Substrate processing apparatus and substrate processing method

Abstract

To efficiently generate radicals while suppressing damage to a substrate.SOLUTION: A substrate processing apparatus according to one exemplary embodiment includes a processing container defining an internal space, a first gas supply configured to supply a first gas to a first space, a plasma generator configured to generate plasma of the first gas in the first space, a second gas supply configured to supply a second gas to a second space, a substrate support provided in a third space, and a mesh member disposed between the first space and the second space. And an energy supply unit that supplies energy to electrons in the second space by applying a pulse voltage between the mesh member and the collector plate, in which the pulse voltage periodically fluctuates between a first voltage level and a second voltage level, the first voltage level is a voltage level lower than the ionization voltage, and the second voltage level is a voltage level higher than the ionization voltage.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] SUMMARY OF THE DISCLOSURE Exemplary embodiments of the present disclosure relate to substrate processing apparatus and methods. [Background technology]

[0002] Highly active radicals are used in various substrate surface treatments such as film formation, cleaning, defect repair, and hydrophobic treatment of semiconductor substrates. For example, Patent Document 1 listed below describes a technology in which a catalyst is irradiated with an electron beam while a gas is being supplied to generate gaseous radicals, and the radicals are reacted with deposits to decompose and remove the deposits.

[0003] Patent Document 2 listed below describes a technique for depositing and growing silicon on a substrate by irradiating a gas containing hydrogen gas with an electron beam to generate gas plasma in a chamber, passing a silicon vapor flow through the plasma, and then supplying the silicon vapor flow to the substrate surface. In this technique, the silicon vapor flow is passed through the plasma, and silicon molecules or silicon clusters in the silicon vapor flow are reduced by hydrogen radicals in the plasma, thereby improving the quality of the silicon film deposited on the substrate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-151304 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-332497 Summary of the Invention [Problem to be solved by the invention]

[0005] When gas plasma is generated as in the technology described in Patent Document 2, positively charged ions are generated in the plasma. These ions are accelerated by the potential difference between the positively charged plasma and the substrate, and collide with the substrate. This can cause physical damage (ion irradiation damage) to the film-forming surface of the substrate, deteriorating the quality of the film on the substrate.

[0006] Therefore, there is a need for a substrate processing apparatus and a substrate processing method that can efficiently generate radicals while suppressing damage to the substrate. [Means for solving the problem]

[0007] A substrate processing apparatus according to one exemplary embodiment includes a processing vessel defining an internal space including a first space, a second space, and a third space; a first gas supply unit configured to supply a first gas to the first space; a plasma generation unit configured to generate plasma of the first gas in the first space; a second gas supply unit configured to supply a second gas to the second space; a substrate support provided in the third space; a mesh member disposed between the first space and the second space and having a plurality of through holes for selectively transmitting electrons in the plasma generated in the first space to the second space; and a plurality of electron beams disposed between the second space and the third space and communicating between the second space and the third space. and an energy supply unit that applies a pulse voltage between the mesh member and the collector plate to supply energy to electrons in the second space and irradiates the second gas with the energy-supplied electrons to generate radicals for substrate processing from the second gas, wherein the pulse voltage periodically fluctuates between a first voltage level and a second voltage level, and when a voltage level for increasing the kinetic energy of the electrons to an energy threshold for ionizing the second gas is defined as an ionization voltage, the first voltage level is a voltage level lower than the ionization voltage, and the second voltage level is a voltage level higher than the ionization voltage. [Effects of the Invention]

[0008] According to one exemplary embodiment, it is possible to efficiently generate radicals while suppressing damage to the substrate. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating a substrate processing apparatus according to an exemplary embodiment; [Figure 2] FIG. 2 is a schematic top view of an exemplary mesh member. [Figure 3] FIG. 2 is a schematic top view of an exemplary collector plate. [Figure 4] 10A and 10B are diagrams illustrating an example of the movement of charged particles within through-holes of a mesh member. [Figure 5] 1 is a diagram illustrating an example of the movement of charged particles in a plasma. [Figure 6] FIG. 1 is a diagram showing the reaction that occurs when electrons collide with hydrogen atoms (radicals) or hydrogen molecules, and the electron energy threshold at which the reaction occurs. [Figure 7] FIG. 4 is a diagram showing an example of a waveform of a pulse voltage. [Figure 8] FIG. 10 is a view schematically illustrating a substrate processing apparatus according to another embodiment. [Figure 9] 1 is a flowchart illustrating a substrate processing method according to an exemplary embodiment. [Figure 10] 1 is a diagram showing the plasma ignition process along with the potential distribution. DETAILED DESCRIPTION OF THE INVENTION

[0010] Various exemplary embodiments are described below.

[0011] A substrate processing apparatus according to one exemplary embodiment includes a processing vessel defining an internal space including a first space, a second space, and a third space; a first gas supply unit configured to supply a first gas to the first space; a plasma generation unit configured to generate plasma of the first gas in the first space; a second gas supply unit configured to supply a second gas to the second space; a substrate support provided in the third space; a mesh member disposed between the first space and the second space and having a plurality of through holes for selectively transmitting electrons in the plasma generated in the first space to the second space; and a plurality of electron beams disposed between the second space and the third space and communicating between the second space and the third space. and an energy supply unit that applies a pulse voltage between the mesh member and the collector plate to supply energy to electrons in the second space and irradiates the second gas with the energy-supplied electrons to generate radicals for substrate processing from the second gas, wherein the pulse voltage periodically fluctuates between a first voltage level and a second voltage level, and when a voltage level for increasing the kinetic energy of the electrons to an energy threshold for ionizing the second gas is defined as an ionization voltage, the first voltage level is a voltage level lower than the ionization voltage, and the second voltage level is a voltage level higher than the ionization voltage.

[0012] In the substrate processing apparatus according to the above embodiment, a pulse voltage that periodically changes between a first voltage level and a second voltage level is applied between the mesh member and the collector plate. When a voltage at the first voltage level that does not ionize the second gas is periodically applied to the mesh member, radicals can be selectively generated from the second gas without ionizing the second gas. This allows radical processing while suppressing ion irradiation damage to the substrate. However, it is known that the electron beam has a space charge limiting effect, and the maximum electron beam yield (electron density) is proportional to the 3 / 2 power of the voltage accelerating the electrons. In other words, to extract more electrons and generate more radicals, it is desirable to increase the voltage level. Furthermore, when an increased number of electrons are supplied from the plasma through the mesh member, the electrons tend to remain near the mesh member, which serves as a cathode, due to the space charge limiting effect, forming a so-called virtual cathode. On the other hand, when a second voltage level (a voltage level capable of ionizing the second gas) higher than the first voltage level is applied between the mesh member and the collector plate, the space charge limiting effect is alleviated compared to when the first voltage level is applied, the amount of electron beam that can be extracted increases, and electrons that have been retained in the virtual cathode can also reach the collector plate. As a result, the number of electrons irradiated to the second gas can be increased, and more radicals can be generated.

[0013] In one exemplary embodiment, the pulse voltage may have a pulse width (pulse voltage application time) and a duty ratio that prevent plasma of the second gas from being ignited in the second space. By preventing plasma of the second gas from being ignited, ion irradiation damage to the substrate can be more effectively suppressed.

[0014] In one exemplary embodiment, the plasma processing apparatus further includes a second mesh member separate from the first mesh member, the second mesh member being disposed between the first mesh member and the collector plate, and the energy supply unit may include a DC power supply that applies a DC voltage between the first mesh member and the second mesh member so that the potential of the first mesh member is lower than the potential of the second mesh member, and a variable DC power supply that applies a pulsed DC voltage between the second mesh member and the collector plate so that the potential of the second mesh member is lower than the potential of the collector plate. By providing the second mesh member between the first mesh member and the collector plate, ions in the plasma are prevented from leaking into the third space. Therefore, ion irradiation damage to the substrate can be more effectively suppressed.

[0015] In one exemplary embodiment, the aperture ratio of the first mesh member may be lower than the aperture ratio of the second mesh member. By making the aperture ratio of the first mesh member relatively small, the first mesh member can effectively block ions in the plasma.

