Substrate processing method and substrate processing device

Abstract

This substrate processing method comprises: a step for supplying a conductive processing liquid for etching to a substrate (9) on which a film (96) to be processed is positioned in a recess (95) of a pattern, and bringing the processing liquid into contact with the film (96) to be processed; and a step for repeatedly switching an application voltage applied between the substrate (9) and the processing liquid between a first voltage and a second voltage different from each other in a predetermined switching cycle in a state where the processing liquid is in contact with the film (96) to be processed, thereby repeatedly switching the potential of a side wall surface (942) forming the recess (95) between a first potential and a second potential smaller than the first potential. The first potential is 0 V or more, and the second potential is 0 V or less. Furthermore, the switching period is 0.05 seconds or more. Thus, the etching rate of the film (96) to be processed can be increased.

Description

Substrate processing method and substrate processing apparatus

[0001] The present invention relates to a technique for etching a substrate. [Reference to Related Applications] This application claims the benefit of priority from Japanese Patent Application JP2024-35790 filed on March 8, 2024, and Japanese Patent Application JP2025-14490 filed on January 31, 2025, the entire disclosures of which are incorporated herein by reference.

[0002] Conventionally, in the manufacturing process of semiconductor substrates (hereinafter simply referred to as "substrates"), various processes are performed on the substrates. For example, in the manufacturing process of substrates, a wet etching process is performed in which an etching solution is applied to the substrate to remove a film on the substrate. It is known that the wet etching process reduces the etching rate of a film in minute recesses such as trenches and holes provided on the substrate.

[0003] Therefore, Japanese Patent Laid-Open No. 2020-155614 (Document 1) proposes a technique in which a conductive etching solution is supplied onto a substrate and a constant DC current is applied between the processing solution adhering to the substrate and the substrate, thereby rapidly infiltrating the conductive components of the processing solution into the gaps of the microstructure. Also, International Publication No. 2021 / 192502 (Document 2) proposes a technique for increasing the etching rate by applying an AC voltage of 0.1 kHz or 1 kHz to a pair of electrodes arranged to sandwich a substrate in contact with the etching solution.

[0004] Meanwhile, there is a demand for a further increase in the etching rate in the etching process of a substrate, particularly for etching a film in a minute recess, where the etching rate is significantly reduced by a conventional etching method.

[0005] The present invention is directed to a technique for etching a substrate, and aims to increase the etching rate.

[0006] A first aspect of the present invention is a substrate processing method for etching a substrate having a target film located in a recess of a pattern, the method comprising the steps of: (a) supplying a conductive etching treatment liquid to the substrate and bringing it into contact with the target film; and (b) repeatedly switching an applied voltage between the substrate and the treatment liquid, while the treatment liquid is in contact with the target film, between a first voltage and a second voltage that are different from each other, at a predetermined switching period, thereby repeatedly switching a potential of a sidewall surface forming the recess between a first potential and a second potential that is smaller than the first potential. The first potential is 0 V or more. The second potential is 0 V or less. The switching period is 0.05 seconds or more.

[0007] According to the present invention, the etching rate can be increased.

[0008] A second aspect of the present invention is the substrate processing method of the first aspect, wherein the applied voltage is a DC voltage, and the switching period is 0.5 seconds or more.

[0009] A third aspect of the present invention is the substrate processing method according to the first aspect, wherein the applied voltage is an AC voltage, and the switching period is 0.2 seconds or more.

[0010] Aspect 4 of the present invention is a substrate processing method according to aspect 1 (which may be any one of aspects 1 to 3), wherein, in each switching period, the application time of the first voltage corresponding to the first potential is longer than the application time of the second voltage corresponding to the second potential.

[0011] A fifth aspect of the present invention is the substrate processing method of the first aspect (which may be any one of the first to fourth aspects), wherein the processing liquid is an etching liquid to which an electrolytic solution has been added to adjust the resistivity to 0.1 Ω m or less.

[0012] Aspect 6 of the present invention is the substrate processing method of Aspect 1 (which may be any one of Aspects 1 to 5), in which the processing target film contains one or more of TiN, TaN, TiAl, and TiAlC. ２ O ２ Includes.

[0013] A seventh aspect of the present invention is the substrate processing method of the first aspect (which may be any one of the first to sixth aspects), wherein the switching period is increased as the elapsed time from the start of the b) step increases.

[0014] Aspect 8 of the present invention is the substrate processing method of Aspect 1 (which may be any one of Aspects 1 to 7), wherein in the step a), the processing liquid is continuously supplied to the substrate, and the supply flow rate of the processing liquid is increased as the elapsed time from the start of the step b) increases.

[0015] A ninth aspect of the present invention is the substrate processing method of the first aspect (which may be any one of the first to eighth aspects), wherein in the step b), bubbles are generated in the recessed portion.

[0016] A tenth aspect of the present invention is the substrate processing method according to any one of the first to ninth aspects, wherein the recess has a width of 10 nm or less.

[0017] Aspect 11 of the present invention is a substrate processing apparatus for etching a substrate having a target film located in a recess of a pattern, the apparatus comprising: a substrate holding unit for holding the substrate; a processing liquid supply unit for supplying a conductive etching processing liquid to the substrate and bringing it into contact with the target film; a first electrode electrically connected to the substrate; a second electrode electrically connected to the processing liquid; a power supply unit for applying an applied voltage between the first electrode and the second electrode; and a power supply control unit for controlling the power supply unit to repeatedly switch the applied voltage between different first and second voltages at a predetermined switching period while the processing liquid is in contact with the target film, thereby repeatedly switching the potential of a sidewall surface forming the recess between a first potential and a second potential lower than the first potential. The first potential is 0 V or higher. The second potential is 0 V or lower. The switching period is 0.05 seconds or longer.

[0018] A twelfth aspect of the present invention is the substrate processing apparatus of the eleventh aspect, wherein the applied voltage is a DC voltage, and the switching period is 0.5 seconds or more.

[0019] A thirteenth aspect of the present invention is the substrate processing apparatus of the eleventh aspect, wherein the applied voltage is an AC voltage, and the switching period is 0.2 seconds or more.

[0020] Aspect 14 of the present invention is a substrate processing apparatus according to aspect 11 (which may be any one of aspects 11 to 13), wherein in each switching period, the application time of the first voltage corresponding to the first potential is longer than the application time of the second voltage corresponding to the second potential.

[0021] A fifteenth aspect of the present invention is the substrate processing apparatus of Aspect 11 (which may be any one of Aspects 11 to 14), wherein the processing liquid is an etching liquid to which an electrolytic solution is added to adjust the resistivity to 0.1 Ω m or less.

[0022] Aspect 16 of the present invention is the substrate processing apparatus of aspect 11 (which may be any one of aspects 11 to 15), in which the film to be processed contains one or more of TiN, TaN, TiAl, and TiAlC. ２ O ２ Includes.

[0023] Aspect 17 of the present invention is a substrate processing apparatus according to aspect 11 (which may be any one of aspects 11 to 16), wherein the power supply control unit increases the switching period as the elapsed time from the start of switching the applied voltage increases.

[0024] Aspect 18 of the present invention is the substrate processing apparatus of Aspect 11 (which may be any one of Aspects 11 to 17), further comprising a supply control unit that controls the processing liquid supply unit. The processing liquid is continuously supplied to the substrate while the power supply control unit repeatedly switches the applied voltage. The supply control unit increases the supply flow rate of the processing liquid from the processing liquid supply unit as the elapsed time from the start of switching the applied voltage increases.

[0025] Aspect 19 of the present invention is a substrate processing apparatus according to aspect 11 (which may be any one of aspects 11 to 18), in which bubbles are generated in the recess while the power supply control unit repeatedly switches the applied voltage.

[0026] A twentieth aspect of the present invention is the substrate processing apparatus according to any one of the eleventh to nineteenth aspects, wherein the recess has a width of 10 nm or less.

[0027] The above and other objects, features, aspects and advantages will become more apparent from the following detailed description of the invention which proceeds with reference to the accompanying drawings.

[0028] FIG. 1 is a plan view of a substrate processing system. FIG. 2 is a side view of a substrate processing apparatus according to an embodiment. FIG. 3 is a cross-sectional view showing an enlarged portion of a substrate. FIG. 4 is a diagram showing a substrate processing flow. FIG. 5 is a diagram showing a waveform of an applied voltage. FIG. 6 is a diagram showing a waveform of an applied voltage. FIG. 7 is a cross-sectional view showing an enlarged portion of a substrate. FIG. 8 is a cross-sectional view showing an enlarged portion of a substrate. FIG. 9 is a cross-sectional view showing an enlarged portion of a substrate. FIG. 10 is a cross-sectional view showing an enlarged portion of a substrate. FIG. 11 is a cross-sectional view showing an enlarged portion of a substrate. FIG. 12 is a diagram showing an experimental apparatus. FIG. 13 is a cross-sectional view showing an enlarged portion of a substrate.

[0029] 1 is a schematic plan view showing the layout of a substrate processing system 10. The substrate processing system 10 processes 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.

[0030] 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.

[0031] The processing block 102 includes a plurality of (e.g., 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.

[0032] Fig. 2 is a side view showing the configuration of a substrate processing apparatus 1 according to one embodiment of the present invention. The substrate processing apparatus 1 is a single-wafer type apparatus that processes substrates 9 one by one. The substrate processing apparatus 1 is an apparatus that performs etching on the upper main surface (hereinafter also referred to as "upper surface 91") of the substrate 9. Fig. 2 shows a cross section of a portion of the configuration of the substrate processing apparatus 1.

