Plasma processing device and plasma processing method

Abstract

This plasma processing device includes: a processing container; a placement table on which a substrate is placed inside the processing container; and an upper electrode provided at a position separated from the placement table. The upper electrode includes: a dielectric plate; and an electrode plate which is layered on the dielectric plate and to which high-frequency power is supplied. A cooling mechanism for cooling the electrode plate is connected to the electrode plate. A heat-transfer gas supply space is formed between the electrode plate and the dielectric plate. Furthermore, the plasma processing device includes: a heat transfer adjustment unit that adjusts the thermal conductivity of a heat-transfer gas supplied to the heat transfer gas supply space; and a control unit that controls the heat transfer adjustment unit.

Description

Plasma processing apparatus and plasma processing method

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

[0002] Patent Document 1 discloses a plasma processing apparatus that includes a processing vessel and a susceptor (mounting table) provided inside the processing vessel, and performs plasma processing on a substrate placed on the mounting table. This plasma processing apparatus fills a cavity inside the mounting table with an inert gas and generates a discharge, causing the plasma in the cavity to act as a dielectric, thereby controlling the distribution of plasma density during plasma processing.

[0003] In this type of plasma processing apparatus, the temperature of the upper electrode rises as heat is transferred from the plasma generated inside the processing chamber to the upper electrode, and therefore the plasma processing apparatus is usually equipped with a cooling mechanism (such as a cooling plate) for cooling the upper electrode.

[0004] JP 2009-123929 A

[0005] The present disclosure provides a technique that can effectively suppress a temperature rise in an upper electrode during plasma processing.

[0006] According to one aspect of the present disclosure, there is provided a plasma processing apparatus including a processing vessel, a mounting table for mounting a substrate inside the processing vessel, and an upper electrode located at a position away from the mounting table, and which performs plasma processing on the substrate inside the processing vessel by supplying high-frequency power to the upper electrode, wherein the upper electrode has a dielectric plate and an electrode plate stacked on the dielectric plate and to which the high-frequency power is supplied, a cooling mechanism for cooling the electrode plate is connected to the electrode plate, a heat transfer gas supply space is formed between the electrode plate and the dielectric plate, and the plasma processing apparatus is provided with a heat transfer adjustment unit for adjusting the thermal conductivity of the heat transfer gas supplied to the heat transfer gas supply space, and a control unit for controlling the heat transfer adjustment unit.

[0007] According to one aspect, it is possible to effectively suppress a temperature rise of the upper electrode during plasma processing.

[0008] FIG. 1 is a schematic cross-sectional view showing an example of a plasma processing apparatus according to a first embodiment. FIG. 2 is a cross-sectional view of the shower plate of FIG. 1 taken along line II-II. FIG. 3 is a side cross-sectional view showing an enlarged view of a shower head of the plasma processing apparatus and its periphery. FIG. 4 is an explanatory view illustrating the movement of molecules of a heat transfer gas in a molecular flow region. FIG. 5 is an explanatory view illustrating the movement of molecules of a heat transfer gas in a viscous flow region. FIG. 6 is a flowchart showing a plasma processing method. FIG. 7 is a cross-sectional view showing the flow of processing gas and the transfer of heat during plasma processing. FIG. 8 is a cross-sectional view showing the configuration of a shower plate and its periphery of a plasma processing apparatus according to a second embodiment. FIG. 9 is a cross-sectional view showing the configuration of a shower plate and its periphery of a plasma processing apparatus according to a third embodiment.

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant explanations may be omitted.

[0010] As shown in FIG. 1 , a plasma processing apparatus 1 according to the first embodiment includes a processing chamber 10, a stage 20 provided inside the processing chamber 10, and a shower head 30 provided above the stage 20. The plasma processing apparatus 1 supplies a processing gas from the shower head 30 and generates plasma from the processing gas, thereby performing plasma processing on a substrate W placed on the stage 20. The plasma processing performed by the plasma processing apparatus 1 is not particularly limited, and examples thereof include film formation processing, etching processing, cleaning processing, and ashing processing. The substrate W to be subjected to plasma processing is, for example, a silicon wafer or a compound semiconductor wafer. A recess pattern such as a trench or a via may be formed on the surface of the substrate W.

[0011] The processing vessel 10 has a substantially cylindrical shape, assembling the upper and lower concave vessels 11 and 12 by stacking the openings of the upper and lower concave vessels 11 and 12 in the vertical direction. The processing vessel 10 also has a shower plate 31 (described later) that is part of a shower head 30 sandwiched between the upper and lower concave vessels 11 and 12. The upper and lower concave vessels 11 and 12 are made of a metal material such as aluminum or an aluminum alloy, and are grounded via electric wires.

[0012] The lower concave vessel 12 has a substantially circular bottom wall 121 and an annular side wall 122 protruding upward from the side edge of the bottom wall 121, with the stage 20 installed inside these walls. The space surrounded by the bottom wall 121, the side wall 122, the stage 20, and the shower head 30 forms a plasma processing space 12s in which plasma processing is performed on a substrate W. The lower concave vessel 12 also has, in the side wall 122, a load / unload port 13 for loading and unloading the substrate W between it and the stage 20, and a gate valve 14 for opening and closing the load / unload port 13.

[0013] Furthermore, the lower concave vessel 12 has an exhaust port 23 at an appropriate position on the bottom wall 121 for exhausting gas from the plasma processing space 12s. In the plasma processing apparatus 1, an exhaust pipe 24 is connected to the exhaust port 23, and an exhaust device 25 is attached to the exhaust pipe 24. The exhaust device 25 has a pressure control valve and a vacuum pump such as a turbomolecular pump (not shown). In the plasma processing apparatus 1, the exhaust device 25 uses a suction operation to exhaust gas from the plasma processing space 12s of the processing vessel 10 to the outside of the processing vessel 10 through the exhaust port 23 and the exhaust pipe 24. This allows the plasma processing apparatus 1 to reduce the pressure in the plasma processing space 12s to a vacuum atmosphere and perform plasma processing in this vacuum atmosphere.

