Substrate processing method and substrate processing apparatus

Abstract

To intentionally etch a side surface of a recess formed in a substrate non-uniformly while suppressing an increase in a processing time.SOLUTION: A recess 95 is formed in a substrate W. A width of the recess 95 is shorter than a depth of the recess 95. An etching target representing at least one of a single crystal of silicon, polysilicon, and amorphous silicon is exposed at at least a part of an upper part of a side surface 95s and at least a part of a lower part of the side surface 95s. An alkaline first etching liquid prepared by diluting an etching stock solution with a first diluent having a first dissolved oxygen concentration stored in a first diluent tank is supplied to the substrate W. An alkaline second etching liquid prepared by diluting the etching stock solution with a second diluent having a second dissolved oxygen concentration higher than the first dissolved oxygen concentration stored in a second diluent tank is supplied to the substrate W before or after the first etching liquid is supplied to the substrate W.SELECTED DRAWING: Figure 9A-C

Description

[Technical Field]

[0001] The present invention relates to a substrate processing method and a substrate processing apparatus for processing substrates, including, for example, semiconductor wafers, substrates for FPDs (Flat Panel Displays) such as liquid crystal displays and organic EL (electroluminescence) displays, substrates for optical disks, substrates for magnetic disks, substrates for magneto-optical disks, substrates for photomasks, ceramic substrates, and substrates for solar cells. [Background technology]

[0002] In the manufacturing process of semiconductor devices and FPDs, an alkaline etching solution such as TMAH (tetramethyl ammonium hydroxide) or KOH (potassium hydroxide) is sometimes supplied to a substrate such as a semiconductor wafer or a glass substrate for an FPD. Patent Document 1 discloses that a polysilicon film formed on a substrate is etched by supplying TMAH to the substrate. It describes that the dissolved oxygen concentration in TMAH is adjusted to an optimum concentration by dissolving nitrogen gas or dry air in the TMAH. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-19089 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 discloses etching a polysilicon film formed on the outermost layer of a substrate by supplying TMAH, but does not disclose whether a pattern is formed on the outermost layer of the substrate. In addition, Patent Document 1 discloses supplying TMAH to multiple substrates while changing the dissolved oxygen concentration of the TMAH, but does not disclose supplying TMAH with different dissolved oxygen concentrations to the same substrate.

[0005] In the manufacturing process of semiconductor devices and the like, an alkaline etching solution such as TMAH is sometimes supplied to the surface of a substrate on which a pattern such as a recess is formed, to etch the side of the recess. In such cases, rather than uniformly etching the side of the recess, it is sometimes required to intentionally etch the side of the recess non-uniformly. This requirement usually includes suppressing an increase in processing time. Patent Document 1 does not disclose or suggest a method or apparatus that meets this requirement.

[0006] Therefore, one object of the present invention is to provide a substrate processing method and a substrate processing apparatus that can intentionally etch the side surfaces of a recess formed in a substrate non-uniformly while suppressing an increase in processing time. [Means for solving the problem]

[0007] One embodiment of the present invention provides a substrate processing method for processing a substrate having a recess formed thereon, the recess having a width smaller than a depth, and an etching object representing at least one of single crystal silicon, polysilicon, and amorphous silicon exposed at at least a portion of an upper part of a side surface and at least a portion of a lower part of the side surface, the substrate processing method including: a first etching step of supplying to the substrate a first alkaline etching liquid containing dissolved inert gas, thereby etching the etching object exposed at the side surface of the recess; and a second etching step of supplying to the substrate a second alkaline etching liquid containing dissolved gas and having a higher dissolved oxygen concentration than the first etching liquid, thereby etching the etching object exposed at the side surface of the recess.

[0008] In this method, a first alkaline etching solution containing an inert gas dissolved therein is supplied to the substrate. This etches the side surfaces of the recesses formed in the substrate. Similarly, a second alkaline etching solution containing an inert gas dissolved therein is supplied to the substrate. This etches the side surfaces of the recesses. Thus, the side surfaces of the recesses are etched in stages by the supply of the first etching solution and the supply of the second etching solution.

[0009] The etching target, which represents at least one of single crystal silicon, polysilicon, and amorphous silicon, is exposed at least part of the upper portion of the side surface of the recess and at least part of the lower portion of the side surface of the recess. When a liquid with a high concentration of dissolved oxygen is supplied to the etching target, the surface layer of the etching target is converted to silicon oxide. Silicon oxide is not etched, or is barely etched, by the alkaline etching solution.

[0010] The dissolved oxygen present in the first etching solution is removed from the first etching solution by dissolving the inert gas. Since the dissolved oxygen concentration in the first etching solution is low, even when the first etching solution comes into contact with the object to be etched, the object is not oxidized or is hardly oxidized. Therefore, by supplying the first etching solution to the substrate, the object to be etched exposed on the side surface of the recess can be etched uniformly at a high etching rate.