[0016] In one exemplary embodiment, the collector plate may be electrically grounded.

[0017] In one exemplary embodiment, the first gas may include a noble gas.

[0018] In one exemplary embodiment, the second gas may include hydrogen gas.

[0019] In one exemplary embodiment, the first voltage level may be lower than the voltage level required to set the electron kinetic energy to 13.6 eV, and the second voltage level may be higher than the voltage level required to set the electron kinetic energy to 13.6 eV. The electron energy threshold for ionizing hydrogen radicals is 13.6 eV. By setting the first voltage level lower than the voltage level required to set the electron kinetic energy to 13.6 eV, the electron energy becomes lower than 13.6 eV. Therefore, generation of hydrogen ions during application of the voltage of the first power supply level can be suppressed. Furthermore, by setting the second voltage level higher than the voltage level required to set the electron kinetic energy to 13.6 eV, the current density between the mesh member and the collector plate can be increased, removing electrons accumulated in the virtual cathode and contributing to radical generation. Therefore, radicals can be generated efficiently.

[0020] In one exemplary embodiment, a substrate processing method is provided for processing a substrate in a process vessel defining an interior space including a first space, a second space, and a third space. This substrate processing method includes the steps of generating plasma of a first gas in a first space; applying a pulse voltage between a mesh member disposed between the first space and a second space and having a plurality of through holes for selectively transmitting electrons in the plasma generated in the first space into the second space, and a collector plate disposed between the second space and a third space and having a plurality of through holes communicating the second space with the third space, thereby supplying energy to the electrons that have passed through the mesh member; supplying a second gas to the second space and irradiating the second gas with the energized electrons to generate radicals from the second gas; and processing a substrate disposed in the third space using the radicals, wherein the pulse voltage periodically fluctuates between a first voltage level and a second voltage level, and when the voltage level for increasing the kinetic energy of the electrons to an energy threshold for ionizing the second gas is defined as an ionization voltage, the first voltage level is a voltage level lower than the ionization voltage, and the second voltage level is a voltage level higher than the ionization voltage.

[0021] As described above, according to the substrate processing method of the above embodiment, radicals can be efficiently generated while suppressing ion irradiation damage to the substrate.

[0022] In one exemplary embodiment, the pulse voltage may have a pulse width and a duty ratio that prevent plasma of the second gas from being ignited in the second space. By preventing plasma of the second gas from being ignited, ion irradiation damage to the substrate can be more effectively suppressed.

[0023] In one exemplary embodiment, the first gas may include a noble gas.

[0024] In one exemplary embodiment, the second gas may include hydrogen gas.

[0025] In one exemplary embodiment, the first voltage level may be lower than the voltage level for bringing the electron kinetic energy to 13.6 eV, and the second voltage level may be higher than the voltage level for bringing the electron kinetic energy to 13.6 eV.

[0026] Various exemplary embodiments will be described in detail below with reference to the drawings, in which the same or equivalent parts are designated by the same reference numerals.

[0027] Fig. 1 is a diagram schematically illustrating a substrate processing apparatus according to an exemplary embodiment. The substrate processing apparatus 1 illustrated in Fig. 1 is an inductively coupled substrate processing apparatus. The substrate processing apparatus 1 is an apparatus for generating radicals and processing a substrate using the radicals. In this specification, a radical refers to an electrically neutral, highly reactive atom or molecule that has an unpaired electron or an electron in an excited state.

[0028] As shown in FIG. 1, the substrate processing apparatus 1 includes a processing vessel 10, a plasma generating unit 11, a substrate support 12, a first gas supply unit 13, a second gas supply unit 14, a mesh member 15, a collector plate 16, and an energy supply unit 17.

[0029] The processing vessel 10 has a substantially cylindrical shape and defines an internal space 10s therein. The processing vessel 10 includes a dielectric window 101 and a sidewall 102. The sidewall 102 is made of, for example, aluminum. A plasma-resistant and radical-resistant film is formed on the inner surface of the sidewall 102. This film may be a film formed by anodizing or a ceramic film such as a film formed from yttrium oxide.

[0030] The processing vessel 10 includes an upper vessel portion 10A and a lower vessel portion 10B. The upper vessel portion 10A is supported on the lower vessel portion 10B via an insulating member 18. The insulating member 18 is provided on the lower vessel portion 10B and is made of an insulating material. The insulating member 18 is made of ceramic, such as quartz. That is, the upper vessel portion 10A and the lower vessel portion 10B are electrically insulated from each other. The upper vessel portion 10A defines a plasma generation space (first space) S1 for generating plasma therein.

[0031] The lower vessel part 10B is electrically grounded. The lower vessel part 10B defines therein an electron extraction space (second space) S2 and a processing space (third space) S3. That is, the internal space 10s includes the plasma generation space S1, the electron extraction space S2, and the processing space S3. The plasma generation space S1 is formed above the electron extraction space S2. The processing space S3 is formed below the electron extraction space S2. A passage 10p is formed in the sidewall of the lower vessel part 10B. The substrate W passes through the passage 10p when being transferred between the internal space 10s and the outside of the processing vessel 10. A gate valve 10g is provided along the sidewall of the lower vessel part 10B to open and close this passage 10p.

[0032] The plasma generation unit 11 includes an antenna 20. The antenna 20 is disposed on or above the processing vessel 10 (i.e., on or above the dielectric window 101). The antenna 20 includes one or more coils. In one embodiment, the antenna 20 may include an outer coil and an inner coil arranged coaxially. In this case, the power supply 30, which will be described later, may be connected to both the outer coil and the inner coil, or to either the outer coil or the inner coil.

[0033] The substrate processing apparatus 1 includes a gas introduction unit configured to introduce a first gas G1 into the internal space 10s. In one embodiment, the gas introduction unit includes a center gas injector (CGI) 21. The center gas injector 21 is attached to a central opening formed in the dielectric window 101. The center gas injector 21 has a gas supply port 21a, a gas flow path 21b, and a gas inlet port 21c. Note that the gas introduction unit may include one or more side gas injectors (SGI) attached to one or more openings formed in the sidewall 102 in addition to or instead of the center gas injector 21. The first gas supply unit 13 is connected to the gas supply port 21a.

[0034] The first gas supply unit 13 includes a valve 25, a flow rate controller 26, and a gas source 27. The valve 25 switches between supplying and stopping the supply of the first gas G1 to the gas supply port 21a. The flow rate controller 26 is a mass flow controller or a pressure-controlled flow rate controller. The gas source 27 is connected to the gas supply port 21a via the valve 25 and the flow rate controller 26. The gas source 27 supplies the first gas G1 to the gas supply port 21a via the valve 25 and the flow rate controller 26.

[0035] The first gas G1 is a gas for generating plasma. For example, the first gas G1 includes a rare gas such as helium gas (He), neon gas (Ne), argon gas (Ar), krypton gas (Kr), or xenon gas (Xe). The first gas G1 may be hydrogen gas or a mixed gas containing a rare gas and hydrogen gas. The first gas G1 supplied from the first gas supply unit 13 is supplied to the plasma generation space S1 via the gas supply port 21a, the gas flow path 21b, and the gas inlet port 21c. As described above, the first gas supply unit 13 can supply the first gas G1 to the plasma generation space S1 at a regulated flow rate.

[0036] The plasma generation unit 11 further includes a power supply 30. The power supply 30 is connected to the antenna 20 via a matching box 31 and generates power for plasma generation. The power supply 30 supplies high-frequency power having a frequency within a range of, for example, 10 MHz to 150 MHz to the antenna 20. In one embodiment, the power supply 30 may be configured to generate a plurality of source RF signals having different frequencies. The matching box 31 has a matching circuit for matching the output impedance of the power supply 30 with the impedance of the load side (antenna 20). The matching circuit of the matching box 31 may include a capacitor.

[0037] When power is supplied from the power source 30 to the antenna 20, the first gas G1 is excited in the plasma generation space S1, and plasma PL of the first gas G1 is generated. The plasma PL contains charged particles such as positive ions and electrons. For example, if the first gas G1 is argon gas, the plasma PL contains positive argon ions and negative electrons.