[0014] The stage 20 provided in the lower concave container 12 has a mounting table 21 on which the substrate W is placed, and a support shaft 22 that supports the center of the mounting table 21. The mounting table 21 and the support shaft 22 are made of metal such as aluminum.

[0015] The mounting table 21 is connected to a power supply (not shown) and includes an electrostatic chuck (not shown) that fixes the substrate W by electrostatic attraction. Note that the means for fixing the substrate W is not limited to electrostatic attraction, and may be suction or mechanical fixing means. The mounting table 21 may also include a dielectric member that forms a lower electrode, a temperature adjustment unit such as a heater or a coolant flow path, a lifter unit that receives and transfers the substrate W, and the like.

[0016] The support shaft 22 is supported rotatably by a rotation mechanism (not shown) and movable up and down by a lifting mechanism (not shown). For example, the rotation mechanism rotates the support shaft 22 about its axis during plasma processing to rotate the substrate W placed on the mounting table 21. The lifting mechanism lifts and lowers the mounting table 21 when loading and unloading the substrate W, thereby assisting in placing and unloading the substrate W onto and from the mounting table 21. The stage 20 may be configured to be fixed to the processing vessel 10 so as not to be rotatable.

[0017] The upper concave vessel 11 has a substantially circular top plate 111 and an annular side wall 112 that protrudes downward from the side edge of the top plate 111. The top plate 111 and the side wall 112 accommodate the shower head 30, a cooling mechanism 40 that cools the shower head 30, a resonator (not shown), and the like.

[0018] The shower head 30 is installed vertically above the stage 20 so as to face the stage 20, and supplies a processing gas to a substrate W placed on the stage 20. For example, the shower head 30 includes, in this order from bottom to top in the vertical direction, a shower plate 31, a dielectric plate 32, and an electrode plate 33. The dielectric plate 32 and the electrode plate 33 are in contact with each other and stacked to form an upper electrode 34 of the plasma processing apparatus 1. The cooling mechanism 40 also includes a cooling plate 41 stacked on the shower head 30 (electrode plate 33).

[0019] The shower plate 31 is formed in a disk shape with approximately the same diameter as the top plate 111 of the upper concave vessel 11 (and the bottom wall 121 of the lower concave vessel 12). As described above, the shower plate 31 is sandwiched and fixed between the upper concave vessel 11 and the lower concave vessel 12. Sealing parts (not shown) that can airtightly seal the inside of the processing vessel 10 may be provided between the upper concave vessel 11 and the shower plate 31, and between the lower concave vessel 12 and the shower plate 31. The shower plate 31 is formed of a metal material such as aluminum, nickel, a nickel alloy, or stainless steel.

[0020] The shower plate 31 includes gas flow paths 311 through which a process gas can flow in the horizontal direction, an inlet port 312 that introduces the process gas into the gas flow paths 311, and a plurality of gas outlets 313 that communicate with the gas flow paths 311 and open on the upper surface of the shower plate 31. The shower plate 31 further includes a plurality of through holes 314 that are arranged in line with the gas outlets 313 and that penetrate the shower plate 31 between the upper surface and the lower surface.

[0021] 2 , the gas flow path 311 is formed by an internal space surrounded by the outer peripheral wall 31cf of the shower plate 31. A plurality of cylindrical walls 315 surrounding each through-hole 314 are provided inside the shower plate 31, and the portion excluding these cylindrical walls 315 constitutes the gas flow path 311. The gas flow path 311 thus formed can move the process gas introduced from the inlet port 312 in the horizontal direction while diffusing it, thereby causing the process gas to flow into each gas discharge port 313. Note that the gas flow path 311 is not limited to this internal space, and may have various flow path shapes (e.g., lattice-shaped, annular, spiral, etc.) that can uniformly discharge the process gas from each gas discharge port 313.

[0022] A plurality of introduction ports 312 are provided in the circumferential direction of the outer peripheral wall 31cf of the shower plate 31, and their internal flow paths communicate with the gas flow paths 311. The introduction ports 312 protrude horizontally outward from the processing vessel 10, and a gas supply unit 50 that supplies a processing gas is connected to the protruding end of each introduction port 312 (see FIG. 1). Note that while FIG. 2 illustrates the shower plate 31 with two introduction ports 312, the number of introduction ports 312 is not particularly limited and may be one, or three or more.

[0023] Returning to FIG. 1 , the plasma processing apparatus 1 has a gas supply unit 50 for supplying a process gas connected to each inlet port 312 protruding from the processing chamber 10. The gas supply unit 50 has a supply path 51 for circulating a process gas (such as a source gas, a reactive gas, an etching gas, or an inert gas) outside the plasma processing apparatus 1. The gas supply unit 50 also has a flow rate regulator 52, an on-off valve 53, a process gas supply source 54, and other components installed on the supply path 51. The flow rate regulator 52 is implemented by a mass flow controller or the like, and adjusts the flow rate of the process gas supplied from the supply source 54 under the control of the control unit 90. The on-off valve 53 opens and closes the flow path of the supply path 51 under the control of the control unit 90, thereby switching between supply and stop of the process gas.

[0024] 3, the shower plate 31 separates a plasma processing space 12s in the lower concave vessel 12 from a plasma generation space 11s formed between the shower plate 31 and the dielectric plate 32 in the upper concave vessel 11. During plasma processing, the distance H1 between the shower plate 31 and the mounting table 21 (the distance of the plasma processing space 12s) is set to, for example, within a range of approximately 10 mm to 20 mm.