[0033] The substrate processing apparatus 1 includes a substrate holding unit 31, a substrate rotation mechanism 33, a cup unit 4, a processing liquid supply unit 5, a voltage application unit 6, a housing 11, and a control unit 8. The substrate holding unit 31, the substrate rotation mechanism 33, the cup unit 4, and the like are housed in the internal space of the housing 11. An airflow forming unit 12 is provided in the canopy of the housing 11, and supplies gas to the internal space to form a downward airflow (so-called downflow). For example, an FFU (fan filter unit) is used as the airflow forming unit 12. The control unit 8 is disposed outside the housing 11 and controls the substrate holding unit 31, the substrate rotation mechanism 33, the processing liquid supply unit 5, the voltage application unit 6, and the like.

[0034] The control unit 8 is a general computer system including, for example, a CPU, ROM, RAM, a fixed disk, a display, an input unit, a reading device, a communication unit, and a bus. The CPU executes arithmetic processing using the RAM and the fixed disk in accordance with a program. The control unit 8 includes a power supply control unit 81 and a supply control unit 82 as functions realized by the CPU and the like. The power supply control unit 81 controls the power supply unit 63 of the voltage application unit 6. The supply control unit 82 controls the treatment liquid supply unit 5. 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.

[0035] The substrate holder 31 and substrate rotation mechanism 33 shown in FIG. 2 are each part of a spin chuck that holds and rotates a substantially disk-shaped substrate 9. The substrate holder 31 holds the horizontally positioned substrate 9 from below. The substrate holder 31 is, for example, a vacuum chuck that holds the substrate 9 by suction. The substrate holder 31 includes a substantially disk-shaped base portion 311 that contacts and suctions the center of the lower main surface (hereinafter also referred to as the "lower surface 92") of the substrate 9. In the example shown in FIG. 2, the diameter of the base portion 311 is smaller than the diameter of the substrate 9. Note that the shape and structure of the substrate holder 31 may be modified in various ways. For example, the substrate holder 31 may be a mechanical chuck that mechanically holds the substrate 9.

[0036] 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 that extends substantially parallel to the vertical direction. 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 vertical direction and is connected to the center of the underside of the base unit 311 of the substrate holding unit 31. The motor 332 is an electric rotary motor that rotates the shaft 331. Note that the substrate rotation mechanism 33 may be a motor having another structure (e.g., a hollow motor, etc.).

[0037] The processing liquid supply unit 5 supplies a processing liquid to the substrate 9 and performs liquid processing on the substrate 9. The processing liquid supply unit 5 is controlled by a supply control unit 82 of the control unit 8. In the example shown in Fig. 2, the processing liquid supply unit 5 includes a nozzle 51 that ejects the processing liquid from above the substrate 9 toward an upper surface 91 of the substrate 9. The nozzle 51 is supported by, for example, an arm 52 that extends substantially horizontally. An end of the arm 52 opposite to the nozzle 51 is connected to a nozzle moving mechanism 53.

[0038] The nozzle movement mechanism 53 moves the nozzle 51 horizontally by rotating the arm 52 in the horizontal direction. The nozzle 51 is movable, for example, between a supply position above the substrate 9 and a retracted position located outside the outer edge of the substrate 9 in a radial direction (hereinafter simply referred to as the "radial direction") centered on the rotation axis J1. The nozzle movement mechanism 53 also moves the arm 52 up and down to raise and lower the nozzle 51. The nozzle movement mechanism 53 includes, for example, an electric linear motor, an air cylinder, or a ball screw and an electric rotary motor.

[0039] The nozzle 51 ejects a conductive processing liquid toward the upper surface 91 of the substrate 9, and brings the processing liquid into contact with the processing target film provided on the upper surface 91 of the substrate 9. The processing liquid contains an etchant used to etch the processing target film on the substrate 9. The etchant is, for example, hydrogen peroxide (H ２ O ２ ), hydrofluoric acid (HF), nitric acid (HNO ３ ), ammonia (NH ３ ), TMAH (tetramethylammonium hydroxide), or TBAH (tetrabutylammonium hydroxide), etc. The etchant contained in the processing liquid may be one other than those mentioned above.

[0040] In addition to the nozzle 51, the processing liquid supply unit 5 may include another nozzle that ejects a different type of processing liquid toward the substrate 9 from the processing liquid ejected from the nozzle 51. The processing liquid ejected from the other nozzle is, for example, a rinse liquid such as DIW (deionized water) that is used for rinsing the substrate 9. Alternatively, the nozzle 51 may be capable of ejecting another type of processing liquid (for example, a rinse liquid) in addition to the processing liquid used for the etching described above.

[0041] The voltage application unit 6 includes a first electrode 61, a second electrode 62, and a power supply unit 63. The first electrode 61 is provided, for example, inside the base portion 311 of the substrate holding unit 31 and is electrically connected to the substrate holding unit 31. In other words, the substrate holding unit 31 is a conductive chuck with the first electrode 61 built in. The first electrode 61 is electrically connected to the substrate 9 held by the substrate holding unit 31 via the substrate holding unit 31. Note that the first electrode 61 does not necessarily have to be built into the substrate holding unit 31, and may be disposed outside the substrate holding unit 31 and electrically connected to the substrate holding unit 31.

[0042] 2 , the second electrode 62 is attached to the nozzle 51 and electrically connected to the nozzle 51. The second electrode 62 is attached, for example, near the outlet at the lower end of the nozzle 51. The second electrode 62 is electrically connected, via the nozzle 51, to the processing liquid that is ejected from the nozzle 51 toward the substrate 9. The second electrode 62 is formed of a material that is highly chemical-resistant and conductive. The second electrode 62 is formed, for example, of platinum (Pt) or glassy carbon (GC).

[0043] The power supply unit 63 is electrically connected to the first electrode 61 and the second electrode 62 via electric wires. The power supply unit 63 applies a voltage between the first electrode 61 and the second electrode 62. In the following description, the voltage applied between the first electrode 61 and the second electrode 62 by the power supply unit 63 is also referred to as the "applied voltage." For example, a power supply capable of applying DC voltage and AC voltage is used as the power supply unit 63. The power supply unit 63 is controlled by the power supply control unit 81 of the control unit 8. The structure and type of the power supply unit 63 may be modified in various ways. The arrangement, shape, and structure of the first electrode 61 and the second electrode 62 may also be modified in various ways.

[0044] 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 in the circumferential direction (hereinafter simply referred to as the "circumferential direction") around the rotation axis J1, covering 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 periphery 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 drain 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.

[0045] The cup lifting mechanism described above 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 can move the cup 41 in the vertical direction between a processing position around the substrate 9 shown in FIG. 2 and a retracted position below the processing position.

[0046] 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.

[0047] Fig. 3 is an enlarged cross-sectional view of a portion of the substrate 9. The example shown in Fig. 3 shows two microstructures 94 out of many microstructures 94 that make up a micropattern (hereinafter also referred to as a "micropattern 93") provided on the surface of the substrate 9. The microstructures 94 are microstructures provided on the upper surface of a substrate body made of silicon (Si), and may be, for example, structures made of a single type of material or layered structures made by stacking multiple types of materials.

[0048] The microstructure 94 is, for example, a nanosheet channel of a GAA (gate all around) structure, and the recess 95 is a trench between the nanosheet channels. The processed film 96 is a metal gate electrode material in a RMG (replacement metal gate). A sidewall surface 942 of the microstructure 94 that forms the recess 95 (i.e., the inner surface of the recess 95) is, for example, SiO ２ The dielectric constant of the dielectric layer is higher than that of silicon dioxide (silicon dioxide). Examples of the high-k material include hafnium-based, tungsten-based, and cobalt-based materials.

[0049] The two microstructures 94 extend substantially linearly in a direction (hereinafter also referred to as the "longitudinal direction") substantially perpendicular to the plane of the paper in Fig. 3. That is, Fig. 3 shows longitudinal cross sections of the two microstructures 94, as well as a longitudinal cross section of a recess 95, which is a minute gap provided between the two microstructures 94.

[0050] The width of the recess 95 in the width direction perpendicular to the longitudinal direction (i.e., the up-down direction in FIG. 3 ) is, for example, 10 nm or less. The depth of the recess 95 in the left-right direction in FIG. 3 is, for example, 20 nm or more. Furthermore, the aspect ratio, which is the ratio of the depth to the width of the recess 95 (i.e., the value obtained by dividing the depth of the recess 95 by the width), is, for example, 5 or more.

[0051] The recess 95 may be a recess other than a trench, such as a hole that is substantially circular in plan view. When the recess 95 is a hole, the width of the recess 95 described above is the diameter of the hole in plan view.

[0052] FIG. 3 shows the substrate 9 before etching by the substrate processing apparatus 1. In the substrate 9 before etching, the interior of the recess 95 and the end faces 941 of the two microstructures 94 are covered with a film 96 to be processed. The film 96 to be processed is, for example, a conductive film formed of a conductor. The film 96 to be processed is, for example, a metal film containing one or more metals selected from titanium (Ti), tantalum (Ta), tungsten (W), copper (Cu), and aluminum (Al). The film 96 to be processed contains, for example, at least one of titanium nitride (TiN), tantalum nitride (TaN), titanium aluminum (TiAl), and titanium aluminum carbide (TiAlC). Note that the film 96 to be processed may be formed of a material other than the above (e.g., MnO). The thickness of the film 96 to be processed on the end faces 941 of the microstructures 94 (i.e., the thickness in the left-right direction in FIG. 3 ) is, for example, 1 nm or more and 5 nm or less.

