Substrate processing method and substrate processing apparatus

Abstract

To increase the etching rate while suppressing the production of gaseous ruthenium tetroxide.SOLUTION: A substrate processing method includes a step of preparing a substrate having a ruthenium-containing layer on its surface (step S11), a step of bringing an alkaline etching solution into contact with the ruthenium-containing layer on the substrate (step S12), and a step of bringing the etching solution into contact with the ruthenium-containing layer in a state where plasma is applied to the etching solution to lower the pH (step 14) after the step S12. Thereby, the etching rate can be increased while suppressing the production of gaseous ruthenium tetroxide.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a technique for etching a ruthenium-containing layer on a substrate. [Background technology]

[0002] Conventionally, in the manufacturing process of semiconductor substrates (hereinafter simply referred to as "substrates"), various processes are performed on the substrate. For example, after forming a conductive film on the main surface of the substrate, a process is performed to remove the conductive film adhering to the bevel portion of the substrate. In recent years, with the miniaturization of devices on substrates, ruthenium (Ru) has attracted attention as a material for the conductive film. Ruthenium is difficult to remove by simply immersing it in an aqueous solution of an acid or alkali, such as hydrochloric acid or sodium hydroxide.

[0003] Therefore, Patent Document 1 proposes a ruthenium etching solution containing orthoperiodic acid and ammonia and having a pH of 4.5 (Table 1, Example A32) for etching ruthenium. Also, Patent Document 2 proposes a ruthenium etching solution containing orthoperiodic acid and ammonia and having a pH of 8 or more and 10 or less. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 138814 [Patent Document 2] Patent Publication No. 2021-90040 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when ruthenium is etched using the etching solution of Patent Document 1, there is a risk of generating toxic gaseous ruthenium tetroxide (RuO4). On the other hand, when ruthenium is etched using the etching solution of Patent Document 2, which has a relatively high pH, ​​there is a risk of the etching rate being low and the processing efficiency being reduced.

[0006] The present invention has been made in view of the above-mentioned problems, and has as its object to increase the etching rate while suppressing the generation of gaseous ruthenium tetroxide. [Means for solving the problem]

[0007] A first aspect of the present invention is a substrate processing method for etching a ruthenium-containing layer on a substrate, comprising: a) preparing a substrate having a ruthenium-containing layer on its surface; b) bringing an alkaline etching solution into contact with the ruthenium-containing layer on the substrate; and c) after step b), applying plasma to the etching solution to lower the pH, and then bringing the etching solution into contact with the ruthenium-containing layer.

[0008] A second aspect of the present invention is the substrate processing method of the first aspect, further comprising: d) after the step c), bringing the etching solution into contact with the ruthenium-containing layer while stopping application of plasma to the etching solution.

[0009] A third aspect of the present invention is the substrate processing method of the first or second aspect, wherein in the step b), ruthenium dioxide is produced from ruthenium in the ruthenium-containing layer, and in the step c), soluble ruthenium tetroxide is produced from the ruthenium dioxide.

[0010] A fourth aspect of the present invention is the substrate processing method of the first or second aspect (or any one of the first to third aspects), wherein the minimum pH value of the etching solution in the step c) is 7.0 or more and 7.5 or less.

[0011] A fifth aspect of the present invention is the substrate processing method of the first or second aspect (or any one of the first to fourth aspects), wherein the pH of the etching solution in the step b) is 8.0 or more and 10.0 or less.

[0012] A sixth aspect of the present invention is the substrate processing method of the first or second aspect (which may be any one of the first to fifth aspects), wherein the plasma is atmospheric plasma.

[0013] A seventh aspect of the present invention is the substrate processing method of the first or second aspect (which may be any one of the first to sixth aspects), wherein the plasma is room temperature plasma.

[0014] An eighth aspect of the present invention is the substrate processing method of the first or second aspect (or any one of the first to seventh aspects), wherein in the step c), steam is applied to and recovered from gaseous ruthenium tetroxide produced by contact of the ruthenium-containing layer with the etching solution.

[0015] A ninth aspect of the present invention is the substrate processing method of the first or second aspect (which may be any one of the first to eighth aspects), wherein in the steps b) and c), the etching solution contacts the ruthenium-containing layer at the peripheral portion of the substrate.

[0016] A tenth aspect of the present invention is the substrate processing method of the first or second aspect (which may be any one of the first to ninth aspects), wherein the etching solution contains orthoperiodic acid.

[0017] An eleventh aspect of the present invention is the substrate processing method of the tenth aspect, wherein the etching solution contains ammonia as an alkaline additive component.

[0018] A twelfth aspect of the present invention is a substrate processing apparatus for etching a ruthenium-containing layer on a substrate, comprising: a substrate holding unit for holding a substrate having a ruthenium-containing layer on its surface; a processing liquid supply unit for applying an alkaline etching liquid onto the substrate to bring it into contact with the ruthenium-containing layer; a plasma applying unit for applying plasma to the etching liquid; and a control unit for controlling the plasma applying unit after the alkaline etching liquid has come into contact with the ruthenium-containing layer, thereby bringing the etching liquid, the pH of which has been reduced by the application of plasma, into contact with the ruthenium-containing layer. [Effects of the Invention]

[0019] In the present invention, the etching rate can be increased while suppressing the generation of gaseous ruthenium tetroxide. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a plan view of a substrate processing system. [Figure 2] 1 is a side view of a substrate processing apparatus according to a first embodiment. [Figure 3] FIG. 2 is a diagram illustrating a configuration of a control unit. [Figure 4] FIG. 2 is an enlarged vertical cross-sectional view showing the vicinity of an etched portion. [Figure 5] FIG. 1 is a diagram showing a flow of substrate processing. [Figure 6] FIG. 10 is a graph showing changes in pH of an etching solution. [Figure 7] FIG. 10 is a diagram showing the state of etching of a ruthenium-containing layer using an etching solution of a comparative example. [Figure 8] FIG. 10 is a diagram showing the etching of a ruthenium-containing layer. [Figure 9] FIG. 10 is a side view of a substrate processing apparatus according to a second embodiment. [Figure 10] FIG. 1 is a diagram showing a part of a substrate processing flow. [Figure 11] FIG. 2 is an enlarged vertical cross-sectional view showing the vicinity of an etched portion. [Figure 12]FIG. 2 is an enlarged vertical cross-sectional view showing the vicinity of an etched portion. [Figure 13] FIG. 2 is a side view of the substrate processing apparatus. [Figure 14] FIG. 2 is a side view of the substrate processing apparatus. [Figure 15] FIG. 2 is a side view of the substrate processing apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0021] 1 is a schematic plan view showing the layout of a substrate processing system 10. The substrate processing system 10 is a system for processing semiconductor substrates 9 (hereinafter simply referred to as "substrates 9"). The substrate processing system 10 includes an indexer block 101 and a processing block 102 coupled to the indexer block 101.