[0025] The gas outlets 313 of the shower plate 31 are formed on the upper surface (plasma generation space 11s) of the shower plate 31, but not on the lower surface (plasma processing space 12s) of the shower plate 31. In other words, the shower plate 31 discharges the processing gas through the gas outlets 313 toward the plasma generation space 11s, which is on the opposite side from the plasma processing space 12s (between the shower plate 31 and the dielectric plate 32). This allows the processing gas discharged from the shower plate 31 to be converted into plasma by high-frequency power applied by the dielectric plate 32, while diffusing the processing gas in the plasma generation space 11s.

[0026] Meanwhile, each through-hole 314 of the shower plate 31 is surrounded by a cylindrical wall 315 and penetrates the shower plate 31 in the thickness direction, thereby connecting the plasma generation space 11s and the plasma processing space 12s. Therefore, the shower plate 31 allows the processing gas that has been diffused and converted into plasma to flow from the plasma generation space 11s toward the plasma processing space 12s. For example, each through-hole 314 is provided between adjacent gas ejection ports 313, so that the number of through-holes 314 is approximately the same as the number of gas ejection ports 313. The gas ejection ports 313 and the through-holes 314 can be arranged in any suitable pattern, such as a matrix, a radial pattern, or a concentric pattern.

[0027] The dielectric plate 32, which is one of the upper electrodes 34, is spaced from the shower plate 31 by a set distance H2, thereby forming the plasma generation space 11s. The distance H2 between the shower plate 31 and the dielectric plate 32 (the distance of the plasma generation space 11s) can be set, for example, in the range of approximately 2 mm to 10 mm. The dielectric plate 32 is formed in a disk shape that is thinner than the shower plate 31. The dielectric plate 32 is fixed to the upper electrode plate 33 by an appropriate fixing structure such as welding or screwing, and is supported so as to be approximately horizontal within the processing vessel 10. The dielectric plate 32 is preferably formed from a metal material having a high dielectric constant, such as alumina, zirconia, or yttria.

[0028] The electrode plate 33, which is the other of the upper electrodes 34, is formed in a block shape that is thicker than the dielectric plate 32, and supports the dielectric plate 32 on its underside. The underside of the electrode plate 33 is formed as a curved surface 33c (arc-shaped in cross section) that is recessed vertically upward from the outer periphery on the radially outer side toward the center. The electrode plate 33 fixes and supports the outer periphery of the dielectric plate 32 on its outer periphery. In contrast, the portion of the electrode plate 33 radially inward from the outer periphery is spaced upward from the dielectric plate 32 in accordance with the curved surface 33c, thereby forming a heat transfer gas supply space 35 between the electrode plate 33 and the horizontally extending dielectric plate 32.

[0029] The electrode plate 33 has a curved surface 33c to suppress the effects of standing waves generated by the high frequency (short wavelength) of the high-frequency power applied to the electrode plate 33. In other words, the electrode plate 33 has a curved surface 33c with a constant curvature, which changes the gap between the electrode plate 33 and the dielectric plate 32 in the radial direction, thereby changing the electrostatic capacitance along the radial direction. This allows the upper electrode 34 (dielectric plate 32, electrode plate 33) to cancel the electric field intensity distribution of the standing wave. In addition, a heat transfer gas is supplied to a heat transfer gas supply space 35 between the dielectric plate 32 and the electrode plate 33. The configuration for supplying this heat transfer gas will be described in detail later.

[0030] 1 , in the plasma processing apparatus 1, a power supply member 36 is connected to an appropriate position on the electrode plate 33. The power supply member 36 protrudes upward from within the processing chamber 10 through the top plate 111 of the upper concave chamber 11 and is connected to an external power supply unit 70.

[0031] The power supply unit 70 supplies high-frequency power to the electrode plate 33. The power supply unit 70 includes, for example, a wiring 71 connected to the power supply member 36, and a high-frequency power supply 72 and a matching box 73 provided on the wiring 71.

[0032] The power supply unit 70 supplies VHF band high-frequency power from the high-frequency power supply 72 to the electrode plate 33 via a matching box 73. As a result, VHF power is also supplied to the dielectric plate 32 fixed to the electrode plate 33. The dielectric plate 32 generates plasma from the processing gas supplied to the plasma generation space 11s, thereby supplying activated species such as radicals and ions in the plasma from the plasma generation space 11s to the plasma processing space 12s. The frequency of the VHF high-frequency power supplied from the high-frequency power supply 72 is, for example, 30 MHz to 300 MHz. However, the frequency of the high-frequency power is not limited to this, and may be 13 MHz to 30 MHz or a UHF band frequency of 300 MHz to 3 GHz.

[0033] The cooling plate 41 of the cooling mechanism 40 is stacked on top of the electrode plate 33, thereby cooling (removing heat from) the electrode plate 33 that is in contact with the cooling plate 41 during plasma processing or the like. The cooling plate 41 has a coolant flow path 41a therein, and also has a pump for circulating the coolant through the coolant flow path and a chiller or the like (both not shown) for exchanging heat with the coolant, both of which are located outside the processing vessel 10. Note that the cooling mechanism 40 is not limited to such a configuration for circulating a coolant, and various configurations (such as heat dissipation fins or an air-based cooling mechanism) may be employed.

[0034] The plasma processing apparatus 1 according to the first embodiment includes a heat transfer gas supply mechanism 60 that supplies a heat transfer gas to the heat transfer gas supply space 35 between the dielectric plate 32 and the electrode plate 33 that constitute the upper electrode 34. The heat transfer gas supplied by the heat transfer gas supply mechanism 60 may be selected to have high thermal conductivity, such as helium (He) gas or hydrogen (H ２ The heat transfer gas supplied to the heat transfer gas supply space 35 is sealed in the heat transfer gas supply space 35 and then discharged from a dedicated exhaust part 67 for discharging the heat transfer gas. Note that if the heat transfer gas is supplied to the plasma generation space 11s, it will affect the plasma generated in the plasma generation space 11s, so it is desirable that the exhaust part 67 does not pass through the plasma generation space 11s.