[0038] The substrate support 12 is provided in the processing space S3 and is configured to support the substrate W placed thereon. That is, the substrate W is disposed in the processing space S3. The substrate W has, for example, a substantially disk shape.

[0039] In one embodiment, the substrate support 12 includes a lower electrode 41 and an electrostatic chuck 42. The lower electrode 41 is made of a conductive material such as aluminum and has a substantially disk shape. A flow path 41f may be formed within the lower electrode 41. The flow path 41f is a flow path for a heat exchange medium. As the heat exchange medium, a liquid refrigerant or a refrigerant (e.g., chlorofluorocarbon) that cools the lower electrode 41 by vaporizing is used. A heat exchange medium circulation device (e.g., a chiller unit) is connected to the flow path 41f. This circulation device is installed outside the processing chamber 10. The heat exchange medium is supplied to the flow path 41f from the circulation device via piping (not shown). The heat exchange medium supplied to the flow path 41f is returned to the circulation device via piping (not shown). In another embodiment, the substrate support 12 may include a lower electrode and a heater.

[0040] In one embodiment, the substrate processing apparatus 1 may further include a power supply unit 45. The power supply unit 45 is configured to generate a DC voltage to be applied to the lower electrode 41. The power supply unit 45 is electrically connected to the lower electrode 41. In one embodiment, the power supply unit 45 supplies a negative DC voltage and a positive DC voltage to the lower electrode 41 via a low-pass filter 46.

[0041] The electrostatic chuck 42 is provided on the lower electrode 41. When the substrate W is processed in the processing space S3, it is placed on the electrostatic chuck 42 and held by the electrostatic chuck 42. The electrostatic chuck 42 has a body and an electrode. The body of the electrostatic chuck 42 is formed from a dielectric material such as aluminum oxide or aluminum nitride. The body of the electrostatic chuck 42 has a substantially disk shape. The electrostatic chuck 42 includes a substrate mounting region and a focus ring mounting region. The substrate mounting region is a region having a substantially disk shape. The upper surface of the substrate mounting region extends along a horizontal plane. An axis AX that includes the center of the substrate mounting region and extends vertically substantially coincides with the central axis of the processing vessel 10. When the substrate W is processed in the processing vessel 10, it is placed on the upper surface of the substrate mounting region.

[0042] The focus ring mounting region extends in the circumferential direction to surround the substrate mounting region. A focus ring FR is mounted on the upper surface of the focus ring mounting region. The focus ring FR has an annular shape. The substrate W is disposed within the region surrounded by the focus ring FR. That is, the focus ring FR surrounds the edge of the substrate W mounted on the substrate mounting region of the electrostatic chuck 42. The focus ring FR is made of, for example, silicon or silicon carbide.

[0043] The electrodes of the electrostatic chuck 42 are provided within the body of the electrostatic chuck 42. The electrodes of the electrostatic chuck 42 are films formed from a conductor. A DC power supply is electrically connected to the electrodes of the electrostatic chuck 42. When a DC voltage is applied from the DC power supply to the electrodes of the electrostatic chuck 42, an electrostatic attractive force is generated between the electrostatic chuck 42 and the substrate W. The generated electrostatic attractive force attracts the substrate W to the electrostatic chuck 42 and the substrate W is held by the electrostatic chuck 42.

[0044] An exhaust pipe 43 is connected to the bottom of the processing vessel 10 at a position between the substrate support 12 and the sidewall of the vessel lower part 10B. An exhaust device 44 is connected to the exhaust pipe 43. The exhaust device 44 has a pressure controller such as an automatic pressure control valve and a vacuum pump such as a turbomolecular pump, and can reduce the pressure in the internal space 10s.

[0045] The mesh member 15 is provided in the processing vessel 10 and is arranged between the plasma generation space S1 and the electron extraction space S2. That is, the mesh member 15 separates the plasma generation space S1 from the electron extraction space S2. The plasma generation space S1 is formed between the mesh member 15 and the dielectric window 101. The mesh member 15 is electrically connected to the vessel upper part 10A.

[0046] FIG. 2 is a top view schematically illustrating an exemplary mesh member 15. As shown in FIG. 2, the mesh member 15 includes an insulating plate 51 and multiple lattice portions 52. The insulating plate 51 is made of an insulator such as quartz and is formed in a substantially disk shape. The multiple lattice portions 52 are made of a conductive material and are arranged two-dimensionally within the insulating plate 51. Each of the multiple lattice portions 52 has multiple through-holes 15h that penetrate the mesh member 15 in the thickness direction. The multiple through-holes 15h communicate between the plasma generation space S1 and the electron extraction space S2. The multiple through-holes 15h have an opening width that blocks ions in the plasma PL generated in the plasma generation space S1 and allows electrons in the plasma PL to pass from the plasma generation space S1 to the electron extraction space S2.

[0047] The opening width of the plurality of through holes 15h refers to the width of the opening formed in the mesh member 15 by each of the through holes 15h. For example, if the planar shape of the through holes 15h is circular, the diameter of the through holes 15h is defined as the opening width of each of the through holes 15h. If the planar shape of the opening is a regular polygon, the diameter of a circle inscribed in the regular polygonal opening is defined as the opening width of each of the through holes 15h. The mesh member 15 shown in FIG. 2 has a plurality of through holes 15h, each of which has a substantially square planar shape.

[0048] The lattice portion 52 of the mesh member 15 is electrically connected to the container upper portion 10A via wiring WR. The lattice portion 52 of the mesh member 15 may be connected to the negative electrode of a variable DC power supply 50 (described later) via wiring WR. The wiring WR may be covered with an insulator such as quartz. The plurality of through holes 15h may be formed over substantially the entire surface of the mesh member 15.

[0049] The collector plate 16 is disposed between the electron extraction space S2 and the processing space S3. That is, the collector plate 16 is disposed between the substrate support 12 and the mesh member 15, and separates the electron extraction space S2 from the processing space S3. The electron extraction space S2 is formed between the mesh member 15 and the collector plate 16. The processing space S3 is formed between the bottom wall of the processing vessel 10 and the collector plate 16. Therefore, the substrate W is disposed in the processing space S3. The distance between the mesh member 15 and the collector plate 16 is, for example, 10 mm or less.

[0050] In one embodiment, the collector plate 16 is formed in a disk shape and is made of a metal such as stainless steel or aluminum. The surface of the collector plate 16 may be coated with a radical-resistant film or may be conductive. The collector plate 16 is supported by the lower vessel portion 10B and electrically connected to the lower vessel portion 10B. Therefore, the collector plate 16 is electrically grounded via the lower vessel portion 10B.

[0051] FIG. 3 is a top view schematically illustrating an exemplary collector plate 16. As shown in FIG. 3, the collector plate 16 has an outer peripheral portion 61 and a lattice portion 62. The outer peripheral portion 61 is formed in an annular shape. The lattice portion 62 has a mesh structure, a honeycomb structure, or a multi-hole structure and is connected to the inner peripheral edge of the outer peripheral portion 61. The lattice portion 62 of the collector plate 16 has a plurality of through holes 16h formed therein that penetrate the collector plate 16 in the thickness direction. The plurality of through holes 16h communicate between the electron extraction space S2 and the processing space S3. In one embodiment, the opening width of the plurality of through holes 15h in the mesh member 15 may be smaller than the opening width of the plurality of through holes 16h in the collector plate 16.

[0052] The opening width of the plurality of through holes 16h refers to the width of the opening formed by each through hole 16h in the collector plate 16. For example, when the planar shape of the through hole 16h is circular, the diameter of the circular opening is defined as the opening width of each through hole 16h, and when the planar shape of the opening is a regular polygon, the diameter of a circle inscribed in the regular polygonal opening is defined as the opening width of each through hole 16h.