[0022] The indexer block 101 includes a carrier holding unit 104, an indexer robot 105, and an IR movement mechanism 106. The carrier holding unit 104 holds a plurality of carriers 107, each capable of accommodating a plurality of substrates 9. The plurality of carriers 107 (e.g., FOUPs) are held by the carrier holding unit 104 while being arranged in a predetermined carrier arrangement direction. The IR movement mechanism 106 moves the indexer robot 105 in the carrier arrangement direction. The indexer robot 105 performs an unloading operation to unload the substrates 9 from the carriers 107, and a loading operation to load the substrates 9 into the carriers 107 held by the carrier holding unit 104. The substrates 9 are transported by the indexer robot 105 in a horizontal position.

[0023] The processing block 102 includes a plurality of (for example, four or more) processing units 108 that process substrates 9, and a center robot 109. The processing units 108 are arranged to surround the center robot 109 in a plan view. The processing units 108 perform various processes on the substrates 9. A substrate processing apparatus, which will be described later, is one of the processing units 108. The center robot 109 performs a loading operation to load the substrate 9 into the processing unit 108 and an unloading operation to unload the substrate 9 from the processing unit 108. Furthermore, the center robot 109 transports the substrate 9 between the plurality of processing units 108. The substrate 9 is transported in a horizontal position by the center robot 109. The center robot 109 receives the substrate 9 from the indexer robot 105 and passes the substrate 9 to the indexer robot 105.

[0024] 2 is a side view showing the configuration of a substrate processing apparatus 1 according to a first embodiment of the present invention. The substrate processing apparatus 1 is a single-wafer processing apparatus that processes substrates 9 one by one. The substrate processing apparatus 1 is an apparatus that performs wet etching on the peripheral portion of the substrate 9 (i.e., the bevel portion and the area near the bevel portion). FIG. 2 shows a cross section of part of the configuration of the substrate processing apparatus 1.

[0025] Substrate processing apparatus 1 includes substrate holding unit 31, substrate rotation mechanism 33, cup unit 4, supply head 5, etching unit 6, housing 11, and control unit 8. Substrate holding unit 31, substrate rotation mechanism 33, cup unit 4, etc. are housed in the internal space of housing 11. An airflow forming unit 12 is provided in the canopy of housing 11, supplying gas to the internal space to form a downward airflow (so-called downflow). An FFU (fan filter unit), for example, is used as airflow forming unit 12. Control unit 8 is disposed outside housing 11 and controls substrate holding unit 31, substrate rotation mechanism 33, supply head 5, etching unit 6, etc.

[0026] As shown in FIG. 3 , the control unit 8 is, for example, a typical computer system including a processor 81, a memory 82, an input / output unit 83, and a bus 84. The bus 84 is a signal circuit connecting the processor 81, the memory 82, and the input / output unit 83. The memory 82 stores programs and various information. The processor 81 executes various processes (e.g., numerical calculations) using the memory 82 and other components in accordance with the programs and other components stored in the memory 82. The input / output unit 83 includes a keyboard 85 and a mouse 86 for receiving input from an operator, a display 87 for displaying output and other components from the processor 81, and a transmitter for transmitting output and other components from the processor 81. The control unit 8 may be a programmable logic controller (PLC), a circuit board, or the like. The control unit 8 may include any two or more components of a computer system, a PLC, a circuit board, or the like.

[0027] The substrate holding unit 31 and substrate rotation mechanism 33 shown in Figure 2 are each part of a spin chuck that holds and rotates a substantially disk-shaped substrate 9. The substrate holding unit 31 holds the horizontally positioned substrate 9 from below. The substrate holding unit 31 is, for example, a vacuum chuck that holds the substrate 9 by suction. The substrate holding unit 31 has a substantially disk-shaped base unit 311 that comes into contact with and suctions the center of the lower main surface (hereinafter also referred to as the "lower surface 92") of the substrate 9. The diameter of the base unit 311 is smaller than the diameter of the substrate 9.

[0028] A ruthenium-containing layer 93 containing ruthenium (Ru) is present on the substrate 9. In the example shown in FIG. 2, the ruthenium-containing layer 93 is a film-like portion (i.e., a ruthenium-containing film) that covers the entire upper principal surface (hereinafter also referred to as the "upper surface 91") of the substrate 9. In FIG. 2, the ruthenium-containing layer 93 is indicated by a thick line. The ruthenium-containing layer 93 contains, for example, one or more of elemental ruthenium, a ruthenium alloy, a ruthenium oxide, a ruthenium nitride, or a ruthenium oxynitride. The ruthenium-containing layer 93 may be, for example, a film-like portion (i.e., a ruthenium-containing film) that covers the entire upper surface 91 and / or the lower surface 92 of the substrate 9, or may be a portion that covers only a portion of the surface of the substrate 9. In the present embodiment, the ruthenium-containing layer 93 is a ruthenium-containing film that covers the entire upper surface 91 of the substrate 9, and the peripheral edge of the substrate 9 is also covered by the ruthenium-containing film. In this embodiment, the ruthenium-containing layer 93 is a ruthenium film formed entirely of simple ruthenium. The substrate holder 31 shown in Fig. 2 holds the substrate 9 from below with the upper surface 91, on which the ruthenium-containing film is formed, facing upward.

[0029] The substrate rotation mechanism 33 is disposed below the substrate holding unit 31. The substrate rotation mechanism 33 rotates the substrate 9 together with the substrate holding unit 31 around a rotation axis J1 extending substantially parallel to the up-down direction. In the example shown in FIG. 2, the substrate rotation mechanism 33 rotates the substrate 9 clockwise in a plan view. The substrate rotation mechanism 33 includes a shaft 331 and a motor 332. The shaft 331 is a substantially columnar or cylindrical member centered on the rotation axis J1. The shaft 331 extends in the up-down direction and is connected to the center of the lower surface of the base unit 311 of the substrate holding unit 31. The motor 332 is an electric rotary motor that rotates the shaft 331. The substrate rotation mechanism 33 may be a motor having another structure (for example, a hollow motor, etc.). The rotation direction of the substrate 9 may also be counterclockwise.

[0030] The supply head 5 is disposed above the center of the substrate 9 in the radial direction (hereinafter simply referred to as the "radial direction") centered on the rotation axis J1. The supply head 5 faces the upper surface 91 of the substrate 9 in the vertical direction at a position spaced above the upper surface 91 of the substrate 9. The supply head 5 includes a lower head portion 51, an upper head portion 52, and a center nozzle 53. The lower head portion 51 is a substantially annular plate-shaped portion centered on the rotation axis J1. The lower surface of the lower head portion 51 is a substantially horizontal plane extending substantially parallel to the upper surface 91 of the substrate 9 and faces the upper surface 91 of the substrate 9 in the vertical direction. The diameter of the outer periphery of the lower head portion 51 in a plan view is smaller than the diameter of the substrate 9. The upper head portion 52 is a substantially cylindrical portion centered on the rotation axis J1 and extends upward from the upper surface of the lower head portion 51. The upper head portion 52 also serves as a support portion that supports the lower head portion 51 from above. The head upper portion 52 is supported by an arm (not shown) that extends substantially horizontally.