[0053] Next, the flow of processing the substrate 9 in the substrate processing apparatus 1 will be described with reference to Fig. 4. When the substrate 9 is processed, the substrate 9 is first loaded into the substrate processing apparatus 1 and held substantially horizontally by the substrate holder 31 (step S11). When the substrate 9 is loaded, the nozzle 51 is located in the retracted position described above. Next, the nozzle 51 is moved radially inward by the nozzle moving mechanism 53, and is located in the processing position above the substrate 9, as shown in Fig. 2.

[0054] Next, the control unit 8 drives the substrate rotation mechanism 33, thereby starting the rotation of the substrate 9. Furthermore, the supply control unit 82 of the control unit 8 controls the processing liquid supply unit 5, thereby supplying the processing liquid for etching from the nozzle 51 to the upper surface 91 of the substrate 9. The processing liquid spreads over the entire upper surface 91 of the substrate 9 due to the centrifugal force caused by the rotation of the substrate 9, and comes into contact with the processing target film 96 on the substrate 9 (step S12). The centrifugal force caused by the rotation of the substrate 9 causes the processing liquid to splash radially outward from the outer periphery of the substrate 9, and is received by the cup unit 4.

[0055] In this embodiment, the film 96 to be processed is a conductive film made of titanium nitride (TiN), and the sidewall surface 942 of the microstructure 94 is made of hafnium oxide (HfO２ The treatment liquid is a conductive liquid obtained by adding an electrolyte to hydrogen peroxide solution, which is an etching liquid. The resistivity of the treatment liquid is, for example, 0.1 Ω·m or less, and preferably 0.05 Ω·m or less. The electrolyte may be, for example, hydrochloric acid (HCl), sulfuric acid (H ２ SO ４ ), an aqueous solution of ammonia, etc. can be used. The resistivity of the treatment liquid may be higher than 0.1 Ω·m. The treatment liquid may also be a hydrogen peroxide solution alone without adding hydrochloric acid, etc. The treatment liquid may also be SC2, which is a mixed solution of hydrogen peroxide and an aqueous hydrochloric acid solution.

[0056] In the substrate processing apparatus 1, in parallel with step S12, the power supply control unit 81 controls the power supply unit 63 to apply a voltage between the first electrode 61 and the second electrode 62. As a result, a voltage is applied between the substrate 9 and the processing liquid on the substrate 9. The voltage applied between the substrate 9 and the processing liquid is repeatedly switched between a first voltage and a second voltage, which are different from each other, at a predetermined switching period under the control of the power supply control unit 81. As a result, the potential of the sidewall surface 942 of the microstructure 94 is repeatedly switched between the first potential and the second potential at the switching period (step S13).

[0057] The power supply unit 63 applies a voltage to the first electrode 61 with the potential of the second electrode 62 as a reference, and the first and second potentials are potentials with the second electrode 62 as a reference. The second electrode 62 is set to approximately the same potential as the processing liquid on the substrate 9. The first potential is 0 V (volts) or higher. The second potential is 0 V or lower and is smaller than the first potential. Therefore, when the first potential is 0 V, the second potential is less than 0 V. The first potential is, for example, +8 V or lower. The second potential is, for example, -8 V or higher. The upper limit of the first potential and the lower limit of the second potential may be changed in various ways.

[0058] The switching period is 0.05 seconds or more. Preferably, the switching period is 20 seconds or less. When the applied voltage is a DC voltage, the switching period is preferably 0.5 seconds or more, more preferably 1 second or more, and even more preferably 2 seconds or more. When the applied voltage is a DC voltage, the switching period is preferably 18 seconds or less, more preferably 12 seconds or less, and even more preferably 6 seconds or less.

[0059] When the applied voltage is an AC voltage, the above-mentioned switching period of 0.05 seconds or more corresponds to a frequency of 20 Hz or less, and a switching period of 20 seconds or less corresponds to a frequency of 0.05 Hz or more. When the applied voltage is an AC voltage, the switching period is preferably 0.1 seconds or more (i.e., a frequency of 10 Hz or less), and more preferably 0.2 seconds or more (i.e., a frequency of 5 Hz or less). When the applied voltage is an AC voltage, the switching period is preferably 2 seconds or less (i.e., a frequency of 0.5 Hz or more), and more preferably 1 second or less (i.e., a frequency of 1 Hz or more).

[0060] The switching of the applied voltage in step S13 (i.e., the switching of the potential of the sidewall surface 942) is continued while the processing liquid is being supplied in step S12. In this way, by switching the applied voltage between the first electrode 61 and the second electrode 62 while the processing liquid is being supplied to the substrate 9, the processing target film 96 provided in the recess 95 is etched and the processing target film 96 is removed from the substrate 9. Note that, as long as step S13 is performed in parallel with step S12, it may be started, for example, before the start of step S12 or after a predetermined time has passed since the start of step S12.

[0061] 5A and 5B are diagrams showing examples of the waveform of the applied voltage applied from the power supply unit 63 in step S13. FIG. 5A shows an example of the waveform when the applied voltage is a DC voltage, and FIG. 5B shows an example of the waveform when the applied voltage is an AC voltage. In FIG. 5, the horizontal axis represents elapsed time, and the vertical axis represents the applied voltage applied between the first electrode 61 and the second electrode 62. In this specification, when the potential of the first electrode 61 is higher than the potential of the second electrode 62, the applied voltage is considered positive, and when the potential of the first electrode 61 is lower than the potential of the second electrode 62, the applied voltage is considered negative. In the following description, when the applied voltage is positive, it is also expressed as "a positive voltage is applied to the first electrode 61," and when the applied voltage is negative, it is also expressed as "a negative voltage is applied to the first electrode 61."

[0062] In the example shown in Figure 5A, the waveform of the applied voltage is a square wave. The maximum value of the applied voltage (i.e., the first voltage) is +8 V, and the minimum value of the applied voltage (i.e., the second voltage) is -8 V. As described above, the applied voltage is changed over a predetermined switching period T Ｄ In the following description, the applied voltage is repeatedly switched between the first voltage and the second voltage at each switching period T Ｄ The time during which the applied voltage is positive is referred to as the "first application time T Ｄｐ ", and the time when the applied voltage is negative is called the "second application time T Ｄｍ In the example shown in FIG. 5A, the first application time T Ｄｐ and the second application time T Ｄｍ is the same as T Ｄ The first voltage and the second voltage may be changed as appropriate, and the absolute values ​​thereof do not need to be the same. Ｄｐ and the second application time T Ｄｍ are not necessarily the same and may be different.

[0063] FIG. 5B shows an example of a waveform when the applied voltage is an AC voltage. In the example shown in FIG. 5B, the waveform of the AC voltage is a sine wave. The vertical axis of FIG. 5B shows the instantaneous value of the applied voltage. The maximum value of the applied voltage (i.e., the first voltage) is +8 V, and the minimum value of the applied voltage (i.e., the second voltage) is −8 V. As described above, the applied voltage is changed at a predetermined switching period TＡ In the following description, the applied voltage is repeatedly switched between the first voltage and the second voltage at each switching period T Ａ The time during which the applied voltage is positive is referred to as the "first application time T Ａｐ ", and the time when the applied voltage is negative is called the "second application time T Ａｍ In the example shown in FIG. 5B, the first application time T Ａｐ and the second application time T Ａｍ is the same as T Ａ The first voltage and the second voltage may be changed as appropriate, and the absolute values ​​thereof do not need to be the same. Ａｐ and the second application time T Ａｍ When the applied voltage is an AC voltage, the waveform of the applied voltage is not limited to a sine wave, and may be, for example, a triangular wave or a sawtooth wave.

[0064] In step S13, the power supply control unit 81 controls the power supply unit 63, and the applied voltage is repeatedly switched between the first voltage and the second voltage. This promotes etching of the target film 96 and increases the etching rate. In particular, etching of the target film 96 within the recess 95 is promoted and increases the etching rate.

[0065] The mechanism by which the etching rate increases by repeatedly switching the applied voltage is not fully understood. Below, several possible mechanisms are described.

[0066] First, the first principle will be described with reference to FIGS. 6A to 6D , which are cross-sectional views similar to those of FIG. 3 . FIGS. 6A to 6D show a state in which etching of the film 96 shown in FIG. 3 has progressed to a certain extent, with the film 96 on the end surface 941 of the microstructure 94 being removed and the film 96 inside the recess 95 also being slightly removed. To simplify the illustrations, FIGS. 6A to 6D also show a schematic representation in which the surface of the film 96 (i.e., the end surface opposite the bottom of the recess 95, i.e., the surface on the left side in the figure) is perpendicular to the left-right direction. The same applies to FIGS. 7A to 7D , which will be described later. In the examples shown in FIGS. 6A to 6D , the etching liquid used for etching will be described as containing hydrogen peroxide as an etchant.

