasma generation unit that generates plasma from the processing gas inside the chamber, It has a control unit and The control unit, (a) A step of forming a first protective film on the surface of a component inside the chamber using a first treatment gas containing a halogen-free precursor gas, (b) A plasma processing system that controls the gas supply unit and the plasma generation unit to perform the step of plasma processing an object to be processed, which has been brought into the chamber, with plasma from a second processing gas, after the first protective film has been formed on the surface of the member. (9) The plasma processing system according to (8), wherein the control unit controls the gas supply unit and the plasma generation unit to further perform the step of removing the first protective film from the surface of the member by plasma of a third processing gas containing a gas capable of removing the first protective film after the plasma-treated object to be processed has been transported out of the chamber. (10) The plasma processing system according to (9), wherein the control unit controls the gas supply unit and the plasma generation unit so that the thickness of the first protective film formed in step (a) is greater than the depth to which the ions generated by the plasma penetrate the first protective film when they are irradiated onto the first protective film in step (c). (11) The precursor gas is a hydrocarbon gas, The plasma processing system according to (9) or (10), wherein the gas capable of removing the first protective film is an oxygen-containing gas. (12) The precursor gas is a silicon-containing gas, The plasma treatment system according to (9) or (10), wherein the gas capable of removing the first protective film is a halogen-containing gas. (13) The plasma processing system according to any one of (8) to (12), wherein the control unit controls the gas supply unit and the plasma generation unit to further perform the step of forming a second protective film on the first protective film with a plasma of a fourth processing gas of the same type as the second processing gas, after the step of (a) and before the step of (b). (14) The plasma processing system according to (13), wherein the control unit controls the process conditions in step (d) to be the same as the initial process conditions in step (b). [Explanation of symbols]

[0089] 1. Plasma processing equipment 2 Control Unit 10 Plasma processing chamber 12 Plasma generation section 20 Gas Supply Department W board

Claims

1. (a) A step of forming a first protective film on the surface of a component inside the chamber using a first processing gas consisting only of CH4 gas, (b) After the first protective film is formed on the surface of the member, the process of plasma-treating the object to be processed, which has been brought into the chamber, with the plasma of the second processing gas, (c) After the plasma-treated object to be treated has been removed from the chamber, the first protective film is removed from the surface of the member by plasma of a third treatment gas containing a gas capable of removing the first protective film, A plasma treatment method wherein the thickness of the first protective film formed in step (a) is greater than the depth to which the ions penetrate the first protective film when the ions generated by the plasma are irradiated onto the first protective film in step (c).

2. The plasma treatment method according to claim 1, wherein the gas capable of removing the first protective film is an oxygen-containing gas.

3. (d) The plasma treatment method according to claim 1 or 2, further comprising the step of forming a second protective film on the first protective film by plasma of a fourth processing gas of the same type as the second processing gas, after step (a) and before step (b).

4. The plasma treatment method according to claim 3, wherein the process conditions in step (d) are the same as the first process conditions in step (b).

5. A chamber for plasma processing of the object to be processed, A gas supply unit that supplies processing gas to the inside of the chamber, A plasma generation unit that generates plasma from the processing gas inside the chamber, It has a control unit and The control unit, (a) A step of forming a first protective film on the surface of a component inside the chamber using a first processing gas consisting only of CH4 gas, (b) After the first protective film is formed on the surface of the member, the process of plasma-treating the object to be processed, which has been brought into the chamber, with the plasma of the second processing gas, (c) After the plasma-treated object to be processed has been removed from the chamber, the first protective film is removed from the surface of the member by plasma of a third processing gas containing a gas capable of removing the first protective film, A plasma processing system that controls the gas supply unit and the plasma generation unit such that the thickness of the first protective film formed in step (a) is greater than the depth to which the ions generated by the plasma penetrate the first protective film when they are irradiated onto the first protective film in step (c).

6. The plasma treatment system according to claim 5, wherein the gas capable of removing the first protective film is an oxygen-containing gas.

7. The plasma processing system according to claim 5 or 6, wherein the control unit controls the gas supply unit and the plasma generation unit to further perform the step of forming a second protective film on the first protective film with a plasma of a fourth processing gas of the same type as the second processing gas, after the step of (a) and before the step of (b).

8. The plasma processing system according to claim 7, wherein the control unit controls the process conditions in step (d) to be the same as the initial process conditions in step (b).

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