[0031] A pipe is provided inside the head upper part 52 to supply gas to the head lower part 51. The gas in question is, for example, compressed air or an inert gas such as nitrogen (N2) gas. In the following description, the gas in question is assumed to be an inert gas. The inert gas supplied to the head lower part 51 is sprayed from the lower surface and outer surface of the head lower part 51 toward the upper surface 91 of the substrate 9. This forms a stream of inert gas along the upper surface 91 of the substrate 9, flowing radially outward from the radial center of the substrate 9 (hereinafter simply referred to as the "center")

[0032] The center nozzle 53 is disposed in a through-hole provided in the center of the lower head portion 51. A processing liquid such as a rinse liquid is supplied to the center nozzle 53 via a pipe provided inside the upper head portion 52. The rinse liquid (e.g., deionized water (DIW)) supplied to the center nozzle 53 is ejected from the center nozzle 53 toward the center of the substrate 9 and spreads radially outward on the upper surface 91 of the substrate 9. Note that the rinse liquid is not limited to DIW and may be variously changed. Furthermore, various types of processing liquids other than the rinse liquid may be ejected from the center nozzle 53.

[0033] The cup unit 4 includes a cup 41 and a cup lifting mechanism (not shown). The cup 41 is an annular member centered on the rotation axis J1. The cup 41 is disposed around the substrate 9 and the substrate holding unit 31 over the entire circumference in the circumferential direction (hereinafter simply referred to as the "circumferential direction") centered on the rotation axis J1, and covers the sides and below of the substrate 9 and the substrate holding unit 31. The cup 41 is a liquid receiving container that receives liquid such as a processing liquid that splashes toward the surroundings from the rotating substrate 9. The inner surface of the cup 41 is formed, for example, from a water-repellent material. The cup 41 remains stationary in the circumferential direction regardless of whether the substrate 9 is rotating or stationary. A discharge port (not shown) is provided at the bottom of the cup 41 to discharge the processing liquid received in the cup 41 to the outside of the housing 11.

[0034] The cup lifting mechanism moves the cup 41 in the vertical direction relative to the substrate holder 31. The cup lifting mechanism includes, for example, an electric linear motor, an air cylinder, or a ball screw and an electric rotary motor connected to the cup 41. The cup lifting mechanism allows the cup 41 to move in the vertical direction between a processing position around the substrate 9 shown in FIG. 2 and a retracted position below the processing position.

[0035] The cup unit 4 may include a plurality of cups 41 stacked in the radial direction. When the cup unit 4 includes a plurality of cups 41, each of the plurality of cups 41 can be moved independently in the vertical direction, and the plurality of cups 41 can be switched to be used to receive the processing liquid depending on the type of processing liquid splashed from the substrate 9.

[0036] The etching unit 6 is disposed above the peripheral edge of the substrate 9. The etching unit 6 is disposed radially outward from the outer peripheral edge of the head lower part 51 of the supply head 5, and faces the ruthenium-containing layer 93 on the peripheral edge of the substrate 9 in the vertical direction. The etching unit 6 includes a treatment liquid supply unit 61 and a plasma application unit 62.

[0037] FIG. 4 is an enlarged longitudinal cross-sectional view showing the vicinity of the etching unit 6. In FIG. 4, the ruthenium-containing layer 93 (a ruthenium film in this embodiment) is indicated by a thick line. The processing liquid supply unit 61 includes a processing nozzle 611 that faces the upper surface 91 of the substrate 9 in the vertical direction near the peripheral edge of the substrate 9. The processing nozzle 611 is an insulating, substantially cylindrical member made of, for example, resin. The processing nozzle 611 is supported by an arm (not shown) and can be moved vertically and horizontally by an elevating mechanism and a moving mechanism connected to the arm. The elevating mechanism includes, for example, an electric linear motor, an air cylinder, or a ball screw and an electric rotary motor. The moving mechanism includes, for example, an electric rotary motor.

[0038] The processing nozzle 611 discharges processing liquid 71 for etching the ruthenium-containing layer 93 (i.e., etching liquid 71) toward the peripheral edge of the substrate 9. The processing nozzle 611 discharges the etching liquid 71 obliquely downward and radially outward from a discharge port provided at the lower end, for example. The etching liquid 71 applied from the processing nozzle 611 to the peripheral edge of the substrate 9 comes into contact with the ruthenium-containing layer 93 covering the substrate 9 at the peripheral edge, thereby etching the ruthenium-containing layer 93. The etching liquid 71 supplied from the processing nozzle 611 to the substrate 9 may wrap around from the upper surface 91 to the peripheral edge of the lower surface 92 of the substrate 9. When the etching liquid 71 is supplied from the processing nozzle 611 to the peripheral edge of the substrate 9, the above-mentioned inert gas is supplied from the supply head 5 (see FIG. 2) toward the substrate 9, forming a gas flow of the inert gas directed radially outward from the center of the substrate 9. This prevents the etching solution 71 from spreading to a region radially inward of the peripheral edge of the substrate 9.

[0039] The etching solution 71 contains orthoperiodic acid (H5IO6) as an oxidizing agent. The etching solution 71 also contains ammonia (NH3) as an alkaline additive. The etching solution 71 is, for example, an alkaline liquid in which orthoperiodic acid and ammonia are dissolved in water. In other words, the pH of the etching solution 71 is greater than 7.0. This pH is a value measured using a known pH meter under conditions of 23°C and 1 atmosphere. The same applies to the pH value in the following explanation.

[0040] The pH of the etching solution 71 is preferably 7.5 or higher, and more preferably 8.0 or higher. The pH of the etching solution 71 is preferably 10.0 or lower, and more preferably 9.0 or lower. The etching solution 71 may contain, for example, a pH adjuster for adjusting the pH in addition to orthoperiodic acid and ammonia.

[0041] The content of orthoperiodic acid in the etching solution 71 is, for example, 0.05% by mass to 8% by mass. The content of ammonia in the etching solution 71 is, for example, 5 parts by mass to 150 parts by mass per 100 parts by mass of orthoperiodic acid. The contents of orthoperiodic acid and ammonia in the etching solution 71 are not limited to the above ranges and may be changed in various ways. Furthermore, the etching solution 71 may contain an oxidizing agent other than orthoperiodic acid in addition to or instead of orthoperiodic acid. The etching solution 71 may contain an alkaline additive component other than ammonia in addition to or instead of ammonia.

[0042] The plasma applying unit 62 applies plasma to the etching solution 71. In the example shown in FIG. 4, the plasma applying unit 62 includes a plasma nozzle 621, a pair of plasma electrodes 622, and a power supply 623. The plasma nozzle 621 is supported above the peripheral edge of the substrate 9 by an arm (not shown), and can be moved up and down and horizontally by an elevating mechanism and a moving mechanism connected to the arm. The elevating mechanism includes, for example, an electric linear motor, an air cylinder, or a ball screw and an electric rotary motor. The moving mechanism includes, for example, an electric rotary motor.