[0035] The heat transfer gas supply mechanism 60 has a heat transfer gas supply pipe 61 that is provided to penetrate the processing vessel 10 (top plate 111 of the upper concave vessel 11). One end of the heat transfer gas supply pipe 61 is located at the center (top) of the curved surface 33c and opens into the heat transfer gas supply space 35. The heat transfer gas supply pipe 61 extends vertically upward from this one end to penetrate the cooling plate 41 and the electrode plate 33, and the other end protrudes from the top plate 111 of the upper concave vessel 11.

[0036] The heat transfer gas supply mechanism 60 connects a heat transfer gas path 62 to the other end of the heat transfer gas supply pipe 61. The heat transfer gas supply mechanism 60 has a flow rate regulator 63, a pressure adjustment valve 64, a heat transfer gas source 65, and the like installed at appropriate positions on the heat transfer gas path 62. The flow rate regulator 63 is equipped with a mass flow controller or the like and is connected to a control unit 90, which adjusts the flow rate of the heat transfer gas supplied from the heat transfer gas source 65 to the heat transfer gas supply space 35 under the control of the control unit 90.

[0037] The pressure regulating valve 64 is also connected to the control unit 90, and under the control of the control unit 90, opens and closes the flow path of the heat transfer gas path 62 to switch between supplying and stopping the heat transfer gas from the heat transfer gas path 62, and adjusts the opening degree to adjust the supply pressure. The heat transfer gas supply mechanism 60 changes the thermal conductivity of the heat transfer gas in the heat transfer gas supply space 35 by adjusting the supply pressure (internal pressure) of the heat transfer gas with the pressure regulating valve 64. Therefore, the pressure regulating valve 64, which adjusts the supply pressure of the heat transfer gas, functions as a heat transfer adjusting unit that adjusts the thermal conductivity of the heat transfer gas in the heat transfer gas supply space 35.

[0038] During plasma processing, the heat transfer gas supply mechanism 60 described above supplies heat transfer gas to the heat transfer gas supply space 35 via the heat transfer gas path 62 and the heat transfer gas supply pipe 61, thereby filling the heat transfer gas supply space 35 with heat transfer gas. This increases the thermal conductivity between the dielectric plate 32 and the electrode plate 33, and enables the heat of the dielectric plate 32, generated by plasma generation, to be smoothly transferred to the electrode plate 33.

[0039] The heat transfer gas supply mechanism 60 also includes a pressure sensor 66 in the heat transfer gas path 62 downstream of the pressure adjustment valve 64. The pressure sensor 66 detects the pressure of the heat transfer gas in the heat transfer gas supply space 35 via the heat transfer gas path 62 and the heat transfer gas supply pipe 61 and transmits the detected information to the control unit 90. The control unit 90 can adjust the pressure in the heat transfer gas supply space 35 to a target pressure by controlling the opening degree of the pressure adjustment valve 64 based on the detected information from the pressure sensor 66. Note that the pressure sensor 66 may have a detector that actually detects pressure and is installed in the heat transfer gas supply space 35.

[0040] Here, it is desirable that the plasma processing apparatus 1 controls the target pressure of the heat transfer gas in the heat transfer gas supply space 35 to a value that maximizes the thermal conductivity. The relationship between the supply state of the heat transfer gas and the thermal conductivity will be described below with reference to FIGS. 4A and 4B.

[0041] Specifically, the flow state of a gas (heat transfer gas) can be classified into a viscous flow region, a molecular flow region, and an intermediate flow region where these viscous and molecular flow regions coexist. In the viscous flow region, as shown in Figure 4A, a large number of heat transfer gas molecules in a given space results in fewer regions (vacuums) where no molecules are present. Although the vacuum region is an adiabatic state, when heat transfer gas molecules are close to each other, heat can be transferred between nearby molecules, reducing heat transfer losses. In other words, this region is where the thermal conductivity within the space is high. In the molecular flow region, as shown in Figure 4B, a small number of heat transfer gas molecules in a given space results in larger regions (vacuums) where no molecules are present. Because the heat transfer gas molecules are farther apart, heat cannot be transferred between molecules. The heat transfer gas molecules must move, and the energy lost during this movement affects heat transfer. In other words, this region is where the thermal conductivity within the space is low. The viscous flow region, molecular flow region, and intermediate flow region are determined using the dimensionless Knudsen number (Kn) as an index. The Knudsen number can be expressed by the following equation (1):

[0042] In equation (1), λ is the mean free path, and L is the characteristic length (the gap between the dielectric plate 32 and the electrode plate 33). In other words, the Knudsen number is calculated as the ratio of the characteristic length L to the mean free path λ. As shown in equation (1), the mean free path λ is calculated using the Boltzmann constant k Ｂ , absolute temperature T, molecular diameter δ, and total pressure P (pressure in the heat transfer gas supply space 35).

[0043] The viscous flow region is a region where the Knudsen number Kn is less than 0.01. The molecular flow region is a region where the Knudsen number Kn is greater than 0.3. The intermediate flow region is a region where the Knudsen number Kn is between 0.01 and 0.3 (0.01≦Kn≦0.3). In other words, the thermal conductivity of the heat transfer gas can be increased as it approaches the viscous flow region from the molecular flow region within the intermediate flow region, and further, in the viscous flow region, heat can be transferred at a substantially constant thermal conductivity.