[0053] In one embodiment, as shown in FIG. 3, a gas diffusion chamber 16a is formed inside the collector plate 16. The gas diffusion chamber 16a extends in an annular shape along the outer circumferential portion 61 of the collector plate 16. A lattice-shaped gas passage 16b is connected to the gas diffusion chamber 16a. The lattice-shaped gas passage 16b is formed inside a lattice portion 62. A plurality of gas discharge holes 16c are formed in the lattice portion 62, which communicate with the gas passage 16b and open toward the electron extracting space S2 (see FIG. 1). The plurality of gas discharge holes 16c extend obliquely upward (toward the mesh member 15) with respect to the axis AX. The plurality of gas discharge holes 16c communicate with the gas diffusion chamber 16a via the gas passage 16b.

[0054] A gas introduction port 63 is connected to the gas diffusion chamber 16a. A gas supply pipe 64 is connected to the gas introduction port 63. A second gas supply unit 14 is connected to the gas supply pipe 64. The second gas supply unit 14 includes a valve 65, a flow rate controller 66, and a gas source 67. The valve 65 has a function of switching between supplying and stopping gas to the gas supply pipe 64. The flow rate controller 66 is a mass flow controller or a pressure-controlled flow rate controller. The gas source 67 is connected to the gas supply pipe 64 via the valve 65 and the flow rate controller 66. The gas source 67 supplies the second gas G2 to the gas supply pipe 64 via the valve 65 and the flow rate controller 66.

[0055] The second gas G2 is a source gas for generating radicals for substrate processing. The second gas G2 is, for example, hydrogen gas (H2), nitrogen gas (N2), oxygen gas (O2), ammonia gas (NH3), or a mixture thereof. The second gas G2 supplied from the second gas supply unit 14 is supplied to the electron extracting space S2 via the gas supply pipe 64, the gas diffusion chamber 16a, the gas passage 16b, and the plurality of gas outlet holes 16c. As described above, the second gas supply unit 14 can supply the second gas G2 to the electron extracting space S2 at an adjusted flow rate.

[0056] In one embodiment, the substrate processing apparatus 1 may further include a controller MC. The controller MC is a computer including a processor, a storage device, an input device, a display device, etc., and controls each part of the substrate processing apparatus 1. Specifically, the controller MC executes a control program stored in the storage device and controls each part of the substrate processing apparatus 1 based on recipe data stored in the storage device. Under the control of the controller MC, a process specified by the recipe data is executed in the substrate processing apparatus 1. Substrate processing methods according to various embodiments can be executed in the substrate processing apparatus 1 under the control of each part of the substrate processing apparatus 1 by the controller MC.

[0057] The energy supply unit 17 includes a variable DC power supply 50 capable of generating DC pulses. The variable DC power supply 50 generates a pulse voltage for supplying energy to electrons that have passed through the multiple through-holes 15h of the mesh member 15. The anode of the variable DC power supply 50 is electrically grounded. The negative electrode of the variable DC power supply 50 is electrically connected to the mesh member 15 via the upper vessel portion 10A. Therefore, the mesh member 15 has a potential equal to that of the upper vessel portion 10A. The variable DC power supply 50 applies a pulsed DC voltage between the mesh member 15 and the collector plate 16 so that the potential of the mesh member 15 is lower than the potential of the collector plate 16. That is, a pulse voltage Vp of negative polarity relative to the potential of the collector plate 16 is applied to the mesh member 15. As a result, an electric field E is formed between the mesh member 15 and the collector plate 16, i.e., in the electron extraction space S2, from the collector plate 16 to the mesh member 15 (see FIG. 4).

[0058] The movement of charged particles in plasma PL will be described with reference to Figures 4 and 5. In Figures 4 and 5, a circle surrounding a "+", a circle surrounding a "-", a circle surrounding an "*", and a circle surrounding a "*" represent positive ions, electrons, and radicals, respectively.

[0059] As shown in Fig. 4, the plasma PL of the first gas G1 generated in the plasma generation space S1 contains positive ions and electrons. As described above, the mesh member 15 has a negative potential relative to the potential of the plasma PL, so an attractive force acts between the mesh member 15 and the positively charged positive ions. This attractive force causes the positive ions to be attracted to the mesh member 15 and collide with it, as shown in Fig. 4. More specifically, the positive ions are accelerated by the electric field of the sheath 70 formed between the plasma PL and the mesh member 15, collide with the mesh member 15, lose their charge, and return to an electrically neutral gas. Therefore, the mesh member 15 has the function of blocking the movement of positive ions in the plasma PL from the plasma generation space S1 to the electron extraction space S2.

[0060] On the other hand, a repulsive force acts between negatively charged electrons and the mesh member 15. Therefore, as shown in Fig. 4, the electrons in the plasma PL move from the plasma generation space S1 to the electron extraction space S2 through the multiple through-holes 15h without colliding with the mesh member 15. In other words, the mesh member 15 has the function of selectively transmitting electrons out of the positive ions and electrons in the plasma PL.

[0061] As shown in FIG. 5, electrons that pass through the multiple through-holes 15h of the mesh member 15 receive energy from the electric field E formed in the electron extraction space S2 and are accelerated. As a result, an electron beam 60 is formed in the electron extraction space S2. The electron beam 60 is irradiated onto the second gas G2 supplied to the electron extraction space S2 through the multiple gas outlet holes 16c. As a result, the electrons constituting the electron beam 60 collide with molecules of the second gas G2, dissociating the molecules and generating radicals. The substrate W placed in the processing space S3 is processed by the radicals generated in the electron extraction space S2. Meanwhile, the electrons constituting the electron beam 60 are attracted to and collected by the collector plate 16, which has a relatively high potential.

[0062] Here, when the electron beam 60 is irradiated onto the second gas G2, the reaction that occurs in the molecules or atoms of the second gas G2 varies depending on the kinetic energy of the electrons constituting the electron beam 60. For example, when the electron beam 60 containing electrons with excessive kinetic energy is irradiated onto the second gas G2, plasma of the second gas G2 is generated in the electron extraction space S2. The plasma generated in the electron extraction space S2 easily diffuses into the processing space S3. Ions in this plasma are accelerated by the potential difference between the ions and the substrate W and collide with the substrate W. The ion collisions cause physical damage (ion irradiation damage) to the surface of the substrate W.

[0063] Figure 6 shows the reactions that occur when electrons collide with hydrogen molecules or hydrogen atoms (radicals), as well as the electron energy threshold at which these reactions occur. As shown in Figure 6, when hydrogen molecules are irradiated with electrons having an energy of 8.8 eV or more, the hydrogen molecules dissociate and hydrogen radicals are generated. Hydrogen radicals are electrically neutral hydrogen atoms with one unpaired electron. On the other hand, when hydrogen radicals are irradiated with electrons having an energy of 13.6 eV or more, the hydrogen radicals are ionized and hydrogen ions are generated.

[0064] When hydrogen ions are formed in the electron extraction space S2, the hydrogen ions are accelerated by the potential difference between the plasma PL and the substrate W and collide with the substrate W. As a result, physical damage may occur to the substrate W. Therefore, in order to suppress such damage, the energy supply unit 17 supplies a pulse voltage Vp to the mesh member 15 so as to prevent plasma from being ignited in the electron extraction space S2.

[0065] FIG. 7 shows an example of the waveform of the pulse voltage Vp applied between the mesh member 15 and the collector plate 16 from the variable DC power supply 50. The waveform shown in FIG. 7 shows the change in the potential of the collector plate 16 when the potential of the mesh member 15 is used as a reference. As shown in FIG. 7, the voltage level (potential) of the pulse voltage Vp periodically changes between a first voltage level V1 and a second voltage level V2. The absolute value of the first voltage level V1 is higher than the radicalization voltage Vrad and lower than the ionization voltage Vion. The absolute value of the first voltage level V1 is lower than the ionization voltage Vion. The absolute value of the second voltage level V2 is higher than the ionization voltage Vion.

[0066] The ionization voltage Vion is a voltage for accelerating electrons so that the energy of the electrons in the electron extraction space S2 reaches the minimum energy (hereinafter referred to as the "ionization energy threshold") that can ionize the second gas G2 through collision. As described above, the ionization energy threshold of hydrogen radicals is 13.6 eV. That is, if the second gas G2 is hydrogen gas and the energy (initial energy) of the electrons immediately after moving to the electron extraction space S2 is assumed to be approximately zero, the ionization voltage Vion is 13.6 eV. Therefore, when the second gas G2 is hydrogen gas, the second voltage level V2 can be set to, for example, a voltage higher than 13.6 V.