[0067] 6A shows a state in which a positive voltage is applied to the first electrode 61 (see FIG. 2 ). By applying a positive voltage to the first electrode 61, the surface of the film 96 to be treated within the recess 95 becomes positively charged. Furthermore, the sidewall surfaces 942 (i.e., the inner surfaces of the recess 95) and end faces 941 of the two microstructures 94 located on either side of the recess 95 also become positively charged. Therefore, the hydrogen peroxide molecules 71 and water molecules 72, which are polar molecules (also called polar molecules), are adsorbed onto the surface of the film 96 to be treated and the surface of the microstructure 94 (i.e., the sidewall surfaces 942 and end faces 941). Specifically, the negatively charged portions of the hydrogen peroxide molecules 71 and the negatively charged portions of the water molecules 72 are adsorbed onto the surfaces of the film 96 to be treated and the microstructure 94.

[0068] In Figure 6A, hydrogen peroxide molecules 71 are schematically represented by circles, and the bias in the charge of the hydrogen peroxide molecules 71 is indicated by arrows inside the circles. Specifically, the portion of the hydrogen peroxide molecule 71 where the positive charge is biased is indicated by the arrowhead (i.e., the arrowhead), and the portion where the negative charge is biased is indicated by the end opposite the arrowhead. The same is true for water molecules 72. Note that the circle schematically representing the water molecule 72 is drawn smaller than the circle schematically representing the hydrogen peroxide molecule 71. The same is true for Figures 6B and 6D.

[0069] When a positive voltage is applied to the first electrode 61, the target film 96 is etched by the hydrogen peroxide molecules 71 adsorbed on the surface of the target film 96. The hydrogen peroxide molecules 71 used to etch the target film 96 also convert into hydroxide ions (OH － ) and disappear from the surface of the film 96 to be treated. Therefore, as etching of the film 96 to be treated progresses, the hydrogen peroxide molecules 71 decrease or disappear on the surface of the film 96 to be treated and on the surface of the microstructure 94 in the vicinity of the film 96 to be treated (i.e., the inner surface of the recess 95), and as shown in FIG. 6B , the surface of the film 96 to be treated and the inner surface of the recess 95 are covered with water molecules 72. As a result, adsorption of the hydrogen peroxide molecules 71 to the surface of the film 96 to be treated is inhibited, and the etching rate of the film 96 to be treated decreases or etching of the film 96 to be treated stops.

[0070] Therefore, in the substrate processing apparatus 1, the positive and negative voltages applied to the first electrode 61 are switched at a predetermined timing, and a negative voltage is applied to the first electrode 61, thereby negatively charging the surfaces of the film 96 to be processed and the microstructure 94, as shown in Fig. 6C. As a result, water molecules 72 adsorbed to the surfaces of the film 96 to be processed and the microstructure 94 (e.g., the inner surfaces of the recesses 95) are electrolyzed into hydrogen molecules and hydroxide ions, and are removed from the surfaces of the film 96 to be processed and the microstructure 94. As a result, the surface of the film 96 to be processed becomes capable of adsorbing hydrogen peroxide molecules 71.

[0071] In the substrate processing apparatus 1, the positive and negative voltages applied to the first electrode 61 are switched at predetermined timing, and a positive voltage is applied to the first electrode 61, thereby positively charging the film to be processed 96 and the surfaces of the microstructure 94 (e.g., the inner surfaces of the recesses 95), as shown in Fig. 6D. This causes hydrogen peroxide molecules 71 to be adsorbed onto the surface of the film to be processed 96, and the film to be processed 96 is etched by the hydrogen peroxide molecules 71. As a result, etching of the film to be processed 96 in the recesses 95 is accelerated, and the etching rate is increased.

[0072] Next, the second principle will be described with reference to FIGS. 7A to 7D . FIG. 7A shows a state in which a positive voltage is applied to the first electrode 61 (see FIG. 2 ). By applying a positive voltage to the first electrode 61, the sidewall surfaces 942 of the two microstructures 94 located on both sides of the recess 95 (i.e., the inner surfaces of the recess 95) become positively charged. In other words, the potential of the sidewall surfaces 942 of the microstructures 94 becomes higher than the potential of the treatment solution. This makes it easier for negative ions 73, which are etchant present around the recess 95, to enter the recess 95. As a result, contact between the surface of the treatment film 96 and the negative ions 73, which are etchant, increases, accelerating etching of the treatment film 96.

[0073] As etching of the target film 96 progresses, negatively charged by-products 74 generated by etching increase and remain in the recess 95, making it difficult for the negative ions 73, which serve as etchants, to enter the recess 95, as shown in Fig. 7B. As a result, contact between the negative ions 73 and the target film 96 decreases, and the etching rate of the target film 96 decreases, or etching of the target film 96 stops. In Fig. 7B, the by-products 74 are indicated by hatched lines to facilitate understanding of the drawing (the same applies to Fig. 7C).

[0074] Therefore, the positive and negative voltages applied to the first electrode 61 are switched at a predetermined timing, and a negative voltage is applied to the first electrode 61. As a result, as shown in FIG. 7C , the sidewall surfaces 942 of the two microstructures 94 located on both sides of the recess 95 (i.e., the inner surfaces of the recess 95) become negatively charged. In other words, the potential of the sidewall surfaces 942 of the microstructures 94 becomes lower than the potential of the treatment solution. As a result, the positive ions 75 present around the recess 95 enter the recess 95, and the product 74 remaining in the recess 95 is expelled to the outside of the recess 95.

[0075] Thereafter, the positive and negative voltages applied to the first electrode 61 are switched at a predetermined timing, and a positive voltage is applied to the first electrode 61. As a result, as shown in Fig. 7D, the sidewall surface 942 of the microstructure 94 (i.e., the inner surface of the recess 95) is positively charged. As a result, negative ions 73, which are etchant present around the recess 95, enter the recess 95 and come into contact with the film 96 to be treated, thereby accelerating etching of the film 96 to increase the etching rate.

[0076] Next, the third principle will be described. In the etching of the target film 96 described above, positive and negative voltages are alternately applied to the first electrode 61. It has been confirmed that bubbles are generated in the recess 95 when one of the positive and negative voltages is applied, but no bubbles are generated when the other voltage is applied. Therefore, if only one of the positive and negative voltages is continuously applied to the first electrode 61, bubbles increase and remain in the recess 95, reducing the etching rate of the target film 96 or stopping etching of the target film 96. Therefore, by switching the positive and negative polarities of the voltage applied to the first electrode 61 at a predetermined timing, the bubbles are expelled from the recess 95. This suppresses etching inhibition due to bubbles and increases the etching rate.

[0077] Next, the fourth principle will be described. In the following description, the target film 96 is a TiN film, and the processing solution used for etching is an aqueous solution of hydrogen peroxide to which hydrochloric acid is added as an electrolyte. When a positive voltage is applied to the first electrode 61, chlorine ions (Cl ), which are ligands in the processing solution, are ionized. － ) easily penetrates into the recess 95. This accelerates etching of the film 96 to be treated, increasing the etching rate. As etching progresses, the complex (Ti—Cl) generated by the etching increases and remains in the recess 95, making it difficult for the ligand to penetrate into the recess 95. As a result, the etching rate of the film 96 to be treated decreases, or etching of the film 96 to be treated stops.

[0078] Therefore, the positive and negative voltages applied to the first electrode 61 are switched at a predetermined timing, and a negative voltage is applied to the first electrode 61, thereby expelling the complex from the recess 95. Thereafter, a positive voltage is applied to the first electrode 61, which makes it easier for the ligands in the treatment liquid to enter the recess 95, as described above. This promotes etching of the treatment target film 96, and increases the etching rate.

[0079] It is not clear which of the first to fourth principles is dominant. The increase in etching rate may be due to a combination of these principles with other principles, or may be due to a principle other than these. In any case, however, in step S13, the applied voltage is repeatedly switched at a switching cycle of 0.05 seconds or more, and the potential of the sidewall surface 942 of the microstructure 94 is repeatedly switched between the first potential and the second potential, thereby accelerating etching of the film 96 to be processed in the recess 95.

[0080] 2 , after a predetermined processing time has elapsed since the start of step S12 or step S13, the supply of processing liquid to substrate 9 and the application of voltage by power supply unit 63 are stopped, and etching of substrate 9 is stopped. When etching is completed, for example, nozzle 51 is retracted from the processing position to the retracted position, and a rinse liquid is supplied to upper surface 91 of substrate 9 from another nozzle (not shown). The rinse liquid is spread over the entire upper surface 91 of substrate 9 by centrifugal force caused by the rotation of substrate 9. This performs a rinse process to wash away the processing liquid and the like adhering to substrate 9 (step S14). The rinse liquid is scattered radially outward from the outer periphery of substrate 9 by centrifugal force caused by the rotation of substrate 9 and is received by cup unit 4.

[0081] After the substrate 9 has been rinsed for a predetermined time, the supply of the rinse liquid is stopped. 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 S15). The drying process may be performed by various known methods. 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 1.

[0082] Next, with reference to Tables 1 to 7, Examples 1 to 28 and Comparative Examples 1 to 3 for etching the film 96 to be processed will be described.

[0083]

[0084]

[0085]

[0086]

[0087]

[0088]

[0089]

[0090] In Examples 1 to 28 and Comparative Example 2, etching of a film 96 to be processed in the substrate processing apparatus 1 was simulated, and a test piece 98 was subjected to the processes corresponding to the above-described steps S11 to S15 in an experimental apparatus 97 shown in FIG. 8. In Comparative Examples 1 and 3, a test piece 98 was subjected to the processes corresponding to the above-described steps S11 to S12 and S14 to S15 in the experimental apparatus 97. That is, in Comparative Examples 1 and 3, the application of voltage in step S13 was omitted. Note that these processes on the test piece 98 were performed in an air atmosphere at room temperature (e.g., 25°C).