[0043] The plasma nozzle 621 faces the upper surface 91 of the substrate 9 in the vertical direction near the peripheral edge of the substrate 9. The plasma nozzle 621 is an insulating, approximately cylindrical member made of, for example, resin. The plasma nozzle 621 is disposed radially outward of the processing nozzle 611 of the processing liquid supply unit 61. The plasma nozzle 621 is disposed, for example, on an extension of an imaginary straight line extending from the rotation axis J1 to the processing nozzle 611 in a plan view. The plasma nozzle 621 is supported with an outlet provided at its lower end facing the upper surface 91 of the substrate 9. The outlet of the plasma nozzle 621 is spaced above the upper surface 91 of the substrate 9.

[0044] The plasma nozzle 621 is connected to a gas supply source (not shown). The gas supplied from the gas supply source to the plasma nozzle 621 is delivered from the delivery port of the plasma nozzle 621 toward the peripheral edge of the substrate 9. The gas is, for example, a gas containing nitrogen, and in this embodiment, is the atmosphere (i.e., air). The gas may be various gases other than air (e.g., nitrogen gas).

[0045] A pair of plasma electrodes 622 are fixed to the outer surface of the plasma nozzle 621 at the bottom of the plasma nozzle 621 (i.e., near the outlet of the plasma nozzle 621). The pair of plasma electrodes 622 are arranged facing each other with the plasma nozzle 621 in between. The pair of plasma electrodes 622 are connected to a power supply 623, which is an AC power supply. The power supply 623 applies an AC voltage between the pair of plasma electrodes 622. This converts the gas flowing through the plasma nozzle 621 into plasma. Note that the power supply 623 is not limited to an AC power supply and may be, for example, a DC pulse power supply.

[0046] As described above, when the gas supplied from the gas supply source to the plasma nozzle 621 is air, atmospheric plasma is generated in the plasma nozzle 621. The plasma generated in the plasma nozzle 621 is, for example, room temperature plasma with a temperature of 40°C or less. The lower limit temperature of the room temperature plasma is not particularly limited, but is, for example, 5°C. Furthermore, the plasma is, for example, atmospheric pressure plasma generated under approximately atmospheric pressure (for example, 0.5 atm to 2.0 atm, preferably 0.75 atm to 1.5 atm).

[0047] The plasma generated by the plasma nozzle 621 is discharged from a discharge port at the tip of the plasma nozzle 621 and applied to the etching solution 71 supplied onto the substrate 9. The discharge port of the plasma nozzle 621 is preferably entirely immersed in the etching solution 71 supplied onto the substrate 9. This prevents the plasma (specifically, gas plasma) discharged from the discharge port of the plasma nozzle 621 from diffusing into the atmosphere surrounding the etching solution 71, and allows the plasma to be efficiently applied to the etching solution 71.

[0048] When plasma is applied to the etching solution 71 from the plasma nozzle 621, the pH of the etching solution 71 decreases. The pH of the etching solution 71 gradually decreases as the plasma application time increases. In the substrate processing apparatus 1, for example, the pH of the etching solution 71 decreases to a range of 7.0 or more and 7.5 or less. In other words, in the substrate processing apparatus 1, application of plasma to the alkaline etching solution 71 decreases the pH of the etching solution 71 within the alkaline range, or makes the etching solution 71 neutral. Note that application of plasma to the etching solution 71 may decrease the pH of the etching solution 71 to less than 7.0. In other words, the etching solution 71 may become acidic when plasma is applied. When application of plasma to the etching solution 71 is stopped, the pH of the etching solution 71 on the peripheral edge of the substrate 9 increases due to the mixing of the etching solution 71 newly supplied from the processing nozzle 611.

[0049] Next, the processing flow of the substrate 9 in the substrate processing apparatus 1 will be described with reference to FIG. 5. When the substrate 9 is processed, first, the substrate 9 is loaded into the substrate processing apparatus 1 and held substantially horizontally by the substrate holding unit 31 (step S11). This prepares the substrate 9 having a ruthenium-containing layer 93 (a ruthenium film in this embodiment) on its surface. In step S11, the position of the substrate holding unit 31 is adjusted so that the center of the substrate 9 coincides with the rotation axis J1 in a plan view. When the substrate 9 is loaded, the supply head 5 and the etching unit 6 are retracted to retracted positions (for example, positions spaced radially outward from the outer periphery of the substrate 9 in a plan view) that do not interfere with the loading and unloading of the substrate 9. Once the substrate 9 is held by the substrate holding unit 31, the control unit 8 controls the substrate rotation mechanism 33 to start rotating the substrate 9. The supply head 5 and the etching unit 6 are then moved from the retracted positions to the processing positions shown in FIG. 2.

[0050] Subsequently, the control unit 8 controls the processing liquid supply unit 61, whereby the alkaline etching liquid 71 is discharged from the processing nozzle 611 toward the peripheral edge of the substrate 9, and the etching liquid 71 comes into contact with the ruthenium-containing layer 93 on the peripheral edge (step S12). As a result, the ruthenium-containing layer 93 on the peripheral edge of the substrate 9 is etched. The pH of the etching liquid 71 in step S12 is, for example, 8.0 or more and 10.0 or less.

[0051] In step S12, no plasma is applied to the etching solution 71 supplied to the ruthenium-containing layer 93. In step S12, the control unit 8 controls the supply head 5, thereby supplying an inert gas from the head lower portion 51 toward the substrate 9, and forming an inert gas flow that flows radially outward from the center of the substrate 9. This prevents the etching solution 71 from spreading radially inward beyond the peripheral edge of the substrate 9. The supply of the etching solution 71 from the processing liquid supply unit 61 and the supply of the inert gas from the supply head 5 are continued until step S17, which will be described later.

[0052] After a predetermined time has elapsed since the start of discharge of the etching solution 71, the control unit 8 controls the plasma applying unit 62 to supply gas (air in this embodiment) to the plasma nozzle 621 and apply a voltage between the pair of plasma electrodes 622. This converts the gas flowing through the plasma nozzle 621 into plasma, and application of plasma to the etching solution 71 on the peripheral edge of the substrate 9 begins (step S13). On the peripheral edge of the substrate 9, the pH of the etching solution 71 gradually decreases due to the application of plasma. Then, by bringing the etching solution 71 with a reduced pH into contact with the ruthenium-containing layer 93, etching of the ruthenium-containing layer 93 further progresses (step S14). The minimum pH of the etching solution 71 in step S14 is, for example, 7.0 or higher and 7.5 or lower.

[0053] FIG. 6 is a graph schematically illustrating a change in pH of the etching solution 71 that contacts the ruthenium-containing layer 93 during processing of the substrate 9 in the substrate processing apparatus 1. The horizontal axis in FIG. 6 represents the elapsed time from the start of application of the etching solution 71 to the substrate 9, and the vertical axis represents the pH of the etching solution 71 that contacts the ruthenium-containing layer 93 on the peripheral portion of the substrate 9. In the example illustrated in FIG. 6, the pH of the etching solution 71 is 8.0 in step S12 (i.e., before plasma application), begins to decrease in step S13, and decreases to 7.0 in step S14. Note that, although the example illustrated in FIG. 6 depicts the change in pH of the etching solution 71 linearly, this is not a limitation. Furthermore, in step S14, the pH of the etching solution 71 is maintained at a minimum value of 7.0 for a certain period of time, but maintaining the pH at this minimum value is not necessarily required. Furthermore, the pH of the etching solution 71 in step S12 and the minimum pH of the etching solution 71 in step S14 may be changed as appropriate.