[0067] The radicalization voltage Vrad is a voltage for accelerating electrons so that the energy of the electrons in the electron extraction space S2 reaches the minimum energy (hereinafter referred to as the "radicalization energy threshold") that can radicalize the second gas G2 through collision. As described above, the radicalization energy threshold for hydrogen molecules is 8.8 eV. That is, if the second gas G2 is hydrogen gas and the energy (initial energy) of the electrons immediately after moving to the electron extraction space S2 is assumed to be approximately zero, the radicalization voltage Vrad is 8.8 V. In this case, the first voltage level V1 can be set to, for example, a voltage higher than 8.8 V and lower than 13.6 V.

[0068] As described above, when a voltage higher than the ionization voltage Vion is applied between the mesh member 15 and the collector plate 16, the electron energy becomes higher than 13.6 eV, and hydrogen ions are generated in the electron extraction space S2. On the other hand, when a voltage higher than the radicalization voltage Vrad but lower than the ionization voltage Vion is applied between the mesh member 15 and the collector plate 16, hydrogen ions are not generated, and hydrogen radicals are generated in the electron extraction space S2.

[0069] During the period τ1 during which the first voltage level V1 is applied, energy is supplied to electrons so that their energy is higher than the radicalization energy threshold but lower than the ionization energy threshold, thereby suppressing the generation of ions in the second gas G2. Meanwhile, during the period τ2 during which the second voltage level V2 is applied, ions are temporarily generated from the second gas G2. However, by setting the period τ2 to be shorter than the time it takes for plasma to ignite and returning the applied voltage to the first voltage level V1, the generation of plasma in the electron extraction space S2 is suppressed. Furthermore, during the period τ2, the strength of the electric field E generated in the electron extraction space S2 increases, allowing electrons accumulated in the virtual cathode to reach the collector plate 16. That is, the current density between the mesh member 15 and the collector plate 16 increases, increasing the amount of radicals generated. Therefore, by applying a pulse voltage Vp that periodically fluctuates between the first voltage level V1 and the second voltage level V2 to the mesh member 15, radicals can be efficiently generated while suppressing ion irradiation damage to the substrate W.

[0070] As described above, during period τ2, the electron energy becomes higher than the ionization energy threshold. Therefore, if period τ2 is longer than the time required for plasma ignition, or if period τ1 is shorter than the time required for remaining ions to reach the mesh, plasma is generated in electron extraction space S2. That is, if the duty ratio (=τ2 / (τ1+τ2)×100[%]), which is the ratio of the time length of the second voltage level V2 to the cycle of pulse voltage Vp, becomes high, plasma is generated in electron extraction space S2. In this case, there is a risk of significant damage to the substrate W. Therefore, the pulse voltage Vp is set to a pulse width and duty ratio that do not ignite plasma of the second gas G2.

[0071] To efficiently generate radicals, it is necessary to increase the density of the electron beam 60 irradiated into the second gas G2 (the current density between the mesh member 15 and the collector plate 16). However, when the voltage level of the pulse voltage Vp is low or when a large number of electrons are extracted from the mesh member 15, a group of electrons may gather near the mesh member 15, forming a negative potential in the electron extraction space S2. This negative potential is called a potential valley or a virtual cathode. Due to the effect of this virtual cathode, even if the number of electrons extracted from the mesh member 15 is increased, there is a limit to the increase in the current density between the mesh member 15 and the collector plate 16.

[0072] Here, when a voltage is applied between the cathode and anode to generate an electron beam, the current density J that flows between the cathode and anode is expressed by the following formula (1) (Child-Langmuir law). At this time, the voltage distribution between the cathode and anode is expressed by the following formula (2).

[0073]

number

[0074]

number

[0075] In equation (1), ε0 is the permittivity of vacuum, m is the electron mass, V0 is the voltage between the cathode and anode, and d is the distance between the cathode and anode. In equation (2), z is the distance from the cathode.

[0076] As shown in equation (1), the current density J between the cathode and anode is proportional to the 3 / 2 power of the voltage V0 applied between the cathode and anode and inversely proportional to the square of the distance d between the cathode and anode. Furthermore, as shown in equation (2), the voltage in the space between the cathode and anode is proportional to the 4 / 3 power of the distance z from the cathode. In other words, the density of the electron beam formed between the cathode and anode increases as the voltage applied between the cathode and anode increases or the distance between the cathode and anode decreases. When the voltage V0 is relatively small or when excessive electron emission results in the formation of a virtual cathode, a potential valley forms at the virtual cathode, where electrons accumulate, as shown in state A1 in Figure 10. The potential distribution from this potential valley to the anode (collector plate 16 in Figure 10) is proportional to the 3 / 2 power of the voltage V0 due to the space charge limiting effect.

[0077] As described above, in the substrate processing apparatus 1 according to the embodiment, a pulse voltage Vp, which periodically varies between a first voltage level V1 and a second voltage level V2, is applied between the mesh member 15 and the collector plate 16. When the first voltage level V1, which does not ionize the second gas G2, is periodically applied to the mesh member 15, radicals can be selectively generated from the second gas G2 without ionizing the second gas G2. Therefore, radical processing can be performed while suppressing ion irradiation damage to the substrate W. However, it is known that the space charge limiting effect exists in the electron beam, and the maximum electron beam quantity (electron density) that can be extracted is proportional to the 3 / 2 power of the voltage accelerating the electrons. In other words, to extract more electrons and generate more radicals, it is desirable to increase the voltage level. Furthermore, when an increased number of electrons are supplied from the plasma via the mesh, the electrons tend to remain near the cathode (in this case, the mesh member) due to the space charge limiting effect, forming a so-called virtual cathode. On the other hand, when a voltage of a second voltage level V2 (a voltage level capable of ionizing the second gas G2) higher than the first voltage level V1 is applied between the mesh member 15 and the collector plate 16, the space charge limiting effect is alleviated compared to when the first voltage level V1 is applied, the amount of electron beam that can be extracted increases, and electrons that have been retained in the virtual cathode can also reach the collector plate 16. As a result, the number of electrons irradiated to the second gas G2 can be increased, and more radicals can be generated.

[0078] However, if the second voltage level V2 is continued to be applied, the second gas G2 will be ionized, leading to the ignition of plasma. Once the plasma is ignited, the plasma will easily diffuse to the substrate W, causing physical damage (ion irradiation damage) to the film formation surface of the substrate W. Therefore, by applying the voltage of the second voltage level V2 in pulse form with a time width shorter than the time it takes for the plasma to ignite during the application period τ2, and appropriately adjusting the pulse width and duty ratio, it becomes possible to efficiently generate radicals while suppressing the ignition (generation) of plasma.

[0079] Here, referring to FIG. 10, we will explain how plasma is generated when a voltage of the second voltage level V2 is steadily applied. FIG. 10 shows the distribution of potential (voltage) relative to the position from the mesh member 15 to the collector plate 16. In state A1, a voltage of the first voltage level V1 is steadily applied. Due to the space charge limiting effect, a virtual cathode is formed near the mesh member 15, and electrons accumulate there. When the applied voltage is then increased stepwise to the second voltage level V2, the electric field becomes stronger, and the electrons accumulated at the virtual cathode are first accelerated toward the collector plate 16, and the potential valley begins to shallow (state A2). At this time, the accelerated electrons contribute to the generation of radicals by colliding with the second gas G2. At the same time, some of the electrons ionize the second gas G2. However, the (still remaining) potential valley acts as a barrier, preventing efficient supply of electrons from the mesh member 15, preventing plasma ignition. As time passes, the electrons that had accumulated in the virtual cathode disappear from the collector plate 16, and the potential valley also disappears (state A3). Then, the supply of electrons from the cathode becomes active, and since ionization has already begun, the space approaches electrical neutrality, the space charge restriction disappears, an electron avalanche occurs, and the plasma ignites (state A4). When plasma ignition is complete, the gas becomes more conductive, the potential in the plasma becomes flat, and a sheath is formed mainly on the mesh member 15 side (cathode side). When this state is reached, it can be defined that the plasma has ignited. When the space is filled with electrons only and space charge restriction is applied, the electron density is approximately 10 8 cm -3 The ion density is approximately 10 6 cm -3 When the plasma is ignited, the electron density and ion density both reach approximately 10 8 cm -3 That's all.