[0044] Returning to FIG. 1 , the control unit 90 of the plasma processing apparatus 1 acquires detection information from the pressure sensor 66 and monitors the pressure in the heat transfer gas supply space 35 during supply of the heat transfer gas. The control unit 90 then adjusts the supply pressure using the pressure adjustment valve 64 so that the heat transfer gas supply space 35 is in a viscous flow region or approaches the viscous flow region in the intermediate flow region. This allows the heat transfer gas supplied to the heat transfer gas supply space 35 to efficiently transfer heat from the dielectric plate 32 to the electrode plate 33. In other words, by adjusting the supply pressure of the heat transfer gas so that the heat transfer gas in the heat transfer gas supply space 35 is in a viscous flow region (or approaches the viscous flow region in the intermediate flow region), the plasma processing apparatus 1 can effectively remove heat from the dielectric plate 32, which has risen in temperature due to the heat input of plasma.

[0045] As described above, the cooling plate 41 is stacked above the electrode plate 33, and the cooling plate 41 cools the electrode plate 33. Therefore, even if heat from the plasma generated in the plasma generation space 11s enters the dielectric plate 32, the heat can be dissipated in this order from the electrode plate 33 to the cooling plate 41 via the heat transfer gas in the heat transfer gas supply space 35. As a result, deformation of the dielectric plate 32 due to heat, etc. is suppressed, making it possible to stabilize the electric field strength distribution of the plasma.

[0046] The control unit 90 of the plasma processing apparatus 1 has a control unit 91 and a user interface 95, and controls each component of the plasma processing apparatus 1. The control unit 91 can be a computer having a processor 92, a memory 93, and an input / output interface and a communication interface (not shown). The processor 92 is one or a combination of a central processing unit (CPU), a graphics processing unit (GPU), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a circuit made up of multiple discrete semiconductors, and executes programs stored in the memory 93. The memory 93 includes a main storage device made up of a semiconductor memory or the like, and an auxiliary storage device made up of a disk, semiconductor memory (flash memory), or the like.

[0047] The user interface 95 is a device connected to the input / output interface of the control body 91, and provides information to the user and accepts input from the user. The user interface 95 is not particularly limited, but examples thereof include a touch panel, a monitor, a keyboard, a mouse, a speaker, a microphone, etc.

[0048] For example, when performing a film formation process, the control unit 90 first supplies a raw material gas from the shower plate 31 and circulates the raw material gas through the plasma generation space 11s, each through-hole 314, and the plasma processing space 12s in this order, thereby adsorbing the raw material gas onto the substrate W. At this time, the control unit 90 does not supply VHF power. Therefore, the raw material gas is adsorbed onto the surface of the substrate W without being converted into plasma. Then, the plasma processing apparatus 1 supplies a reactive gas to the plasma generation space 11s from the shower plate 31. At this time, the plasma processing apparatus 1 converts the reactive gas into plasma in the plasma generation space 11s by supplying VHF power to the upper electrode 34 (electrode plate 33, dielectric plate 32) from the power supply unit 70. The reactive gas and activated species in the plasma are introduced into the plasma processing space 12s through the through-holes 314. In this way, the plasma processing apparatus 1 reacts the raw material gas adsorbed on the substrate W with the reactive gas, thereby forming a desired film on the surface of the substrate W.

[0049] As described above, in the plasma processing apparatus 1, the gas discharge ports 313 of the shower plate 31 are formed facing upward. This makes it difficult for the pattern of the gas discharge ports 313 to be transferred to a film even when the spacing H1 of the plasma processing space 12s is in the range of approximately 10 mm to 20 mm, thereby ensuring uniformity in substrate processing.

[0050] The plasma processing apparatus 1 according to the first embodiment is basically configured as described above, and its operation (plasma processing method) will be described below with reference to FIGS.

[0051] When performing plasma processing, the control unit 90 of the plasma processing apparatus 1 executes steps S101 to S107 shown in FIG.

[0052] Before performing plasma processing, the control unit 90 controls the heat transfer gas supply mechanism 60 to supply a heat transfer gas to the heat transfer gas supply space 35 of the upper electrode 34 (step S101). At this time, the control unit 90 controls the pressure adjustment valve 64, which is a heat transfer adjustment unit, while monitoring the detection information (pressure in the heat transfer gas supply space 35) detected by the pressure sensor 66, to adjust the supply pressure of the heat transfer gas supplied to the heat transfer gas supply space 35. In this way, the control unit 90 can maintain the pressure in the heat transfer gas supply space 35 constant at a target pressure.

[0053] Specifically, the control unit 90 controls the pressure adjustment valve 64 so that the heat transfer gas contains viscous flow. For example, the control unit 90 adjusts the supply pressure of the heat transfer gas using the pressure adjustment valve 64 to increase the pressure in the heat transfer gas supply space 35, thereby setting the Knudsen number to less than 0.01. This provides high thermal conductivity in the heat transfer gas supply space 35 and allows smooth heat transfer in the upper electrode 34. Note that even in the intermediate flow region, some of the heat transfer gas in the heat transfer gas supply space 35 is in viscous flow, which allows for increased thermal conductivity. Therefore, the Knudsen number may be 0.3 or less. Conversely, if the Knudsen number exceeds 0.3, heat transfer is reduced, resulting in a decrease in the heat removal efficiency of the dielectric plate 32.

[0054] Then, during the supply of the heat transfer gas, the control unit 90 determines whether the pressure in the heat transfer gas supply space 35 has reached or exceeded the target pressure based on the detection information from the pressure sensor 66 (step S102). If the pressure in the heat transfer gas supply space 35 has reached or exceeded the target pressure (step S102: YES), the control unit 90 proceeds to step S103, but if the pressure in the heat transfer gas supply space 35 is below the target pressure, the control unit 90 continues with step S101.

[0055] In step S103, the control unit 90 controls the gas supply unit 50 to discharge the process gas from the shower plate 31 and the power supply unit 70 to supply high-frequency power to the upper electrode 34, thereby performing plasma processing on the substrate W (step (A)). As shown in FIG. 6 , the shower plate 31 discharges the process gas into the plasma generation space 11s between the shower plate 31 and the dielectric plate 32. Therefore, the dielectric plate 32 of the upper electrode 34, to which high-frequency power is supplied, can effectively generate plasma for the process gas in the plasma generation space 11s. The plasma generated in the plasma generation space is then supplied to the plasma processing space 12s via the through-holes 314 of the shower plate 31. As a result, the substrate W supported on the mounting table 21 in the plasma processing space 12s is subjected to plasma processing.