[0054] After a predetermined time has elapsed since the start of plasma application, the control unit 8 controls the plasma application unit 62 to stop the supply of gas to the plasma nozzle 621 and the application of voltage to the pair of plasma electrodes 622, thereby stopping the application of plasma to the etching solution 71 (step S15). As a result, as shown in FIG. 6, the pH of the etching solution 71 in contact with the ruthenium-containing layer 93 on the peripheral edge of the substrate 9 begins to increase. Then, with the application of plasma to the etching solution 71 stopped, the etching solution 71 is brought into contact with the ruthenium-containing layer 93, thereby further etching the ruthenium-containing layer 93 (step S16). In the example shown in FIG. 6, in step S16, the pH of the etching solution 71 returns to 8.0, as in step S12, and is maintained at 8.0.

[0055] When a predetermined time has elapsed since the application of plasma was stopped, the control unit 8 controls the processing liquid supply unit 61 to stop the supply of the etching liquid 71 to the substrate 9 (step S17). The supply of the inert gas from the supply head 5 is also stopped. The etching unit 6 moves from the processing position shown in FIG. 4 to the retreat position described above.

[0056] Next, a rinse liquid is supplied from the center nozzle 53 of the supply head 5 (see FIG. 2) to the center of the upper surface 91 of the substrate 9. The rotation speed of the substrate 9 by the substrate rotation mechanism 33 is also increased. This causes the rinse liquid to spread over the entire upper surface 91 of the substrate 9, and a rinse process is performed in which the etching liquid 71 and the like adhering to the peripheral edge of the substrate 9 are washed away (step S18). The rinse liquid is scattered radially outward from the outer periphery of the substrate 9 by the centrifugal force generated by the rotation of the substrate 9, and is received by the cup portion 4.

[0057] After the rinsing process on the substrate 9 has been performed for a predetermined time, the supply of the rinsing liquid from the center nozzle 53 is stopped. Thereafter, the rotation speed of the substrate 9 is further increased, and the rinsing liquid on the substrate 9 is shaken off and removed, thereby drying the substrate 9 (step S19). After the drying process on the substrate 9 is completed, the rotation of the substrate 9 is stopped, and the substrate 9 is unloaded from the substrate processing apparatus 1. The rinsing process and drying process on the substrate 9 may be performed by a method different from the above example.

[0058] In the substrate processing apparatus 1, as described above, the ruthenium-containing layer 93 is etched in step S14 using the etching solution 71 having a relatively low pH (for example, 7.0 to 7.5), thereby increasing the etching rate and improving the etching processing efficiency. Furthermore, by making the etching solution 71 alkaline (for example, pH 8.0 to 10.0) at the start of etching, it is possible to suppress the generation of toxic gaseous ruthenium tetroxide (RuO4) during etching. The principle of suppressing the generation of ruthenium tetroxide will be described below.

[0059] Suppose a ruthenium etching solution containing orthoperiodic acid and ammonia and having a pH of 4.5 (hereinafter also referred to as "comparative etching solution 701") is applied to the peripheral edge of a ruthenium-containing layer 93 on a substrate 9, then, as shown in Fig. 7, the ruthenium contained in the ruthenium-containing layer 93 is oxidized by the comparative etching solution 701, and highly volatile, water-insoluble ruthenium tetroxide 94 is generated. The toxic gaseous ruthenium tetroxide 94 then diffuses into the atmosphere surrounding the comparative etching solution 701.

[0060] Meanwhile, in the substrate processing apparatus 1, in step S12, an alkaline etching solution 71 before plasma application is applied to the ruthenium-containing layer 93 on the substrate 9, whereby the ruthenium contained in the ruthenium-containing layer 93 (i.e., metallic ruthenium) is oxidized by the etching solution 71 to produce ruthenium dioxide (RuO2) 95, as shown in Fig. 8. Then, in step S14, the etching solution 71, whose pH has been reduced after plasma application, is applied to the ruthenium dioxide 95, whereby the ruthenium dioxide 95 is oxidized to produce water-soluble ruthenium tetroxide 96. The water-soluble ruthenium tetroxide 96 dissolves in the etching solution 71, thereby preventing the diffusion of toxic gaseous ruthenium tetroxide into the atmosphere surrounding the etching solution 71.

[0061] Next, a substrate processing apparatus 1a according to a second embodiment of the present invention will be described. FIG. 9 is a side view showing the substrate processing apparatus 1a. In the substrate processing apparatus 1a, the processing nozzle 611 shown in FIG. 2 is omitted, and instead, etching solution 71 is discharged toward the center of a substrate 9 from a center nozzle 53 of a supply head 5. In other words, in an etching unit 6a of the substrate processing apparatus 1a, a processing solution supply unit 61a includes a center nozzle 53 as a processing nozzle. In the etching unit 6a, a plasma application unit 62a includes a plurality of plasma nozzles 621 as described above. The plurality of plasma nozzles 621 are arranged in the circumferential direction along the peripheral edge of the substrate 9 above an upper surface 91 of the substrate 9. The other components of the substrate processing apparatus 1a are substantially the same as those of the substrate processing apparatus 1, and the same reference numerals will be used in the following description.

[0062] In the substrate processing apparatus 1a, a protective film 97 is provided on a ruthenium-containing layer 93 that covers the entire upper surface 91 of the substrate 9. The protective film 97 is, for example, a spin-on-glass (SOG) film, and is provided on the entire upper surface 91 of the substrate 9 except for the peripheral edge portion. The protective film 97 has a substantially circular shape in a plan view.

[0063] The processing flow for substrate 9 in substrate processing apparatus 1a is substantially the same as that shown in Fig. 5, except that steps S21 and S22 shown in Fig. 10 are performed between the above-mentioned rinsing process (step S18) and drying process (step S19). Specifically, first, substrate 9 having ruthenium-containing layer 93 and protective film 97 provided thereon is prepared by being held by substrate holder 31 (Fig. 5: step S11). Then, substrate rotation mechanism 33 starts to rotate substrate 9.

[0064] Next, control unit 8 controls processing liquid supply unit 61a, and alkaline etching liquid 71 is discharged from center nozzle 53 toward the center of substrate 9. Centrifugal force generated by the rotation of substrate 9 causes etching liquid 71 to spread radially outward over protective film 97. Etching liquid 71 contacts the ruthenium-containing layer 93 exposed from protective film 97 at the peripheral edge of substrate 9 (step S12). This etches the ruthenium-containing layer 93 at the peripheral edge of substrate 9. The pH of etching liquid 71 in step S12 is, for example, 8.0 or more and 10.0 or less. In step S12 and steps S13 to S16 (described later), the region of ruthenium-containing layer 93 covered with protective film 97 is not etched. Furthermore, no inert gas is supplied from supply head 5.