[0080] If the second voltage level V2 is applied in a pulsed manner and the applied voltage is returned to the first voltage level V1 before plasma ignition, the ions generated during application of the second voltage level V2 reach the mesh member 15 due to the potential difference and disappear, preventing plasma ignition. Furthermore, because the electric field between the mesh member 15 and the collector plate 16 weakens, a virtual cathode is again formed near the mesh member 15, and electrons accumulate there. After the ions generated during application of the second voltage level V2 disappear, applying the second voltage level V2 again as a pulse shorter than the time required for plasma ignition accelerates the electrons accumulated at the virtual cathode toward the collector plate 16, contributing to the generation of radicals. In this way, by alternately applying the first voltage level V1 and the second voltage level V2—that is, by steadily applying the first voltage level V1 and repeatedly applying a pulsed DC voltage at the second voltage level V2—the substrate processing apparatus 1 can efficiently generate radicals while suppressing substrate damage.

[0081] The pulse width and duty ratio of the pulse voltage Vp that prevent plasma of the second gas G2 from igniting will be described below. As described above, when a voltage of the second voltage level V2 is applied to the mesh member 15, ions of the second gas G2 are generated in the electron extraction space S2. However, there is a time lag between the application of the voltage of the second voltage level V2 and the ignition of plasma of the second gas G2. The time until plasma ignition can be considered to be the time until electrons constituting the virtual cathode reach the collector plate 16 and the potential valley disappears. Hereinafter, this time will be referred to as τp0. Even when a voltage of the second voltage level V2 is applied, only a small amount of ionization occurs before plasma ignition, so the Child-Langmuir law described above applies. That is, electrons reach the collector plate 16 at a rate determined by the space charge limiting current Jp (Equation (3) below) determined by the second voltage level V2. Therefore, the time until plasma ignition τp0 is expressed by Equation (4) below.

[0082]

number

[0083]

number

[0084] In equation (4), N is the surface density of electrons accumulated on the virtual cathode as seen from the direction of electron beam travel (the width of the virtual cathode along the direction of electron beam travel × electron density [m -2 ]).

[0085] Next, consider how long it takes for ions generated when the applied voltage is changed from the second voltage level V2 to the first voltage level V1 to disappear. While the first voltage level V1 is being applied, ions generated when the immediately preceding second voltage level V2 was applied and present in the electron extraction space S2 are accelerated by the electric field, reach the first mesh, and disappear. The time τe0 for ions located at the farthest position from the first mesh, i.e., near the substrate W, to reach the first mesh is expressed by the following equation (5):

[0086]

number

[0087] In equation (5), M is the mass of the ion, and the electric field is derived by approximating it as constant at V1 / d regardless of location. That is, to prevent plasma ignition, it is required that the period τ2 during which the voltage of the second voltage level V2 is applied is equal to or shorter than τp0, and that the period τ1 during which the voltage of the first voltage level V1 is applied is equal to or longer than τe0. The duty ratio in this case is expressed by equation (6) below. That is, if τ2 is set to be equal to or shorter than τp0 and the duty ratio of the pulse voltage Vp is set to be equal to or shorter than the duty ratio D [%] shown in equation (6), plasma ignition can be avoided.

[0088]

number

[0089] This condition is equivalent to making τ1 equal to or greater than τe0 and making the duty ratio equal to or less than D.

[0090] Next, a substrate processing apparatus according to another embodiment will be described. Fig. 8 is a cross-sectional view schematically showing a substrate processing apparatus 1A according to another embodiment. In the following description, differences from the substrate processing apparatus 1 shown in Fig. 1 will be mainly described, and overlapping descriptions will be omitted.

[0091] As shown in FIG. 8, the substrate processing apparatus 1A includes a first mesh member 15A and a second mesh member 15B. The first mesh member 15A has the same configuration as the mesh member 15 described above. The second mesh member 15B is disposed between the first mesh member 15A and the collector plate 16. The second mesh member 15B has a plurality of through holes 115h formed therein, penetrating the second mesh member 15B in the thickness direction. In one embodiment, the opening width of the plurality of through holes 15h in the first mesh member 15A may be smaller than the opening width of the plurality of through holes 115h in the second mesh member 15B. The second mesh member 15B is electrically insulated from the first mesh member 15A by an insulating member 18A interposed between the first mesh member 15A and the second mesh member 15B. The second mesh member 15B is also electrically insulated from the collector plate 16 by an insulating member 18B interposed between the second mesh member 15B and the collector plate 16.

[0092] The aperture ratio of the first mesh member 15A may be lower than the aperture ratio of the second mesh member 15B. The aperture ratio of the first mesh member 15A refers to the ratio of the total area of ​​the plurality of through holes 15h seen from the thickness direction to the area of ​​the first mesh member 15A seen from the thickness direction. For example, the aperture ratio of the first mesh member 15A is 10% or less. Similarly, the aperture ratio of the second mesh member 15B refers to the ratio of the total area of ​​the plurality of through holes 115h seen from the thickness direction to the area of ​​the second mesh member 15B seen from the thickness direction. For example, the aperture ratio of the second mesh member 15B is 10% or more and 50% or less.

[0093] The energy supply unit 17 of the substrate processing apparatus 1A further includes a variable DC power supply 50 and a DC power supply 81. The anode of the variable DC power supply 50 is electrically grounded. The negative electrode of the variable DC power supply 50 is electrically connected to the second mesh member 15B. The variable DC power supply 50 applies a pulsed DC voltage Vd between the second mesh member 15B and the collector plate 16 so that the potential of the second mesh member 15B is lower than the potential of the collector plate 16. In other words, a pulsed voltage of negative polarity is applied to the second mesh member 15B with respect to the potential of the collector plate 16.

[0094] The positive electrode of the DC power supply 81 is electrically connected to the second mesh member 15B. The negative electrode of the DC power supply 81 is electrically connected to the first mesh member 15A. The DC power supply 81 applies a voltage Vc between the first mesh member 15A and the second mesh member 15B so that the potential of the first mesh member 15A is lower than the potential of the second mesh member 15B. In other words, a voltage of negative polarity is applied to the first mesh member 15A with respect to the potential of the second mesh member 15B. Therefore, the potentials of the first mesh member 15A, the second mesh member 15B, and the collector plate 16 increase in this order.

[0095] The composite voltage of the pulsed DC voltage Vd and the voltage Vc may be the same as the pulse voltage Vp shown in Fig. 7. That is, the voltage Vc is lower than the ionization voltage Vion. By applying this composite voltage between the first mesh member 15A and the collector plate 16, radicals for substrate processing can be efficiently generated while suppressing damage to the substrate W.

[0096] Furthermore, in the substrate processing apparatus 1A, the ions in the plasma PL generated in the plasma generation space S1 are blocked by the first mesh member 15A and the second mesh member 15B, so that the ions in the plasma PL can be effectively prevented from leaking into the processing space S3, thereby further suppressing ion irradiation damage to the substrate.

[0097] A substrate processing method according to one exemplary embodiment will be described below with reference to Fig. 9. Fig. 9 is a flowchart showing a substrate processing method according to one exemplary embodiment. The substrate processing method shown in Fig. 9 (hereinafter referred to as "method MT") is performed using the substrate processing apparatus 1 or substrate processing apparatus 1A described above.

[0098] 9, in the method MT, first, a substrate W is placed on a substrate support 12 (step ST1). Next, a first gas G1 is supplied from a first gas supply unit 13 to a plasma generation space S1 (step ST2). The first gas G1 is, for example, a rare gas such as argon gas (Ar). The first gas G1 may be continuously supplied to the plasma generation space S1 during the execution of the method MT.