[0091] The experimental device 97 includes an electrolytic cell 971, a test piece electrode 972, a counter electrode 973, a reference electrode 974, and a potentiostat 975. A "VM-3" manufactured by EC Frontier Co., Ltd. was used as the electrolytic cell 971. A test piece 98 was set on a base 976 of the electrolytic cell 971, and a cell cap 977 on the base 976 was filled with a treatment solution for etching. The upper surface of the test piece 98 comes into contact with the treatment solution in the cell cap 977. The contact area of ​​the test piece 98 with the treatment solution was limited to 1 cm by an O-ring. ２ The upper surface of the test piece 98 is provided with a plurality of microstructures 94 that form a plurality of the recesses 95 (see FIG. 3) described above.

[0092] An alligator clip was used as the test strip electrode 972 corresponding to the first electrode 61 (see FIG. 2 ). The test strip electrode 972 and the test strip 98 were electrically connected by clamping the end of the test strip 98 with the alligator clip. The counter electrode 973 was a "CE-100" manufactured by EC Frontier Co., Ltd. The reference electrode 974 was an "RE-T16" manufactured by EC Frontier Co., Ltd. The "RE-T16" is a silver-silver chloride electrode (Ag / AgCl electrode) that uses a potassium chloride (KCl) aqueous solution with a concentration of 3.0 mol / L (moles / liter) as the internal solution. The potential relative to the NHE (standard hydrogen electrode) is +0.208 V at 25°C. The counter electrode 973 and reference electrode 974 are inserted into the cell cap 977 from the top and come into contact with the treatment solution inside the cell cap 977. As the potentiostat 975, a "VSP-300-SC" manufactured by Bio-Logic Science was used.

[0093] In Examples 1 to 17 and Comparative Examples 1 and 2 shown in Tables 1 to 4, the etching process was performed using SC2 as the treatment liquid, with a treatment time of 60 minutes (i.e., the treatment time of step S12). The treatment liquid was a mixture of approximately 20 mol% hydrogen peroxide, approximately 22 mol% hydrochloric acid, and DIW in a volume ratio of 1:1:8.

[0094] In Examples 18 to 28 and Comparative Example 3 shown in Tables 5 to 7, the treatment liquid used in the etching process was hydrogen peroxide, and the treatment time of the etching process (i.e., the treatment time of step S12) was 120 minutes. The treatment liquid was a mixture of hydrogen peroxide with a concentration of approximately 20 mol% and DIW in a volume ratio of 1:8. No other chemicals such as hydrochloric acid were added to the treatment liquid. In other words, the concentration of hydrochloric acid in the treatment liquid was 0 mol%, or 0 mass%.

[0095] The etching amount in Tables 1 to 7 is a distance D1 in the depth direction of the recess 95 (i.e., the left-right direction in FIG. 9 ) between a surface 961 of the film to be treated 96 in a state before the start of etching, as indicated by a two-dot chain line in FIG. 9 , and a surface 962 of the film to be treated 96 in a state after etching for a predetermined time, as indicated by a solid line in FIG. 9 . Note that, as shown in FIG. 9 , the distance D1 is the distance between the surface 961 of the film to be treated 96 and the lowest end of the surface 962 of the film to be treated 96 in the recess 95 (i.e., the position farthest from the surface 961 in the depth direction). The etching amount is the arithmetic average of the distances D1 in each of the six recesses 95. The distance D1 can be determined by observing an SEM image of a cross section of the substrate 9.

[0096] As described above, in Examples 1 to 17 and Comparative Examples 1 and 2 shown in Tables 1 to 4, SC2 was used as the processing liquid. In Examples 1 to 5 shown in Table 1, the etching amount of the target film 96 was measured by changing the first and second voltages applied in step S13. In Example 1, the applied voltage applied from the power supply unit 63 was a DC voltage, with the second voltage being −8 V and the first voltage being +8 V. The applied voltage switching period was 6 seconds. That is, in Example 1, the potential on the sidewall surface 942 of the microstructure 94 (i.e., the inner surface of the recess 95) was switched between the second potential of −8 V and the first potential of +8 V with a switching period of 6 seconds. In Example 1, the etching amount was 24 nm.

[0097] Example 2 is similar to Example 1, except that the second voltage is −1 V and the first voltage is +1 V. In Example 2, the potential on the sidewall surface 942 of the microstructure 94 is switched between the second potential of −1 V and the first potential of +1 V with a switching period of 6 seconds. In Example 2, the etching amount was 26 nm.

[0098] Example 3 is similar to Example 1 except that the second voltage is −0.8 V and the first voltage is +0.8 V. In Example 3, the potential on the sidewall surface 942 of the microstructure 94 is switched between the second potential of −0.8 V and the first potential of +0.8 V at a switching period of 6 seconds. In Example 3, the etching amount was 25.5 nm.

[0099] Example 4 is similar to Example 1 except that the second voltage is −0.6 V and the first voltage is +0.6 V. In Example 4, the potential on the sidewall surface 942 of the microstructure 94 is switched between the second potential of −0.6 V and the first potential of +0.6 V at a switching period of 6 seconds. In Example 4, the etching amount was 25.5 nm.

[0100] Example 5 is similar to Example 1 except that the second voltage is −0.5 V and the first voltage is +0.5 V. In Example 5, the potential on the sidewall surface 942 of the microstructure 94 is switched between the second potential of −0.5 V and the first potential of +0.5 V at a switching period of 6 seconds. In Example 5, the etching amount was 27.5 nm.

[0101] In Comparative Example 1, as described above, the application of voltage in step S13 was omitted. In Comparative Example 1, the etching amount was 11 nm.

[0102] Comparing Examples 1 to 5 with Comparative Example 1, it can be seen that by performing step S13 (switching the applied voltage), the etching rate for the processed film 96 in the recess 95 increases even when the applied voltage is different.

[0103] In Examples 6 to 10 and Comparative Example 2 shown in Table 2, the etching amount of the target film 96 was measured by changing the first and second voltages applied in step S13. In Example 6, the applied voltage applied from the power supply unit 63 was a DC voltage, with the second voltage being −8 V and the first voltage being 0 V. The applied voltage switching cycle was 6 seconds. That is, in Example 6, the potential on the sidewall surface 942 of the microstructure 94 (i.e., the inner surface of the recess 95) was switched between the second potential of −8 V and the first potential of 0 V with a switching cycle of 6 seconds. In Example 6, the etching amount was 26 nm.

[0104] Example 7 is similar to Example 6, except that the first voltage is +1 V. In Example 7, the potential on the sidewall surface 942 of the microstructure 94 is switched between the second potential of −8 V and the first potential of +1 V with a switching period of 6 seconds. In Example 7, the etching amount was 25.5 nm.

[0105] Example 8 is similar to Example 6, except that the power supply unit 63 was turned off at the scheduled time for applying the first voltage. When the power supply unit 63 was turned off, the open circuit potential on the surface of the test piece 98 was +0.6 V to +0.8 V. In Example 8, the potential on the sidewall surface 942 of the microstructure 94 was switched between the second potential of −8 V and the above-mentioned open circuit potential as the first potential, with a switching period of 6 seconds. In Example 8, the etching amount was 25.5 nm.

[0106] Example 9 is similar to Example 6, except that the first voltage is +8 V. In Example 9, the potential on the sidewall surface 942 of the microstructure 94 is switched between the second potential of −8 V and the first potential of +8 V with a switching period of 6 seconds. In Example 9, the etching amount was 27 nm.

[0107] Example 10 is similar to Example 7, except that the second potential is −1 V. In Example 10, the potential on the sidewall surface 942 of the microstructure 94 is switched between the second potential of −1 V and the first potential of +1 V with a switching period of 6 seconds. In Example 10, the etching amount was 25.5 nm.

[0108] In addition, the experimental conditions of Examples 9 and 10 are the same as those of Examples 1 and 2 in Table 1, but the etching amount is slightly different from that of Examples 1 and 2 due to differences in the experimental date, etc. In other Examples, if the etching amount is different despite the same experimental conditions, this is also due to differences in the experimental date, etc.

[0109] Comparative Example 2 is similar to Example 6, except that the first voltage is −2 V. In Comparative Example 2, the potential on the sidewall surface 942 of the microstructure 94 is switched between −8 V and −2 V with a switching period of 6 seconds. In Comparative Example 2, the etching amount was 11 nm, which is substantially the same as in Comparative Example 1 (see Table 1).

[0110] Comparing Examples 6 to 10 with Comparative Example 2, it is found that when step S13 (switching of applied voltage) is performed, if the first potential and the second potential of the sidewall surface 942 are both negative (i.e., have the same sign) (Comparative Example 2), the etching rate does not increase. On the other hand, when the first potential and the second potential of the sidewall surface 942 do not have the same sign, even if the absolute values ​​of the first potential and the second potential are different (Examples 6 to 8), the etching rate for the film to be processed 96 in the recess 95 increases in substantially the same way as when the absolute values ​​of the first potential and the second potential are the same (Examples 9 and 10).