[0065] After a predetermined time has elapsed since the start of the discharge of the etching solution 71, the control unit 8 controls the plasma application unit 62 to supply gas (air in this embodiment) to each plasma nozzle 621 and apply a voltage between a pair of plasma electrodes 622 (see FIG. 4) fixed to each plasma nozzle 621. This converts the gas flowing through each plasma nozzle 621 into plasma, and application of plasma to the etching solution 71 on the peripheral edge of the substrate 9 begins (step S13). On the peripheral edge of the substrate 9, the pH of the etching solution 71 gradually decreases due to the application of plasma. Then, by bringing the etching solution 71 with a reduced pH into contact with the ruthenium-containing layer 93, etching of the ruthenium-containing layer 93 further progresses (step S14). The minimum pH of the etching solution 71 in step S14 is, for example, 7.0 or higher and 7.5 or lower.

[0066] After a predetermined time has elapsed since the start of plasma application, the control unit 8 controls the plasma application unit 62 to stop the supply of gas to each plasma nozzle 621 and the application of voltage to the pair of plasma electrodes 622 fixed to each plasma nozzle 621, thereby stopping the application of plasma to the etching solution 71 (step S15). As a result, the pH of the etching solution 71 in contact with the ruthenium-containing layer 93 on the peripheral edge of the substrate 9 begins to increase. Then, with the application of plasma to the etching solution 71 stopped, the etching of the ruthenium-containing layer 93 is further progressed by bringing the etching solution 71 into contact with the ruthenium-containing layer 93 (step S16). The pH of the etching solution 71 in contact with the ruthenium-containing layer 93 returns to the same value as the pH in step S12.

[0067] When a predetermined time has elapsed since the application of plasma was stopped, the control unit 8 controls the processing liquid supply unit 61a to stop the supply of the etching liquid 71 to the substrate 9 (step S17). Note that in the above steps S12 to S16, a puddle process may be performed in which a liquid film of the etching liquid 71 is formed and maintained on the upper surface 91 of the substrate 9 while the rotation of the substrate 9 is stopped or while the substrate 9 is being rotated at a low speed.

[0068] Next, a rinse liquid is supplied from the center nozzle 53 of the supply head 5 to the central portion of the upper surface 91 of the substrate 9. Furthermore, the rotation speed of the substrate 9 by the substrate rotation mechanism 33 is increased. As a result, the rinse liquid spreads over the entire upper surface 91 of the substrate 9, and a rinse process is performed in which the etching liquid 71 and the like adhering to the peripheral portion of the substrate 9 are washed away (step S18). The rinse liquid is scattered radially outward from the outer peripheral edge of the substrate 9 by the centrifugal force generated by the rotation of the substrate 9, and is received by the cup portion 4.

[0069] After the rinsing process on the substrate 9 has been performed for a predetermined time, the supply of the rinsing liquid to the substrate 9 is stopped, and the protective film 97 is removed from the substrate 9 (FIG. 10: step S21). As described above, if the protective film 97 is an SOG film, in step S21, for example, the protective film 97 is removed by applying hydrogen fluoride (HF) to the protective film 97. Note that the type of protective film 97 and the method for removing the protective film 97 may be changed in various ways.

[0070] After the removal of the protective film 97 is completed, a rinse liquid is supplied from the center nozzle 53 to the center of the upper surface 91 of the substrate 9, and the substrate 9 is rinsed (step S22). Thereafter, the rotation speed of the substrate 9 is increased, and the rinse liquid on the substrate 9 is shaken off and removed, thereby drying the substrate 9 (step S19). After the drying process of the substrate 9 is completed, the rotation of the substrate 9 is stopped, and the substrate 9 is unloaded from the substrate processing apparatus 1a.

[0071] As described above, the substrate processing methods according to the first and second embodiments include the steps of preparing substrate 9 having ruthenium-containing layer 93 on its surface (step S11), bringing alkaline etching solution 71 into contact with ruthenium-containing layer 93 on substrate 9 (step S12), and, after step S12, applying plasma to etching solution 71 to lower the pH and then bringing etching solution 71 into contact with ruthenium-containing layer 93 (step S14). This makes it possible to increase the etching rate while suppressing the generation of toxic gaseous ruthenium tetroxide, as described above.

[0072] Preferably, the substrate processing method further includes, after step S14, a step (step S16) of bringing etching solution 71 into contact with ruthenium-containing layer 93 while stopping the application of plasma to etching solution 71. This shortens the time during which etching solution 71, which has a relatively low pH (for example, pH 7.0 to 7.5), contacts ruthenium-containing layer 93, out of the total contact time between etching solution 71 and ruthenium-containing layer 93. As a result, it is possible to suitably suppress the generation of ruthenium tetroxide in a toxic gaseous state.

[0073] In the above substrate processing method, it is preferable that ruthenium dioxide is generated from the ruthenium in the ruthenium-containing layer 93 in step S12, and soluble ruthenium tetroxide is generated from the ruthenium dioxide in step S14. This makes it possible to suitably suppress the generation of gaseous ruthenium tetroxide, as described above.

[0074] In the substrate processing method, the minimum pH value of etching solution 71 in step S14 is preferably 7.0 or more and 7.5 or less, which makes it possible to preferably suppress the generation of gaseous ruthenium tetroxide and increase the etching rate at the same time.

[0075] In the substrate processing method, the pH of etching solution 71 in step S12 is preferably 8.0 or more and 10.0 or less, which makes it possible to preferably suppress the generation of gaseous ruthenium tetroxide and increase the etching rate at the same time.

[0076] In the substrate processing method, the plasma is preferably atmospheric plasma, which simplifies the configuration for generating the plasma.

[0077] In the substrate processing method, the plasma is preferably room temperature plasma. This simplifies the configuration for generating the plasma. Furthermore, since ruthenium tetroxide becomes relatively volatile at temperatures above 45°C, the generation of gaseous ruthenium tetroxide can be suitably suppressed by setting the plasma temperature to 40°C or less.

[0078] In the above substrate processing method, in steps S12 and S14, the etching solution 71 preferably contacts the ruthenium-containing layer 93 at the peripheral edge of the substrate 9. This allows the ruthenium-containing layer 93 at the peripheral edge of the substrate 9 to be suitably etched.

[0079] As described above, the etching solution 71 preferably contains orthoperiodic acid, which allows the ruthenium contained in the ruthenium-containing layer 93 to be suitably etched.

[0080] As described above, it is preferable that the etching solution 71 contains ammonia as an alkaline additive component, which makes it possible to easily prepare an alkaline etching solution 71 suitable for etching ruthenium.

[0081] The substrate processing apparatus 1, 1a described above includes a substrate holding unit 31, a processing liquid supply unit 61, 61a, a plasma applying unit 62, and a control unit 8. The substrate holding unit 31 holds a substrate 9 having a ruthenium-containing layer 93 on its surface. The processing liquid supply unit 61, 61a applies an alkaline etching liquid 71 onto the substrate 9 to bring it into contact with the ruthenium-containing layer 93. The plasma applying unit 62 applies plasma to the etching liquid 71. After the alkaline etching liquid 71 comes into contact with the ruthenium-containing layer 93, the control unit 8 controls the plasma applying unit 62 to bring the etching liquid 71, the pH of which has been reduced by the application of plasma, into contact with the ruthenium-containing layer 93. As described above, the substrate processing apparatus 1, 1a can increase the etching rate while suppressing the generation of toxic gaseous ruthenium tetroxide.