[0099] Next, power is supplied from the power source 30 to the antenna 20, and a plasma PL of the first gas G1 is generated in the plasma generation space S1 (step ST3). Power may be continuously supplied from the power source 30 to the antenna 20 during the execution of the method MT.

[0100] Next, in order to extract electrons in the plasma PL from the plasma generation space S1 to the electron extraction space S2, the variable DC power supply 50 of the energy supply unit 17 applies a pulse voltage Vp between the mesh member 15 and the collector plate 16 so that the potential of the mesh member 15 is lower than the potential of the collector plate 16 (step ST4). At this time, as shown in FIG. 7, the applied pulse voltage Vp has a waveform that periodically changes between a first voltage level V1 lower than the ionization voltage Vion and a second voltage level V2 higher than the ionization voltage Vion. By applying the pulse voltage Vp between the mesh member 15 and the collector plate 16, electrons in the plasma PL are attracted to the collector plate 16, which has a relatively high potential, and move to the electron extraction space S2. That is, electrons in the plasma PL are selectively extracted to the electron extraction space S2.

[0101] As shown in FIG. 8, when a second mesh member 15B is provided between the first mesh member 15A and the collector plate 16, a pulsed DC voltage may be applied between the second mesh member 15B and the collector plate 16 so that the potential of the second mesh member 15B is lower than the potential of the collector plate 16, and a DC voltage may be applied between the first mesh member 15A and the second mesh member 15B so that the potential of the first mesh member 15A is lower than the potential of the second mesh member 15B.

[0102] Next, the second gas G2 is supplied from the second gas supply unit 14 to the electron extraction space S2 (step ST5). The second gas G2 is, for example, hydrogen gas. The second gas G2 supplied to the electron extraction space S2 is irradiated with the electrons extracted to the electron extraction space S2. As a result, radicals are generated from the second gas G2 due to collision of the electrons. Here, since the first voltage level V1 has a voltage higher than the radicalization voltage Vrad and lower than the ionization voltage Vion, during the period τ1 during which the first voltage level V1 is applied, the electrons are supplied with energy higher than the radicalization energy threshold but lower than the ionization energy threshold. For example, when the second gas G2 is hydrogen gas, the electric field E generated by the application of the first voltage level V1 causes the energy of the electrons in the electron extraction space S2 to be 8.8 eV or more and 13.6 eV or less. When the electron beam 60 of electrons having such energy collides with the hydrogen gas, the generation of hydrogen ions is suppressed and hydrogen radicals are selectively generated. Furthermore, during the period τ1, due to the constraints of the current density, a group of electrons gathers near the mesh member 15, forming a virtual cathode in the electron extraction space S2.

[0103] On the other hand, since the second voltage level V2 is higher than the ionization voltage Vion, during the period τ2 during which the second voltage level V2 is applied, electrons are supplied with energy higher than the ionization energy threshold. For example, when the second gas G2 is hydrogen gas, the energy of the electrons in the electron extraction space S2 is 13.6 eV or higher. When the electron beam 60 of electrons having such energy collides with the hydrogen gas, ions are temporarily generated from the second gas G2. However, because the pulse voltage Vp has a pulse width and duty ratio that do not ignite plasma of the second gas G2, the generated ions eventually disappear, and the generation of plasma in the electron extraction space S2 is suppressed.

[0104] During period τ2, the strength of the electric field E generated in the electron extraction space S2 increases, and the current density (electron density and electron movement speed) between the mesh member 15 and the collector plate 16 increases. Furthermore, by increasing the strength of the electric field E, the virtual cathode formed near the mesh member 15 during period τ1 can be removed. This makes it possible to extract electrons into the electron extraction space S2 with high efficiency, and to generate radicals efficiently.

[0105] Next, the substrate W placed in the processing space S3 is exposed to the radicals and processed (step ST6). At this time, since the generation of plasma of the second gas G2 is suppressed in the processing space S3, physical damage to the substrate W due to ions can be suppressed.

[0106] In one embodiment, the first voltage level V1 of the pulse voltage Vp may be a voltage that supplies energy to electrons so that the kinetic energy of the electrons is higher than the threshold energy required to excite ground-state radicals generated from the second gas G2. For example, as shown in FIG. 6, when electron energy of 10.2 eV or more is supplied to hydrogen atoms (hydrogen radicals), the hydrogen radicals transition from the ground state to an excited state. Therefore, when the initial energy of the electrons is approximately zero and the second gas G2 is hydrogen gas, the first voltage level V1 is set to 10.2 V or more and 13.6 V or less. By setting the first voltage level V1 to 10.2 V or more and 13.6 V or less, the electron energy becomes 10.2 eV or more and 13.6 eV or less. By irradiating the second gas G2 with the electron beam 60 of electrons having such energy, the hydrogen radicals transition from the ground state to an excited state, generating highly reactive excited-state hydrogen radicals. By using these excited-state hydrogen radicals, the substrate W can be processed more efficiently.

[0107] As described above, in the method MT, energy is supplied to electrons that have moved from the plasma generation space S1 to the electron extraction space S2 to generate the electron beam 60, and the second gas G2 is irradiated with the electron beam 60. Here, in the method MT, a pulse voltage Vp that periodically changes between the first voltage level V1 and the second voltage level V2 is applied to the mesh member 15, so that radicals can be efficiently generated while suppressing ion irradiation damage to the substrate W. Therefore, according to the method MT, the substrate can be efficiently processed using radicals while suppressing physical damage to the substrate W caused by ions.

[0108] Although various exemplary embodiments have been described above, the present invention is not limited to the above-described exemplary embodiments, and various omissions, substitutions, and modifications may be made. Furthermore, elements in different embodiments may be combined to form other embodiments.

[0109] For example, although the substrate processing apparatus 1 is an inductively coupled plasma processing apparatus, the substrate processing apparatus 1 according to another embodiment may be a plasma processing apparatus of another type. Furthermore, the method MT may be performed using any type of plasma processing apparatus other than the substrate processing apparatus 1. For example, the plasma generated in the plasma generation space S1 by the plasma generation unit 11 may be capacitively coupled plasma (CCP), inductively coupled plasma (ICP), electron-cyclotron-resonance plasma (ECR plasma), helicon wave plasma (HWP), or surface wave plasma (SWP). Various types of plasma generation units 11, including alternating current (AC) plasma generation units and direct current (DC) plasma generation units, may be used. Plasma excitation methods based on electrodeless discharge, such as inductively coupled plasma and surface wave plasma, in which no electrodes are inserted into the plasma, allow for the electrical circuitry to be configured independently of the electrical circuitry of the energy supply unit, improving the flexibility of the device configuration.

[0110] 1 and 8, the second gas G2 is supplied to the electron extracting space S2 from a plurality of gas discharge holes 16c formed in the collector plate 16, but the supply path of the second gas G2 does not necessarily have to be formed in the collector plate 16. For example, the supply path of the second gas G2 may be formed in the mesh member 15, or the second gas G2 may be supplied through the side wall of the container lower part 10B.

[0111] The steps of method MT may be performed simultaneously or in any order, unless inconsistent. The methods described in this disclosure present various steps using an exemplary order and are not limited to the particular order presented.

[0112] From the foregoing, it will be understood that various embodiments of the present disclosure have been described herein for purposes of illustration, and that various modifications may be made without departing from the scope and spirit of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the appended claims.

[0113] [1] A processing vessel defining an interior space including a first space, a second space, and a third space; a first gas supply unit configured to supply a first gas to the first space; a plasma generating unit configured to generate plasma of the first gas in the first space; a second gas supply unit configured to supply a second gas to the second space; a substrate support provided in the third space; a mesh member disposed between the first space and the second space, the mesh member having a plurality of through holes for selectively transmitting electrons in the plasma generated in the first space to the second space; a collector plate disposed between the second space and the third space and having a plurality of through holes communicating the second space with the third space; an energy supply unit that applies a pulse voltage between the mesh member and the collector plate to supply energy to the electrons in the second space and irradiates the second gas with the electrons to which energy has been supplied, thereby generating radicals for substrate processing from the second gas; Equipped with The pulse voltage periodically varies between a first voltage level and a second voltage level, and when a voltage level for increasing the kinetic energy of the electrons to an energy threshold for ionizing the second gas is defined as an ionization voltage, the first voltage level is a voltage level lower than the ionization voltage, and the second voltage level is a voltage level higher than the ionization voltage. Substrate processing equipment.