[0111] In Examples 11 to 14 shown in Table 3, the etching amount of the target film 96 was measured by changing the switching cycle of the applied voltage in step S13. In Example 11, the applied voltage applied from the power supply unit 63 was a DC voltage, with the second voltage being −1 V and the first voltage being +1 V. The switching cycle of the applied voltage was 2 seconds. That is, in Example 11, the potential on the sidewall surface 942 of the microstructure 94 (i.e., the inner surface of the recess 95) was switched between the second potential of −1 V and the first potential of +1 V with a switching cycle of 2 seconds. In Example 11, the etching amount was 20.5 nm.

[0112] Example 12 is similar to Example 11, except that the switching period is set to 6 seconds. In Example 12, the potential on the sidewall surface 942 of the microstructure 94 is switched between the second potential of −1 V and the first potential of +1 V with a switching period of 6 seconds. In Example 12, the etching amount was 21.5 nm.

[0113] Example 13 is similar to Example 11, except that the switching period is set to 12 seconds. In Example 13, the potential on the sidewall surface 942 of the microstructure 94 is switched between the second potential of −1 V and the first potential of +1 V with a switching period of 12 seconds. In Example 13, the etching amount was 22 nm.

[0114] Example 14 is similar to Example 11, except that the switching period is set to 18 seconds. In Example 14, the potential on the sidewall surface 942 of the microstructure 94 is switched between the second potential of −1 V and the first potential of +1 V with a switching period of 18 seconds. In Example 14, the etching amount was 19.5 nm.

[0115] In Comparative Example 1, as described above, the application of voltage in step S13 was omitted. In Comparative Example 1, as described above, the etching amount was 11 nm.

[0116] Comparing Examples 11 to 14 with Comparative Example 1, it can be seen that by performing step S13 (switching the applied voltage), the etching rate for the processed film 96 in the recess 95 increases even when the switching period is different.

[0117] In Examples 15 to 17 shown in Table 4, the applied voltage in step S13 was an AC voltage, and the frequency of the AC voltage was changed (i.e., the switching period was changed) to measure the etching amount of the target film 96. In Example 15, the applied voltage from the power supply unit 63 was an AC voltage, with the second voltage being −1 V and the first voltage being +1 V. The frequency of the applied voltage was 0.5 Hz (i.e., switching period: 2 seconds). That is, in Example 15, the potential on the sidewall surface 942 of the microstructure 94 (i.e., the inner surface of the recess 95) was switched between the second potential of −1 V and the first potential of +1 V with a switching period of 2 seconds. In Example 15, the etching amount was 21 nm.

[0118] Example 16 is similar to Example 15, except that the frequency is 1 Hz (switching cycle: 1 second). In Example 16, the potential on the sidewall surface 942 of the microstructure 94 is switched between the second potential of −1 V and the first potential of +1 V with a switching cycle of 1 second. In Example 16, the etching amount was 22 nm.

[0119] Example 17 is similar to Example 15, except that the frequency is 5 Hz (switching period: 0.2 seconds). In Example 17, the potential on the sidewall surface 942 of the microstructure 94 is switched between the second potential of −1 V and the first potential of +1 V with a switching period of 0.2 seconds. In Example 17, the etching amount was 16.5 nm.

[0120] In Comparative Example 1, as described above, the application of voltage in step S13 was omitted. In Comparative Example 1, as described above, the etching amount was 11 nm.

[0121] A comparison of Examples 15 to 17 with Comparative Example 1 reveals that performing step S13 (switching the applied voltage) increases the etching rate for the film to be processed 96 in the recess 95, even when the frequency of the AC voltage is different (i.e., when the switching period is different). Furthermore, a comparison of Example 15 with Example 11 (Table 3) reveals that when the first voltage, second voltage, and switching period are the same, the etching rate is approximately the same whether the applied voltage is a DC voltage or an AC voltage.

[0122] As described above, in Examples 18 to 28 and Comparative Example 3 shown in Tables 5 to 7, hydrogen peroxide solution was used as the treatment liquid. In Examples 18 to 22 shown in Table 5, the first and second voltages applied in step S13 were changed, and the etching depth of the target film 96 was measured. In Example 18, the applied voltage applied from the power supply unit 63 was a DC voltage, with the second voltage set to −1 V and the first voltage set to +1 V. The applied voltage switching cycle was 2 seconds. That is, in Example 18, the potential on the sidewall surface 942 of the microstructure 94 (i.e., the inner surface of the recess 95) was switched between the second potential of −1 V and the first potential of +1 V with a switching cycle of 2 seconds. In Example 18, the etching depth was 18 nm.

[0123] Example 19 is similar to Example 18, except that the second voltage is −2 V and the first voltage is +2 V. In Example 19, the potential on the sidewall surface 942 of the microstructure 94 is switched between the second potential of −2 V and the first potential of +2 V with a switching period of 2 seconds. In Example 19, the etching amount was 18.5 nm.

[0124] Example 20 is similar to Example 18, except that the second voltage is −3 V and the first voltage is +3 V. In Example 20, the potential on the sidewall surface 942 of the microstructure 94 is switched between the second potential of −3 V and the first potential of +3 V with a switching period of 2 seconds. In Example 20, the etching amount was 19 nm.

[0125] Example 21 is similar to Example 18, except that the second voltage is −5 V and the first voltage is +5 V. In Example 21, the potential on the sidewall surface 942 of the microstructure 94 is switched between the second potential of −5 V and the first potential of +5 V with a switching period of 2 seconds. In Example 21, the etching amount was 22.5 nm.

[0126] Example 22 is similar to Example 18, except that the second voltage is −8 V and the first voltage is +8 V. In Example 22, the potential on the sidewall surface 942 of the microstructure 94 is switched between the second potential of −8 V and the first potential of +8 V with a switching period of 2 seconds. In Example 22, the etching amount was 24.5 nm.

[0127] In Comparative Example 3, as described above, the application of voltage in step S13 was omitted. In Comparative Example 3, the etching amount was 15.5 nm.

[0128] Comparing Examples 18 to 22 with Comparative Example 3, it can be seen that by performing step S13 (switching the applied voltage), the etching rate for the processed film 96 in the recess 95 increases even when the applied voltage is different.

[0129] In Examples 23 to 25 shown in Table 6, the etching amount of the target film 96 was measured by changing the switching cycle of the applied voltage in step S13. In Example 23, the applied voltage applied from the power supply unit 63 was a DC voltage, with the second voltage being −5 V and the first voltage being +5 V. The switching cycle of the applied voltage was 0.5 seconds. That is, in Example 23, the potential on the sidewall surface 942 of the microstructure 94 (i.e., the inner surface of the recess 95) was switched between the second potential of −5 V and the first potential of +5 V with a switching cycle of 0.5 seconds. In Example 23, the etching amount was 19 nm.

[0130] Example 24 is similar to Example 23, except that the switching period is set to 1 second. In Example 24, the potential on the sidewall surface 942 of the microstructure 94 is switched between the second potential of −5 V and the first potential of +5 V with a switching period of 1 second. In Example 24, the etching amount was 21 nm.

[0131] Example 25 is similar to Example 23, except that the switching period is set to 2 seconds. In Example 25, the potential on the sidewall surface 942 of the microstructure 94 is switched between the second potential of −5 V and the first potential of +5 V with a switching period of 2 seconds. In Example 25, the etching amount was 20 nm.

[0132] In Comparative Example 3, as described above, the application of voltage in step S13 was omitted. In Comparative Example 3, as described above, the etching amount was 15.5 nm.

[0133] Comparing Examples 23 to 25 with Comparative Example 3, it can be seen that by performing step S13 (switching the applied voltage), the etching rate for the processed film 96 in the recess 95 increases even when the switching period is different.

[0134] In Examples 26 to 28 shown in Table 7, the applied voltage in step S13 was an AC voltage, and the frequency of the AC voltage was changed (i.e., the switching period was changed) to measure the etching amount of the film 96 to be processed. In Example 26, the applied voltage from the power supply unit 63 was an AC voltage, with the second voltage being −5 V and the first voltage being +5 V. The frequency of the applied voltage was 1 Hz (i.e., switching period: 1 second). That is, in Example 26, the potential on the sidewall surface 942 of the microstructure 94 (i.e., the inner surface of the recess 95) was switched between the second potential of −5 V and the first potential of +5 V with a switching period of 1 second. In Example 26, the etching amount was 20.5 nm.

[0135] Example 27 is similar to Example 26, except that the frequency is 10 Hz (switching period: 0.1 seconds). In Example 27, the potential on the sidewall surface 942 of the microstructure 94 is switched between the second potential of −5 V and the first potential of +5 V with a switching period of 0.1 seconds. In Example 27, the etching amount was 26 nm.

[0136] Example 28 is similar to Example 26, except that the frequency is 20 Hz (switching period: 0.05 seconds). In Example 28, the potential on the sidewall surface 942 of the microstructure 94 is switched between the second potential of −5 V and the first potential of +5 V with a switching period of 0.05 seconds. In Example 28, the etching amount was 17.5 nm.

[0137] In Comparative Example 3, as described above, the application of voltage in step S13 was omitted. In Comparative Example 3, as described above, the etching amount was 15.5 nm.

[0138] A comparison of Examples 26 to 28 with Comparative Example 3 reveals that performing step S13 (switching the applied voltage) increases the etching rate for the film to be processed 96 in the recess 95, even when the frequency of the AC voltage is different (i.e., when the switching period is different). Furthermore, a comparison of Example 26 with Example 24 (Table 6) reveals that when the first voltage, second voltage, and switching period are the same, the etching rate is approximately the same whether the applied voltage is a DC voltage or an AC voltage.