[0082] In the substrate processing apparatus 1 described above, the structure of the etching unit 6 is not limited to the example shown in Fig. 4 and may be modified in various ways. For example, in the etching unit 6b shown in Fig. 11, the tip of the plasma nozzle 621 of the plasma applying unit 62 is connected to a pipe 612 inside the processing nozzle 611 of the processing liquid supply unit 61. Furthermore, the pair of plasma electrodes 622 of the plasma applying unit 62 are fixed to the outer surface of the plasma nozzle 621 outside the processing nozzle 611. The pair of plasma electrodes 622 are disposed, for example, near the connection between the plasma nozzle 621 and the processing nozzle 611.

[0083] In the etching unit 6b, when a voltage is applied between the pair of plasma electrodes 622 from the power supply 623 in the above-described step S13, the gas (e.g., air) flowing in the plasma nozzle 621 is converted into plasma, and the plasma is applied to the etching solution flowing in the piping 612 of the processing nozzle 611. This decreases the pH of the etching solution flowing in the piping 612 of the processing nozzle 611. Note that in the etching unit 6b, a porous member may be provided in the piping 612 of the processing nozzle 611 at a connection portion with the plasma nozzle 621. This improves the uniformity of application of plasma to the etching solution flowing in the piping 612 of the processing nozzle 611.

[0084] 12, the tip of a plasma nozzle 621 of a plasma applying unit 62 is connected to a pipe 612 inside a processing nozzle 611 of a processing liquid supply unit 61. A pair of plasma electrodes 622 of the plasma applying unit 62 is fixed to the outer surface of the pipe 612 inside the processing nozzle 611. The pair of plasma electrodes 622 is disposed, for example, near a connection between the plasma nozzle 621 and the pipe 612 of the processing nozzle 611. The pair of plasma electrodes 622 is disposed between the connection and a discharge port provided at the lower end of the processing nozzle 611.

[0085] In the etching unit 6c, a gas (e.g., air) flowing through the plasma nozzle 621 is supplied to the etching liquid flowing through the pipe 612 of the processing nozzle 611, and flows as bubbles in the etching liquid toward the outlet of the processing nozzle 611 together with the etching liquid. In step S13 described above, when a voltage is applied between the pair of plasma electrodes 622 from the power supply 623, the bubbles in the etching liquid flowing through the pipe 612 of the processing nozzle 611 are converted into plasma. In other words, plasma is imparted to the etching liquid flowing through the pipe 612 of the processing nozzle 611. As a result, the pH of the etching liquid flowing through the pipe 612 of the processing nozzle 611 decreases.

[0086] The structure of the etching units 6b and 6c described above may be applied to the substrate processing apparatus 1a shown in Fig. 9. In this case, a plasma nozzle 621 is connected to the center nozzle 53 instead of the processing nozzle 611 in Figs.

[0087] As described above, the substrate processing apparatus 1a can prevent gaseous ruthenium tetroxide from diffusing into the atmosphere surrounding the etching solution 71. However, there is a possibility that a small amount of toxic gaseous ruthenium tetroxide may be generated, for example, in step S14. For this reason, the substrate processing apparatus 1a may be provided with a gas recovery unit 66 that recovers gaseous ruthenium tetroxide, as shown in FIG. 13, in preparation for the generation of gaseous ruthenium tetroxide.

[0088] The gas recovery unit 66 includes a recovery head 661, a recovery chamber 662, and a steam nozzle 663. The recovery head 661 is disposed above the peripheral edge of the substrate 9 and sucks in the atmosphere above the peripheral edge of the substrate 9. The recovery head 661 has, for example, a substantially annular shape in plan view centered on the rotation axis J1 and includes a plurality of suction ports arranged circumferentially on its underside. The atmosphere sucked in by the recovery head 661 is sent to the internal space of a recovery chamber 662 disposed outside the housing 11. Steam (i.e., moist air containing water vapor) is supplied from the steam nozzle 663 to the internal space of the recovery chamber 662. The temperature of the steam is, for example, 40°C to 90°C. In the recovery chamber 662, if the atmosphere recovered by the recovery head 661 contains gaseous ruthenium tetroxide, the ruthenium tetroxide reacts with the water vapor in the steam to generate H2RuO5, and the H2RuO5 is recovered.

[0089] 13 , in step S14, steam is applied to and recovered from gaseous ruthenium tetroxide generated by contact between the ruthenium-containing layer 93 and the etching solution 71. This makes it possible to prevent the gaseous ruthenium tetroxide from diffusing into the atmosphere within the housing 11. It is also possible to prevent the gaseous ruthenium tetroxide from reacting with ruthenium in the ruthenium-containing layer 93 on the substrate 9 and being reduced to ruthenium dioxide. In the gas recovery unit 66, in addition to the atmosphere recovered by the recovery head 661, the atmosphere discharged to the outside of the housing 11 from the discharge port of the cup unit 4 may also be sent to the recovery chamber 662.

[0090] The structure of the gas recovery unit 66 is not limited to the example shown in FIG. 13 and may be modified in various ways. For example, a gas recovery unit 66d shown in FIG. 14 includes a recovery cover 664d and a steam nozzle 663d. The recovery cover 664d is, for example, a covered, substantially cylindrical member. The recovery cover 664d covers the upper and surrounding areas of the substrate 9 inside the housing 11. In the example shown in FIG. 14, the base portion 311d of the substrate holding unit 31 extends around the entire circumference, radially outward beyond the periphery of the substrate 9, and the lower end of the recovery cover 664d is in airtight contact with the upper surface of the base portion 311d.

[0091] The steam nozzle 663d supplies steam to the internal space of the recovery cover 664d (i.e., the space surrounded by the recovery cover 664d and the base portion 311d). As a result, if gaseous ruthenium tetroxide is generated during etching of the ruthenium-containing layer 93, the ruthenium tetroxide reacts with water vapor in the steam to generate H2RuO5. The H2RuO5 is discharged to the outside of the recovery cover 664d through a discharge port (not shown) provided in the recovery cover 664d, and is sent to the outside of the housing 11 and recovered.

[0092] In this case as well, in step S14, by adding steam to the gaseous ruthenium tetroxide generated by contact between the ruthenium-containing layer 93 and the etching solution 71 and recovering it, it is possible to prevent the gaseous ruthenium tetroxide from diffusing into the atmosphere within the housing 11.