[0114] [2] The substrate processing apparatus according to claim 1, wherein the pulse voltage has a pulse width and a duty ratio that do not ignite plasma of the second gas in the second space.

[0115] [3] The device further includes a second mesh member separate from the first mesh member, the second mesh member is disposed between the first mesh member and the collector plate; The energy supply unit is a DC power supply that applies a DC voltage between the first mesh member and the second mesh member so that the potential of the first mesh member is lower than the potential of the second mesh member; a variable DC power supply that applies a pulsed DC voltage between the second mesh member and the collector plate so that the potential of the second mesh member is lower than the potential of the collector plate; The substrate processing apparatus according to [1] or [2], comprising:

[0116] [4] The substrate processing apparatus according to [3], wherein the opening ratio of the first mesh member is lower than the opening ratio of the second mesh member.

[0117] [5] The substrate processing apparatus according to any one of [1] to [4], wherein the collector plate is electrically grounded.

[0118] [6] The substrate processing apparatus according to any one of [1] to [5], wherein the first gas contains a rare gas.

[0119] [7] The substrate processing apparatus according to any one of [1] to [6], wherein the second gas contains hydrogen gas.

[0120] [8] The substrate processing apparatus described in [7], wherein the first voltage level is lower than the voltage level for setting the kinetic energy of the electrons to 13.6 eV, and the second voltage level is higher than the voltage level for setting the kinetic energy of the electrons to 13.6 eV.

[0121] [9] A substrate processing method for processing a substrate in a processing vessel defining an internal space including a first space, a second space, and a third space, comprising: generating plasma of a first gas in the first space; a step of applying a pulse voltage between a mesh member disposed between the first space and the second space and having a plurality of through holes for selectively transmitting electrons in the plasma generated in the first space to the second space, and a collector plate disposed between the second space and the third space and having a plurality of through holes communicating the second space with the third space, thereby supplying energy to the electrons that have transmitted through the mesh member; supplying a second gas into the second space and irradiating the second gas with the electrons to which energy has been supplied to generate radicals from the second gas; treating the substrate placed in the third space with the radicals; Including, the pulse voltage periodically fluctuates between a first voltage level and a second voltage level, and when a voltage level for increasing the kinetic energy of the electrons to an energy threshold for ionizing the second gas is defined as an ionization voltage, the first voltage level is a voltage level lower than the ionization voltage, and the second voltage level is a voltage level higher than the ionization voltage. Substrate processing method.

[0122]

[10] The substrate processing method according to [9], wherein the pulse voltage has a duty ratio such that plasma of the second gas is not ignited in the second space.

[0123]

[11] The substrate processing method according to claim [9] or

[10] , wherein the first gas includes a rare gas.

[0124]

[12] The substrate processing method according to any one of [9] to

[11] , wherein the second gas contains hydrogen gas.

[0125]

[13] A substrate processing method according to

[12] , wherein the first voltage level is lower than the voltage level for setting the kinetic energy of the electrons to 13.6 eV, and the second voltage level is higher than the voltage level for setting the kinetic energy of the electrons to 13.6 eV. [Explanation of symbols]

[0126] 1, 1A...substrate processing apparatus, 10...processing vessel, 10s...internal space, 11...plasma generation section, 12...substrate support, 13...first gas supply section, 14...second gas supply section, 15...mesh member, 15A...first mesh member, 15B...second mesh member, 15h, 16h, 115h...through holes, 16...collector plate, 17...energy supply section, 50...variable DC power supply, 81...DC power supply, D...duty ratio, G1...first gas, G2...second gas, PL...plasma, S1...plasma generation space (first space), S2...electron extraction space (second space), S3...processing space (third space), V1...first voltage level, V2...second voltage level, Vd...DC voltage, Vion...ionization voltage, Vp...pulse voltage, W...substrate.

Claims

1. a processing vessel defining an interior space including a first space, a second space, and a third space; a first gas supply unit configured to supply a first gas to the first space; a plasma generating unit configured to generate plasma of the first gas in the first space; a second gas supply unit configured to supply a second gas to the second space; a substrate support provided in the third space; a mesh member disposed between the first space and the second space, the mesh member having a plurality of through holes for selectively transmitting electrons in the plasma generated in the first space to the second space; a collector plate disposed between the second space and the third space and having a plurality of through holes communicating the second space with the third space; an energy supply unit that applies a pulse voltage between the mesh member and the collector plate to supply energy to the electrons in the second space and irradiates the second gas with the electrons to which energy has been supplied, thereby generating radicals for substrate processing from the second gas; Equipped with the pulse voltage periodically fluctuates between a first voltage level and a second voltage level, and when a voltage level for increasing the kinetic energy of the electrons to an energy threshold for ionizing the second gas is defined as an ionization voltage, the first voltage level is a voltage level lower than the ionization voltage, and the second voltage level is a voltage level higher than the ionization voltage. Substrate processing equipment.

2. The substrate processing apparatus according to claim 1 , wherein the pulse voltage has a pulse width and a duty ratio that do not ignite plasma of the second gas in the second space.

3. The mesh member further includes a second mesh member separate from the first mesh member, the second mesh member is disposed between the first mesh member and the collector plate; The energy supply unit is a DC power supply that applies a DC voltage between the first mesh member and the second mesh member so that the potential of the first mesh member is lower than the potential of the second mesh member; a variable DC power supply that applies a pulsed DC voltage between the second mesh member and the collector plate so that the potential of the second mesh member is lower than the potential of the collector plate; The substrate processing apparatus of claim 1 , comprising:

4. The substrate processing apparatus according to claim 3 , wherein the opening ratio of the first mesh member is lower than the opening ratio of the second mesh member.

5. The substrate processing apparatus of claim 1 , wherein the collector plate is electrically grounded.

6. The substrate processing apparatus of claim 1 , wherein the first gas comprises a rare gas.

7. The substrate processing apparatus of claim 1 , wherein the second gas comprises hydrogen gas.

8. 8. The substrate processing apparatus of claim 7, wherein the first voltage level is lower than a voltage level for setting the kinetic energy of the electrons to 13.6 eV, and the second voltage level is higher than a voltage level for setting the kinetic energy of the electrons to 13.6 eV.

9. 1. A substrate processing method for processing a substrate in a processing vessel defining an internal space including a first space, a second space, and a third space, comprising: generating plasma of a first gas in the first space; a step of applying a pulse voltage between a mesh member disposed between the first space and the second space and having a plurality of through holes for selectively transmitting electrons in the plasma generated in the first space to the second space, and a collector plate disposed between the second space and the third space and having a plurality of through holes communicating the second space with the third space, thereby supplying energy to the electrons that have transmitted through the mesh member; supplying a second gas into the second space and irradiating the second gas with the electrons to which energy has been supplied to generate radicals from the second gas; treating the substrate placed in the third space using the radicals; Including, the pulse voltage periodically fluctuates between a first voltage level and a second voltage level, and when a voltage level for increasing the kinetic energy of the electrons to an energy threshold for ionizing the second gas is defined as an ionization voltage, the first voltage level is a voltage level lower than the ionization voltage, and the second voltage level is a voltage level higher than the ionization voltage. Substrate processing method.

10. 10. The substrate processing method according to claim 9, wherein the pulse voltage has a pulse width and a duty ratio that do not ignite plasma of the second gas in the second space.

11. The substrate processing method of claim 9 , wherein the first gas comprises a noble gas.

12. The substrate processing method of claim 9 , wherein the second gas comprises hydrogen gas.

13. 13. The substrate processing method of claim 12, wherein the first voltage level is lower than a voltage level for setting the kinetic energy of the electrons to 13.6 eV, and the second voltage level is higher than a voltage level for setting the kinetic energy of the electrons to 13.6 eV.

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