[0056] As described above, the electrode plate 33 has a curved surface 33c with a constant curvature on the surface facing the dielectric plate 32, thereby canceling the electric field intensity distribution of standing waves when high-frequency power is supplied, thereby enabling the upper electrode 34 to effectively generate plasma from the processing gas supplied to the plasma generation space 11s.

[0057] 5 , upon start of plasma processing, the control unit 90 operates the cooling mechanism 40 to circulate the coolant through the coolant flow path 41 a of the cooling plate 41, thereby cooling the upper electrode 34 (step S104: (B)). Note that cooling by the cooling mechanism 40 may be performed before the start of plasma processing, or may be performed when the temperature of the upper electrode 34 reaches or exceeds a predetermined value after the start of plasma processing.

[0058] The control unit 90 monitors the pressure in the heat transfer gas supply space 35 using the pressure sensor 66 even during plasma processing, and adjusts the supply pressure of the heat transfer gas to maintain the pressure in the heat transfer gas supply space 35 at the target pressure (step S105: (B)). That is, as described above, the heat transfer gas in the heat transfer gas supply space 35 is discharged from the discharge unit 67, but the control unit 90 monitors the pressure of this discharged heat transfer gas and supplies heat transfer gas, thereby maintaining a constant pressure in the heat transfer gas supply space 35. This allows the heat transfer gas in the heat transfer gas supply space 35 to remain in the viscous flow region (or close to the viscous flow region in the intermediate flow region), in other words, to maintain a state including a viscous flow.

[0059] As shown in FIG. 6 , plasma is generated in the plasma generation space 11s inside the processing vessel 10 by plasma processing. Therefore, the dielectric plate 32 exposed to the plasma generation space 11s receives heat input from the plasma. The upper electrode 34 transfers the heat of the plasma input to the dielectric plate 32 to the heat transfer gas supply space 35, which contains a viscous flow of heat transfer gas. That is, the heat transfer gas in the heat transfer gas supply space 35 has high thermal conductivity due to its viscous flow, allowing for smooth heat removal from the dielectric plate 32. Furthermore, the electrode plate 33 is cooled by the cooling plate 41 of the cooling mechanism 40, allowing the heat of the dielectric plate 32 to be recovered by the cooling plate 41. For example, while the temperature of the dielectric plate 32 may rise to 300°C or higher during plasma generation, the plasma processing apparatus 1 can suppress this temperature to approximately 100 to 200°C by removing heat through the heat transfer gas supply space 35. Since the temperature of the dielectric plate 32 is suppressed even during plasma processing, deformation due to heat can be suppressed.

[0060] During the execution of the plasma processing, the control unit 90 monitors whether the plasma processing should be terminated (step S106). For example, the control unit 90 compares the actual duration of the plasma processing with a target period preset in a plasma processing recipe or the like. If the duration has not reached the target period, the control unit 90 determines to continue the plasma processing (step S106: NO), returns to step S103, and repeats the same processing flow. On the other hand, if the duration has reached the target period, the control unit 90 determines to terminate the plasma processing (step S106: YES), and proceeds to step S107.

[0061] In step S107, the control unit 90 stops the supply of the processing gas and the supply of the high-frequency power, and performs post-processing by stopping the supply of the heat transfer gas, thereby completing the plasma processing of the substrate W. Note that the control unit 90 may continue the supply of the heat transfer gas for an appropriate period of time even after the supply of the high-frequency power has been stopped. This allows the plasma processing apparatus 1 to promote cooling of the plasma generation space 11s, which is in a high-temperature state. In other words, the control of the heat transfer gas in the heat transfer gas supply space 35 to include a viscous flow may be performed in a state in which plasma is not being generated.

[0062] The plasma processing apparatus 1 and plasma processing method according to the present disclosure are not limited to the above-described embodiment and may take various forms. For example, the plasma processing apparatus 1 according to the first embodiment has a configuration in which the shower plate 31 and the upper electrode 34 are spaced apart, but the configuration is not limited thereto and the shower plate 31 and the upper electrode 34 may be stacked (contacted).

[0063] 7 differs from the plasma processing apparatus 1 described above in that the pressure of the heat transfer gas in the heat transfer gas supply space 35 is adjusted from the exhaust unit 67A side. Specifically, the exhaust unit 67A connects an exhaust path 671 to the heat transfer gas passage 62, and a back pressure adjustment valve 68 is installed in the exhaust path 671. Note that the exhaust path 671 may be directly connected to the heat transfer gas supply space 35. The back pressure adjustment valve 68 adjusts the valve opening based on the control of the control unit 90 to adjust the pressure in the heat transfer gas supply space 35, which is connected via the exhaust path 671.

[0064] The control unit 90 supplies the entire amount (or a set flow rate) of heat transfer gas to the heat transfer gas supply space 35 using the flow rate regulator 63, for example. During the supply of heat transfer gas, the control unit 90 monitors the detection information from the pressure sensor 66 and executes feedback control to adjust the aperture of the back pressure adjustment valve 68 so that the pressure in the heat transfer gas supply space 35 reaches the target pressure. This causes the heat transfer gas in the heat transfer gas supply space 35 to enter a viscous flow region (or approach the viscous flow region in the intermediate flow region), enabling good heat transfer.