[0093] 15 includes a plurality of steam nozzles 663e. The tip of each steam nozzle 663e is inserted into the liquid film of etching liquid 71 supplied onto substrate 9, and steam is supplied into etching liquid 71 from the outlet at the tip. As a result, if gaseous ruthenium tetroxide is generated during etching of ruthenium-containing layer 93, the ruthenium tetroxide reacts with water vapor in the steam in the liquid film of etching liquid 71 to generate H2RuO5. The H2RuO5 is discharged together with etching liquid 71 to the outside of housing 11 via an exhaust port (not shown) of cup portion 4 and recovered.

[0094] In this case as well, in step S14, by adding steam to the gaseous ruthenium tetroxide generated by contact between the ruthenium-containing layer 93 and the etching solution 71 and recovering it, it is possible to prevent the gaseous ruthenium tetroxide from diffusing into the atmosphere within the housing 11.

[0095] The substrate processing apparatus 1 shown in FIG. 2 may also be provided with the gas recovery units 66, 66d, and 66e, as in the substrate processing apparatus 1a.

[0096] The above-described substrate processing apparatus 1, 1a and substrate processing method can be modified in various ways.

[0097] For example, the processing liquid supply unit 61 of the substrate processing apparatus 1 may further include, in addition to the above-mentioned processing nozzle 611, another processing nozzle that is arranged below the substrate 9 and ejects the etching liquid 71 toward the peripheral portion of the lower surface 92 of the substrate 9. The same applies to the substrate processing apparatus 1a.

[0098] The substrate processing apparatus 1 may be provided with a heater that heats the etching solution 71 supplied to the peripheral edge portion of the substrate 9. The heater may be, for example, an electric heater that is disposed below the peripheral edge portion of the substrate 9 and faces the lower surface 92 of the substrate 9. The same applies to the substrate processing apparatus 1a.

[0099] In the substrate processing apparatus 1, the plasma applied from the plasma application unit 62 does not necessarily have to be room temperature plasma of 40°C or less, and the temperature of the plasma may be higher than 40°C. Furthermore, the plasma does not necessarily have to be atmospheric pressure plasma, and may be, for example, low pressure plasma. The method of applying plasma to the etching solution 71 is not limited to the above example and may be variously modified. The same applies to the substrate processing apparatus 1a.

[0100] In the above-described substrate processing method, step S16 may be omitted, and the stopping of the application of plasma to the etching solution 71 (step S15) and the stopping of the supply of the etching solution 71 to the substrate 9 (step S17) may be performed approximately simultaneously.

[0101] The substrate holder 31 may hold the substrate 9 with the main surface of the substrate 9 on which the ruthenium-containing layer 93 is provided facing downward.

[0102] The substrate processing apparatus 1 may be provided with a plurality of etching units 6, which may be arranged in the circumferential direction along the peripheral edge of the substrate 9.

[0103] In the substrate processing apparatus 1a, an arm (not shown) supporting the center nozzle 53 may be swung approximately horizontally above the rotating substrate 9, thereby supplying the etching liquid 71 over approximately the entire upper surface 91 of the substrate 9. In other words, the etching liquid 71 may be supplied to the upper surface 91 of the substrate 9 from a so-called scan nozzle. In this case, by stopping the scan nozzle above the peripheral edge of the substrate 9, the etching liquid 71 can also be supplied only to the peripheral edge of the rotating substrate 9.

[0104] The above-described substrate processing method may be applied to a process other than etching the peripheral portion of the substrate 9. For example, in the substrate processing apparatus 1a, a substrate 9 not provided with a protective film 97 may be processed to form a ruthenium-containing wiring in a region radially inward from the peripheral portion of the substrate 9. In this case, the plasma applying unit 62 that applies plasma to the etching solution 71 discharged from the center nozzle 53 is disposed above the center of the substrate 9, for example.

[0105] The above-described substrate processing apparatus 1, 1a may be used to process glass substrates used in flat panel displays such as liquid crystal displays or organic EL (Electro Luminescence) displays, or glass substrates used in other displays, in addition to semiconductor substrates. The above-described substrate processing apparatus 1, 1a may also be used to process substrates for optical disks, magnetic disks, magneto-optical disks, photomasks, ceramic substrates, solar cell substrates, etc.

[0106] The configurations of the above-described embodiment and each modification may be combined as appropriate as long as they are not mutually contradictory. [Explanation of symbols]

[0107] 1, 1a Substrate processing equipment 8 Control Unit 9 Substrate 31 Board holding part 61 Processing liquid supply unit 62 Plasma application unit 71 Etching solution 93 Ruthenium-containing layer J1 rotation axis

Claims

1. 1. A substrate processing method for performing an etching process on a ruthenium-containing layer on a substrate, comprising: a) providing a substrate having a ruthenium-containing layer thereon; b) contacting the ruthenium-containing layer on the substrate with an alkaline etching solution; c) after step b), applying plasma to the etching solution to lower the pH, and then contacting the etching solution with the ruthenium-containing layer; A substrate processing method comprising:

2. 2. The substrate processing method according to claim 1, d) after the step c), bringing the etching solution into contact with the ruthenium-containing layer while stopping application of plasma to the etching solution.

3. 3. The substrate processing method according to claim 1, further comprising: In the step b), ruthenium dioxide is produced from ruthenium in the ruthenium-containing layer, A substrate processing method, wherein in the step c), soluble ruthenium tetroxide is produced from the ruthenium dioxide.

4. 3. The substrate processing method according to claim 1, further comprising: The substrate processing method, wherein the minimum pH value of the etching solution in the step c) is 7.0 or more and 7.5 or less.

5. 3. The substrate processing method according to claim 1, further comprising: The substrate processing method, wherein the pH of the etching solution in the step b) is 8.0 or more and 10.0 or less.

6. 3. The substrate processing method according to claim 1, further comprising: The substrate processing method, wherein the plasma is atmospheric plasma.

7. 3. The substrate processing method according to claim 1, further comprising: The substrate processing method is characterized in that the plasma is room temperature plasma.

8. 3. The substrate processing method according to claim 1, further comprising: a step of applying steam to gaseous ruthenium tetroxide produced by contact of the ruthenium-containing layer with the etching solution, and recovering the gaseous ruthenium tetroxide;

9. 3. The substrate processing method according to claim 1, further comprising: In the steps b) and c), the etching solution contacts the ruthenium-containing layer at the peripheral edge of the substrate.

10. 3. The substrate processing method according to claim 1, further comprising:

4. A substrate processing method, wherein the etching solution contains orthoperiodic acid.

11. 11. The substrate processing method according to claim 10, 4. A substrate processing method, wherein the etching solution contains ammonia as an alkaline additive component.

12. 1. A substrate processing apparatus for performing an etching process on a ruthenium-containing layer on a substrate, comprising: a substrate holder for holding a substrate having a ruthenium-containing layer on its surface; a treatment liquid supply unit that applies an alkaline etching liquid onto the substrate to bring the alkaline etching liquid into contact with the ruthenium-containing layer; a plasma applying unit that applies plasma to the etching solution; a control unit that controls the plasma applying unit after the alkaline etching solution has been brought into contact with the ruthenium-containing layer, thereby bringing the etching solution, the pH of which has been reduced by the application of plasma, into contact with the ruthenium-containing layer; A substrate processing apparatus comprising:

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