[0139] As described above, the substrate processing method includes a step (step S12) of supplying a conductive etching treatment liquid to a substrate 9 having a film 96 to be processed located in a recess 95 of a pattern (i.e., a fine pattern 93) and bringing the treatment liquid into contact with the film 96, and a step (step S13) of repeatedly switching a voltage applied between the substrate 9 and the treatment liquid between different first and second voltages at a predetermined switching period while the treatment liquid is in contact with the film 96 to repeatedly switch the potential of a sidewall surface 942 forming the recess 95 between a first potential and a second potential lower than the first potential. The first potential is 0 V or higher, and the second potential is 0 V or lower. The switching period is 0.05 seconds or longer.

[0140] In this way, by setting the switching period in step S13 to 0.05 seconds or more, it is possible to increase the etching rate of the target film 96, as exemplified in Examples 1 to 28. The reason for this increase in etching rate is thought to be, for example, as follows.

[0141] According to the first principle, by setting the switching period in step S13 to 0.05 seconds or more, water molecules and the like adsorbed on the surface of the film 96 to be treated in the recess 95 can be suitably electrolyzed, and the etchant, such as hydrogen peroxide, can be suitably adsorbed onto the film 96 to be treated. As a result, the etching rate of the film 96 to be treated can be increased. On the other hand, if the switching period is less than 0.05 seconds, the applied voltage is switched before the water molecules and the like adsorbed on the surface of the film 96 to be treated are sufficiently electrolyzed, resulting in insufficient electrolysis of the water molecules and the like. Therefore, the adsorption of the etchant to the film 96 to be treated is inhibited by the water molecules and the like, and the etching rate hardly increases.

[0142] Furthermore, according to the second principle, by setting the switching period in step S13 to 0.05 seconds or more, the products of etching that have increased in the recesses 95 (hereinafter also referred to as "etching products") can be suitably discharged to the outside of the recesses 95. As a result, the etchant can easily enter the recesses 95, thereby increasing the etching rate of the film 96 to be processed. On the other hand, if the switching period is less than 0.05 seconds, the applied voltage is switched before the etching products have been sufficiently discharged to the outside of the recesses 95, resulting in insufficient discharge of the etching products to the outside of the recesses 95. Therefore, the etchant is prevented from entering the recesses 95, and the etching rate does not increase much.

[0143] According to the third principle, by setting the switching period in step S13 to 0.05 seconds or more, bubbles generated in the recess 95 can be suitably discharged to the outside of the recess 95. As a result, the etchant can easily enter the recess 95, thereby increasing the etching rate of the film 96 to be processed. On the other hand, if the switching period is less than 0.05 seconds, the applied voltage is switched before the bubbles are sufficiently discharged to the outside of the recess 95, resulting in insufficient discharge of the bubbles to the outside of the recess 95. Therefore, the etchant is prevented from entering the recess 95, and the etching rate does not increase much.

[0144] According to the fourth principle, by setting the switching period in step S13 to 0.05 seconds or more, the complexes generated by etching that have increased in the recesses 95 can be suitably discharged to the outside of the recesses 95. As a result, the etchant can easily enter the recesses 95, thereby increasing the etching rate of the film 96 to be processed. On the other hand, if the switching period is less than 0.05 seconds, the applied voltage is switched before the complexes have been sufficiently discharged to the outside of the recesses 95, resulting in insufficient discharge of the complexes to the outside of the recesses 95. Therefore, the etchant is prevented from entering the recesses 95, and the etching rate does not increase much.

[0145] As described above, when the applied voltage is a DC voltage, the switching period is preferably 0.5 seconds or more, which makes it possible to suitably increase the etching rate of the film 96 to be processed.

[0146] As described above, when the applied voltage is an AC voltage, the switching period is preferably 0.2 seconds or more, which makes it possible to suitably increase the etching rate of the film 96 to be processed.

[0147] Preferably, the processing solution is an etching solution to which an electrolytic solution has been added to adjust the resistivity to 0.1 Ω·m or less. This allows the maximum and minimum values ​​of the applied voltage to be increased, thereby further increasing the etching rate of the target film 96.

[0148] Preferably, the film to be treated 96 contains one or more of TiN, TaN, TiAl, and TiAlC, and the treatment liquid is H ２ O ２ This makes it possible to suitably increase the etching rate of the target film 96 by the above-described substrate processing method.

[0149] In the above substrate processing method, bubbles generated during etching can be effectively discharged outside the recess 95, and therefore the substrate processing method is particularly suitable for cases where bubbles are generated within the recess 95 in step S13.

[0150] The substrate processing method described above can increase the etching rate of the target film 96 present in a narrow recess 95, which would otherwise be etched at a lower rate in conventional processing methods. Therefore, the substrate processing method is particularly suitable for etching a substrate 9 having a recess 95 with a width of 10 nm or less.

[0151] The substrate processing apparatus 1 includes a substrate holding unit 31 for holding a substrate 9, a processing liquid supply unit 5 for supplying a conductive etching processing liquid to the substrate 9 and bringing it into contact with a film 96 to be processed, a first electrode 61 electrically connected to the substrate 9, a second electrode 62 electrically connected to the processing liquid, a power supply unit 63 for applying a voltage between the first electrode 61 and the second electrode 62, and a power supply control unit 81 for controlling the power supply unit 63 to repeatedly switch the applied voltage between different first and second voltages at a predetermined switching period while the processing liquid is in contact with the film 96 to repeatedly switch the potential of a sidewall surface 942 forming a recess 95 between a first potential and a second potential lower than the first potential. The first potential is 0 V or higher, and the second potential is 0 V or lower. The switching period is 0.05 seconds or longer. This increases the etching rate of the film 96 to be processed, as described above.

[0152] Considering the second to fourth principles described above, as etching of the film to be processed 96 progresses and the distance between the film to be processed 96 in the recess 95 and the opening of the recess 95 (i.e., the distance between the end face 941 of the microstructure 94) increases, it becomes more difficult for etching products, bubbles, complexes, etc. in the recess 95 (particularly those present far from the opening of the recess 95) to be discharged to the outside of the recess 95. Therefore, the time required to discharge the etching products, bubbles, and / or complexes, etc. from the recess 95 increases. Therefore, in the above-described substrate processing method, it is preferable to increase the time for applying the voltage for discharging the etching products, bubbles, and / or complexes, etc. as etching progresses.

[0153] That is, in the above-described substrate processing method, it is preferable to increase the switching period as the elapsed time from the start of step S13 increases. Furthermore, in the substrate processing apparatus 1, it is preferable that the power supply control unit 81 increase the switching period as the elapsed time from the start of switching the applied voltage increases. This makes it possible to prevent a decrease in the etching rate even when the distance from the opening of the recess 95 to the target film 96 increases as etching progresses. Note that the above-described preferred range of the switching period is a preferred switching period when the switching period is not changed in step S13. When the switching period is increased as the elapsed time from the start of switching the applied voltage increases, the preferred range may change as the elapsed time increases.

[0154] Furthermore, in order to suitably discharge etching products, bubbles, and / or complexes, which become difficult to discharge as etching progresses, from recess 95, it is also preferable to increase the flow rate of the processing liquid supplied to recess 95. That is, in the above-described substrate processing method, it is preferable that processing liquid is continuously supplied to substrate 9 in step S12, and the supply flow rate of the processing liquid is increased as the elapsed time from the start of step S13 increases. This makes it possible to suppress a decrease in the etching rate even if the distance from the opening of recess 95 to film 96 to be processed increases as etching progresses.

[0155] Preferably, the substrate processing apparatus 1 further includes a supply control unit 82 that controls the processing liquid supply unit 5. The processing liquid is continuously supplied to the substrate 9 while the power supply control unit 81 repeatedly switches the applied voltage, and the supply control unit 82 preferably increases the supply flow rate of the processing liquid from the processing liquid supply unit 5 as the elapsed time from the start of switching the applied voltage increases. This makes it possible to prevent a decrease in the etching rate even when the distance from the opening of the recess 95 to the processing target film 96 increases as etching progresses.

[0156] Considering the first principle described above, as shown in Fig. 6C, when a negative voltage is applied to the first electrode 61, electrolysis of water molecules 72 occurs, but this does not promote adsorption of hydrogen peroxide molecules 71 (i.e., the etchant) to the film to be treated 96, and therefore etching is not substantially promoted. Therefore, it is preferable to prolong the state in which a positive voltage is applied to the first electrode 61 and adsorption of the etchant is promoted, as shown in Fig. 6D, rather than the state in Fig. 6C.

[0157] That is, in the substrate processing method, in each switching period, the application time of the first voltage corresponding to the first potential (i.e., the first application time T Ｄｐ , T Ａｐ ) is the application time of the second voltage corresponding to the second potential (i.e., the second application time T Ｄｍ , T Ａｍ ) is preferably longer than the time during which the processing target film 96 is etched in each switching period. This makes it possible to lengthen the time during which the processing target film 96 is etched in each switching period, thereby increasing the etching rate.

[0158] First application time T Ｄｐ , T Ａｐ is the second application time T Ｄｍ , T Ａｍ The first application time T Ｄｐ , T Ａｐ is the second application time T Ｄｍ , T Ａｍ For example, it is 5 times or less, and preferably 4 times or less.

[0159] Table 8 shows Examples 29 and 30, which show the relationship between the first application time and the second application time and the etching amount.