[0065] Alternatively, the control unit 90 may be provided with a differential pressure gauge 69 that detects the differential pressure between the pressure in the heat transfer gas supply space 35 (heat transfer gas path 62) and the pressure in the plasma generation space 11s, and may adjust the back pressure using the back pressure adjustment valve 68 based on information on the differential pressure from the differential pressure gauge 69. This makes it possible to appropriately suppress, for example, the influence (deformation, etc.) of the dielectric plate 32 that occurs when the pressure in the plasma generation space 11s is low while the pressure in the heat transfer gas supply space 35 is high.

[0066] A plasma processing apparatus 1B according to a third embodiment shown in FIG. 8 differs from the plasma processing apparatuses 1 and 1A in that it is configured to control the plasma distribution in real time by observing the plasma distribution through a heat transfer gas supply space 35. For example, the plasma processing apparatus 1B includes an observation unit 80 for observing the plasma distribution, which includes multiple transmission windows 81 penetrating the electrode plate 33 and optical detectors 82 installed at each of the transmission windows 81. Each transmission window 81 and each optical detector 82 is arranged radially around the electrode plate 33 and detects the plasma emission intensity at each position. The transmission windows 81 may be a waveguide (waveguide) that can suppress light loss from the optical detectors 82.

[0067] For example, during plasma generation, the control unit 90 obtains the plasma emission intensity by emitting measurement light from each optical detector 82 and detecting the light reflected from the dielectric plate 32. The control unit 90 then controls the pressure in the heat transfer gas supply space 35 so as to minimize the difference in the obtained emission intensities of the optical detectors 82. This enables the plasma processing apparatus 1B to appropriately control the supply of the processing gas or the heat transfer gas while recognizing the plasma distribution state. Note that the means for observing the plasma distribution state is not limited to the above, and various configurations can of course be applied.

[0068] The technical ideas and effects of the present disclosure explained in the above embodiments will be described below.

[0069] A first aspect of the present disclosure is a plasma processing apparatus 1 including a processing vessel 10, a mounting table 21 on which a substrate W is placed inside the processing vessel 10, and an upper electrode 34 located at a position away from the mounting table 21, and which performs plasma processing on the substrate W inside the processing vessel 10 by supplying high-frequency power to the upper electrode 34, wherein the upper electrode 34 has a dielectric plate 32 and an electrode plate 33 stacked on the dielectric plate 32 and supplied with high-frequency power, a cooling mechanism 40 for cooling the electrode plate 33 is connected to the electrode plate 33, a heat transfer gas supply space 35 is formed between the electrode plate 33 and the dielectric plate 32, and the apparatus is equipped with a heat transfer adjustment unit (pressure adjustment valve 64) for adjusting the thermal conductivity of the heat transfer gas supplied to the heat transfer gas supply space 35, and a control unit 90 for controlling the heat transfer adjustment unit.

[0070] As described above, the plasma processing apparatus 1 can appropriately adjust the thermal conductivity of the heat transfer gas in the heat transfer gas supply space 35 formed between the electrode plate 33 and the dielectric plate 32 using the heat transfer adjustment unit (pressure adjustment valve 64). This allows the plasma processing apparatus 1 to effectively suppress a temperature rise in the upper electrode 34 during plasma processing. As a result, for example, the plasma processing apparatus 1 can suppress deformation of the dielectric plate 32 due to the heat of plasma processing, and can stably perform plasma processing on the substrate W.

[0071] Furthermore, the control unit 90 controls the heat transfer adjustment unit (pressure adjustment valve 64) so ​​that the heat transfer gas supplied to the heat transfer gas supply space 35 during plasma processing contains a viscous flow. This allows the plasma processing apparatus 1 to maintain a sufficiently high heat transfer coefficient of the heat transfer gas in the heat transfer gas supply space 35, making it possible to easily transfer heat from the dielectric plate 32 to the electrode plate 33.

[0072] Furthermore, when the heat transfer gas in the heat transfer gas supply space 35 contains a viscous flow, the Knudsen number of the heat transfer gas is 0.3 or less. This allows the plasma processing apparatus 1 to further increase the thermal conductivity of the heat transfer gas in the heat transfer gas supply space 35.

[0073] The heat transfer adjustment unit is a pressure adjustment valve 64 that adjusts the supply pressure of the heat transfer gas supplied to the heat transfer gas supply space 35. This allows the plasma processing apparatus 1 to easily adjust the pressure of the heat transfer gas in the heat transfer gas supply space 35.

[0074] The control unit 90 controls the pressure adjustment valve 64 based on the information detected by the pressure sensor 66 to adjust the flow rate of the heat transfer gas. This allows the plasma processing apparatus 1 to easily adjust the pressure of the heat transfer gas in the heat transfer gas supply space 35 to the target pressure.

[0075] Furthermore, the electrode plate 33 has a curved surface 33c with a constant curvature on the surface facing the dielectric plate 32, thereby forming a heat transfer gas supply space 35 between the electrode plate 33 and the dielectric plate 32. This curved surface 33c enables the plasma processing apparatus 1 to suppress the influence of standing waves of high frequency power and to improve the in-plane uniformity of the plasma.

[0076] In addition, a shower plate 31 that supplies a processing gas when performing plasma processing on a substrate is provided between the mounting table 21 and the dielectric plate 32. This allows the plasma processing apparatus 1 to easily generate plasma of the processing gas by discharging the processing gas from the shower plate 31 toward the dielectric plate 32. Furthermore, by supplying the processing gas from the shower plate 31, the plasma processing apparatus 1 makes it easier to increase the pressure in the heat transfer gas supply space 35 and obtain viscosity of the heat transfer gas.

[0077] The shower plate 31 also has a plurality of gas outlets 313 that discharge the processing gas toward the dielectric plate 32, and a plurality of through holes 314 that allow the processing gas to move from the space between the shower plate 31 and the dielectric plate 32 (plasma generation space 11s) to the space between the shower plate 31 and the mounting table 21 (plasma processing space 12s). This allows the plasma processing apparatus 1 to smoothly guide the plasma of the processing gas into the plasma processing space 12s after generating the plasma in the plasma generation space 11s.

[0078] The cooling mechanism 40 also includes a cooling plate 41 that is stacked on the electrode plate 33 and removes heat from the electrode plate 33. This allows the plasma processing apparatus 1 to easily cool the upper electrode 34 by transferring heat transferred from the dielectric plate 32 via the heat transfer gas supply space 35 to the cooling plate 41.

[0079] A second aspect of the present disclosure is a plasma processing method for a plasma processing apparatus 1 including a processing vessel 10, a mounting table 21 on which a substrate W is mounted inside the processing vessel 10, and an upper electrode 34 located at a position away from the mounting table 21, and which performs plasma processing on the substrate W inside the processing vessel 10 by supplying high-frequency power to the upper electrode 34, the method including: (A) supplying high-frequency power to an electrode plate 33 of the upper electrode 34 to generate plasma inside the processing vessel 10 via a dielectric plate 32 of the upper electrode 34 stacked on the electrode plate 33; and (B) during the step (A), cooling the electrode plate 33 with a cooling mechanism 40 connected to the electrode plate 33 and supplying a heat transfer gas to a heat transfer gas supply space 35 formed between the electrode plate 33 and the dielectric plate 32 to adjust the thermal conductivity of the heat transfer gas by causing the heat transfer gas to include a viscous flow. Even in this case, the plasma processing method can effectively suppress a temperature rise of the upper electrode during plasma processing.

[0080] The plasma processing apparatus 1 and plasma processing method according to the presently disclosed embodiments are illustrative in all respects and are not limiting. The embodiments can be modified and improved in various ways without departing from the spirit and scope of the appended claims. The features described in the above embodiments can be configured in other ways as long as they are not inconsistent, and can be combined as long as they are not inconsistent.

[0081] The plasma processing apparatus of the present disclosure can be applied to any type of apparatus, including atomic layer deposition (ALD) apparatus, capacitively coupled plasma (CCP), inductively coupled plasma (ICP), radial line slot antenna (RLSA), electron cyclotron resonance plasma (ECR), and helicon wave plasma (HWP).

[0082] This application claims priority from Japanese Patent Application No. 2024-011198, filed on January 29, 2024, with the Japan Patent Office, the entire contents of which are incorporated herein by reference.

[0083] REFERENCE SIGNS LIST 1 plasma processing apparatus 10 processing vessel 21 mounting table 32 dielectric plate 33 electrode plate 34 upper electrode 35 heat transfer gas supply space 64 pressure adjustment valve 90 control unit W substrate

Claims

1. A plasma processing apparatus comprising: a processing vessel; a mounting table on which a substrate is placed inside the processing vessel; and an upper electrode located at a position away from the mounting table, and configured to perform plasma processing on the substrate inside the processing vessel by supplying high frequency power to the upper electrode, wherein the upper electrode has: a dielectric plate; and an electrode plate stacked on the dielectric plate and supplied with the high frequency power, wherein a cooling mechanism for cooling the electrode plate is connected to the electrode plate, and a heat transfer gas supply space is formed between the electrode plate and the dielectric plate, and further comprising: a heat transfer adjustment unit for adjusting the thermal conductivity of the heat transfer gas supplied to the heat transfer gas supply space; and a control unit for controlling the heat transfer adjustment unit.

2. The plasma processing apparatus according to claim 1, wherein the control unit controls the heat transfer adjustment unit so that the heat transfer gas supplied to the heat transfer gas supply space contains a viscous flow during the plasma processing.

3. The plasma processing apparatus according to claim 2, wherein the state in which the heat transfer gas in the heat transfer gas supply space contains a viscous flow is a state in which the Knudsen number of the heat transfer gas is 0.3 or less.

4. The plasma processing apparatus according to any one of claims 1 to 3, wherein the heat transfer adjusting unit is a pressure adjusting valve that adjusts the supply pressure of the heat transfer gas supplied to the heat transfer gas supply space.

5. The plasma processing apparatus according to claim 4, further comprising a pressure sensor for detecting the pressure of the heat transfer gas in the heat transfer gas supply space, and the control unit controls the pressure regulating valve based on the detection information of the pressure sensor to adjust the supply pressure of the heat transfer gas.

6. A plasma processing apparatus according to any one of claims 1 to 3, wherein the surface of the electrode plate facing the dielectric plate is a curved surface with a constant curvature, thereby forming the heat transfer gas supply space between the electrode plate and the dielectric plate.

7. The plasma processing apparatus according to claim 1, further comprising a shower plate between the stage and the dielectric plate for supplying a processing gas when the plasma processing is performed on the substrate.

8. The plasma processing apparatus according to claim 7, wherein the shower plate has a plurality of gas outlets that eject the processing gas toward the dielectric plate, and a plurality of through holes that allow the processing gas to move from a space between the shower plate and the dielectric plate to a space between the shower plate and the mounting table.

9. The plasma processing apparatus according to any one of claims 1 to 3, wherein the cooling mechanism has a cooling plate that is stacked on the electrode plate and that removes heat from the electrode plate.

10. A plasma processing method for a plasma processing apparatus including a processing vessel, a mounting table on which a substrate is placed inside the processing vessel, and an upper electrode located at a position away from the mounting table, which performs plasma processing on the substrate inside the processing vessel by supplying high-frequency power to the upper electrode, the method comprising: (A) a step of supplying the high-frequency power to an electrode plate of the upper electrode and generating plasma inside the processing vessel via a dielectric plate of the upper electrode stacked on the electrode plate; and (B) during step (A), a step of cooling the electrode plate with a cooling mechanism connected to the electrode plate, and supplying a heat transfer gas to a heat transfer gas supply space formed between the electrode plate and the dielectric plate to cause the heat transfer gas to contain a viscous flow, thereby adjusting the thermal conductivity of the heat transfer gas.

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