[0160]

[0161] In Examples 29 and 30, the above-described test pieces were subjected to the processes corresponding to steps S11 to S15, and the etching depth after the processes was measured in the same manner as described above. In step S12, a mixture of hydrogen peroxide solution with a concentration of 30% to 35% by mass, hydrochloric acid solution with a concentration of 35% to 37% by mass, and deionized water (DIW) was used as the treatment liquid. The volume ratio of hydrogen peroxide solution, hydrochloric acid solution, and deionized water in the treatment liquid was 1:1:8. The temperature of the treatment liquid when supplied to the substrate 9 was 50°C. The applied voltage in step S13 was a DC voltage as illustrated in FIG. 5A, and the first and second voltages were +8 V and −8 V, respectively. The treatment time in steps S12 and S13 (i.e., the time during which the treatment liquid was supplied to the substrate 9 while the applied voltage was being applied) was 16 minutes.

[0162] In the etching amount column, the recess width of 2 nm and the recess width of 4 nm indicate that the etching amounts listed in the lower part of the column are those when the width D2 of the recess 95 in the width direction (i.e., the vertical direction in Figure 9) is 2 nm and 4 nm, respectively.

[0163] In Example 29, the power supply unit 63 was controlled so that the first and second application times in the switching cycle of the applied voltage were 3 seconds and 1 second, respectively. That is, the first application time was three times longer than the second application time. In Example 29, the etching depth was 24 nm when the recess width was 2 nm, and 23 nm when the recess width was 4 nm.

[0164] In Example 30, the power supply unit 63 was controlled so that the first application time and the second application time in each switching cycle of the applied voltage were each 3 seconds. That is, the first application time was the same as the second application time. In Example 30, the etching depth was 17 nm when the recess width was 2 nm, and 16 nm when the recess width was 4 nm.

[0165] It can be seen that by making the first application time longer than the second application time as in Example 29, the etching rate increases compared to when the first application time and the second application time are the same as in Example 30.

[0166] The substrate processing method and substrate processing apparatus 1 described above can be modified in various ways.

[0167] For example, the film 96 to be etched using the above-mentioned substrate processing method does not necessarily have to be located within a recess 95 in the fine pattern 93 that is 10 nm or less in width, but may be located within a recess 95 in the fine pattern 93 that has a width greater than 10 nm.

[0168] In each switching cycle of the applied voltage, the first application time may be the same as or longer than the second application time as described above, or may be shorter than the second application time.

[0169] The material of the film 96 to be processed is not limited to the above and may be variously changed. For example, the film 96 to be processed may be a semiconductor film made of a semiconductor, or an insulating film made of an insulator. The film 96 to be processed may be a semiconductor film such as a polysilicon film or an amorphous silicon film. Alternatively, the film 96 to be processed may be a semiconductor film such as a silicon oxide film or a silicon nitride film.

[0170] The processing liquid used in the above etching is not necessarily H ２ O ２ The resistivity of the treatment solution may be higher than 0.1 Ω·m, as described above. The treatment solution may contain an etchant, and does not necessarily need to contain an electrolyte.

[0171] When etching the film 96 to be processed, bubbles are not necessarily generated in the recess 95 as in the third principle, and bubbles do not necessarily have to be generated.

[0172] The first electrode 61 does not necessarily need to be electrically connected to the substrate 9 via the substrate holding part 31, and may be electrically connected to the substrate 9 via a structure other than the substrate holding part 31. Alternatively, the first electrode 61 may be electrically connected to the substrate 9 by directly contacting the lower surface 92 of the substrate 9, etc.

[0173] The second electrode 62 does not necessarily need to be electrically connected to the processing liquid via the nozzle 51, and may be electrically connected to the processing liquid via a structure other than the nozzle 51 (for example, a pipe that supplies the processing liquid to the nozzle 51). Alternatively, the second electrode 62 may be electrically connected to the processing liquid by directly contacting the processing liquid located on the upper surface 91 of the substrate 9.

[0174] The substrate processing apparatus 1 does not necessarily have to be a single-wafer type apparatus that processes the substrates 9 one by one, but may be a batch type apparatus that simultaneously etch a plurality of substrates 9 .

[0175] The substrate processing apparatus 1 may be used to process glass substrates used in flat panel displays such as liquid crystal displays or organic electroluminescence (EL) displays, or glass substrates used in other displays, in addition to semiconductor substrates. The substrate processing apparatus 1 may also be used to process substrates for optical disks, magnetic disks, magneto-optical disks, photomasks, ceramic substrates, and solar cell substrates.

[0176] The configurations in the above-described embodiment and each modification may be combined as appropriate as long as they are not mutually contradictory.

[0177] While the invention has been particularly illustrated and described, it should be understood that the foregoing description is illustrative and not restrictive, and that numerous modifications and variations are possible without departing from the scope of the invention.

[0178] REFERENCE SIGNS LIST 1 substrate processing apparatus 5 processing liquid supply unit 9 substrate 31 substrate holder 61 first electrode 62 second electrode 63 power supply unit 81 power supply control unit 82 supply control unit 93 fine pattern 95 recess 96 processing target film 942 sidewall surface S11 to S15 steps

Claims

1. A substrate processing method for etching a substrate having a film to be processed located in a recess of a pattern, comprising: a) a step of supplying an etching processing liquid having conductivity to the substrate and bringing it into contact with the film to be processed; and b) a step of repeatedly switching an applied voltage between the substrate and the processing liquid, while the processing liquid is in contact with the film to be processed, between a first voltage and a second voltage that are different from each other, at a predetermined switching period, thereby repeatedly switching the potential of the sidewall surface forming the recess between a first potential and a second potential that is smaller than the first potential, wherein the first potential is 0 V or more, the second potential is 0 V or less, and the switching period is 0.05 seconds or more.

2. A substrate processing method according to claim 1, wherein the applied voltage is a DC voltage, and the switching period is 0.5 seconds or longer.

3. A substrate processing method according to claim 1, wherein the applied voltage is an AC voltage, and the switching period is 0.2 seconds or longer.

4. A substrate processing method according to claim 1, wherein, in each switching period, the application time of the first voltage corresponding to the first potential is longer than the application time of the second voltage corresponding to the second potential.

5. A substrate processing method according to claim 1, wherein the processing liquid is an etching liquid to which an electrolytic solution has been added, the resistivity of which is set to 0.1 Ω·m or less.

6. A substrate processing method according to claim 1, wherein the film to be processed contains one or more of TiN, TaN, TiAl, and TiAlC, and the processing liquid is H ２ O ２ A substrate processing method comprising:

7. A substrate processing method according to claim 1, wherein the switching period is increased as the elapsed time from the start of step b) increases.

8. A substrate processing method according to claim 1, wherein in step a), the processing liquid is continuously supplied to the substrate, and the supply flow rate of the processing liquid is increased as the elapsed time from the start of step b) increases.

9. A substrate processing method according to claim 1, wherein in step b), bubbles are generated in the recess.

10. A substrate processing method according to any one of claims 1 to 9, wherein the width of the recess is 10 nm or less.

11. A substrate processing apparatus for etching a substrate having a film to be processed located in a recess of a pattern, comprising: a substrate holding unit for holding the substrate; a processing liquid supply unit for supplying a conductive etching processing liquid to the substrate and bringing it into contact with the film to be processed; a first electrode electrically connected to the substrate; a second electrode electrically connected to the processing liquid; a power supply unit for applying an applied voltage between the first electrode and the second electrode; and a power supply control unit for controlling the power supply unit to repeatedly switch the applied voltage between a first voltage and a second voltage that are different from each other at a predetermined switching period while the processing liquid is in contact with the film to be processed, thereby repeatedly switching the potential of a sidewall surface forming the recess between a first potential and a second potential that is smaller than the first potential, wherein the first potential is 0 V or more, and the second potential is 0 V or less, and the switching period is 0.05 seconds or more.

12. A substrate processing apparatus according to claim 11, wherein the applied voltage is a DC voltage, and the switching period is 0.5 seconds or longer.

13. A substrate processing apparatus according to claim 11, wherein the applied voltage is an AC voltage, and the switching period is 0.2 seconds or longer.

14. A substrate processing apparatus according to claim 11, wherein, in each switching period, the application time of the first voltage corresponding to the first potential is longer than the application time of the second voltage corresponding to the second potential.

15. A substrate processing apparatus according to claim 11, wherein the processing liquid is an etching liquid to which an electrolytic solution has been added, and the resistivity of the processing liquid is adjusted to 0.1 Ω·m or less.

16. A substrate processing apparatus according to claim 11, wherein the film to be processed contains one or more of TiN, TaN, TiAl, and TiAlC, and the processing liquid is H ２ O ２ A substrate processing apparatus comprising:

17. A substrate processing apparatus according to claim 11, wherein the power supply control unit increases the switching cycle as the time elapsed since the start of switching of the applied voltage increases.

18. A substrate processing apparatus according to claim 11, further comprising a supply control unit that controls the processing liquid supply unit, wherein the processing liquid is continuously supplied to the substrate while the power supply control unit repeatedly switches the applied voltage, and the supply control unit increases the supply flow rate of the processing liquid from the processing liquid supply unit as the elapsed time from the start of switching the applied voltage becomes longer.

19. The substrate processing apparatus according to claim 11, wherein bubbles are generated in the recess while the power supply control unit repeatedly switches the applied voltage.

20. A substrate processing apparatus according to any one of claims 11 to 19, wherein the width of the recess is 10 nm or less.

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