[0011] On the other hand, because the dissolved oxygen concentration in the second etching solution is higher than that in the first etching solution, when the second etching solution comes into contact with the etching target, the surface layer of the etching target is oxidized and converted into silicon oxide, which is resistant to corrosion by the second etching solution. However, the surface layer of the etching target is not oxidized uniformly across the entire surface, but is oxidized unevenly. That is, because the width of the recess is narrow, when the second etching solution is supplied to the recess, the dissolved oxygen contained in the second etching solution comes into contact with the etching target near the entrance of the recess and oxidizes the etching target. Therefore, the second etching solution with a reduced dissolved oxygen concentration flows toward the bottom of the recess, albeit slightly. Even at a distance from the entrance of the recess, the dissolved oxygen in the second etching solution comes into contact with the etching target and is consumed. As a result of this phenomenon being continuously repeated, the dissolved oxygen concentration in the second etching solution decreases as it approaches the bottom of the recess.

[0012] If the depth of the recess is the same, the etching target is uniformly etched by the second etching liquid. However, the etching amount of the etching target increases as one approaches the bottom of the recess. That is, near the entrance of the recess, the surface layer of the etching target has changed to silicon oxide, so the etching target is difficult to etch by the second etching liquid. On the other hand, near the bottom of the recess, the surface layer of the etching target has not changed to silicon oxide or has changed very little, so the etching target is etched by the second etching liquid. Therefore, the etching amount of the etching target near the bottom of the recess is greater than the etching amount of the etching target near the entrance of the recess.

[0013] In this way, by supplying the first etching liquid to the substrate, the etching target exposed on the side surface of the recess can be etched uniformly at a high etching rate. Furthermore, by supplying the second etching liquid to the substrate, the etching target can be etched so that the etching amount increases stepwise or continuously as the etching target approaches the bottom of the recess. Therefore, by supplying the first etching liquid and the second etching liquid separately to the substrate, the side surface of the recess can be intentionally etched non-uniformly while suppressing an increase in processing time.

[0014] The recess formed in the substrate may be a hole or a groove. That is, the side surface of the recess may be a cylindrical surface that is continuous around the entire circumference, or one or both of a pair of parallel opposing side surfaces. The recess may be recessed in the thickness direction of the substrate, or in a surface direction of the substrate that is perpendicular to the thickness direction of the substrate. In the former case, the recess may be recessed from the outermost surface of the substrate in the thickness direction of the substrate, or may be recessed from another plane in the thickness direction of the substrate.

[0015] The first etching solution is an alkaline etching solution in which an inert gas is forcibly dissolved, and the second etching solution is an alkaline etching solution in which a dissolved gas is forcibly dissolved. As long as the dissolved oxygen concentration of the second etching solution is higher than that of the first etching solution, the dissolved gas may be an inert gas such as nitrogen gas or argon gas, or an oxygen-containing gas.

[0016] In the above embodiment, at least one of the following features may be added to the substrate processing method. The second etching step is a step of supplying the second etching liquid to the substrate after the first etching liquid has been supplied to the substrate. In this method, a first etching liquid with a low dissolved oxygen concentration is supplied to the substrate, followed by a second etching liquid with a relatively high dissolved oxygen concentration. If the second etching liquid is supplied to the substrate first, the etching target exposed on the side of the recess is oxidized. Therefore, when the first etching liquid is supplied, the etching target is etched unevenly or the etching rate is reduced. By supplying the first etching liquid first, the processing time can be shortened compared to when the second etching liquid is supplied first, and the actual shape of the etched etching target can be closer to the intended shape.

[0017] The second etching step includes a step of supplying the second etching liquid to the substrate, thereby replacing the first etching liquid in contact with the substrate with the second etching liquid. In this method, after the first etching liquid is supplied to the substrate, the second etching liquid is supplied to the substrate, rather than supplying any liquid other than the second etching liquid to the substrate. This replaces the first etching liquid in contact with the substrate with the second etching liquid. If a liquid other than the second etching liquid is supplied to the substrate before the second etching liquid is supplied, the etching target exposed on the side of the recess may be unintentionally oxidized. By replacing the first etching liquid in contact with the substrate with the second etching liquid, such oxidation can be suppressed or prevented, allowing the etching target to be etched accurately.

[0018] The width of the recess before the first etching liquid and the second etching liquid are supplied decreases as the recess approaches the bottom, and the second etching step is a step of etching the side surface of the recess so that the amount of etching of the side surface of the recess increases as the recess approaches the bottom.

[0019] In this method, a recess that narrows toward the bottom of the recess is etched with a first etching liquid and a second etching liquid. When the first etching liquid is supplied, the material to be etched exposed on the side of the recess is uniformly etched, and when the second etching liquid is supplied, the amount of material etched increases toward the bottom of the recess. After the first etching liquid and the second etching liquid are supplied, the width of the recess becomes uniform from the entrance to the bottom of the recess, or the unevenness of the width of the recess is reduced. Therefore, if the width of the recess before etching is uneven, the shape of the recess can be adjusted.

[0020] At least one of the first etching liquid and the second etching liquid is an alkaline etching liquid containing a compound that inhibits contact between hydroxide ions and the object to be etched. Polysilicon is composed of many single crystals of silicon. When polysilicon is etched with an alkaline etching solution that does not contain any compounds, extremely fine irregularities are formed on the surface of the polysilicon. This is because the (110), (100), and (111) faces of silicon are exposed on the surface of the polysilicon, and the etching rates of the (110), (100), and (111) faces of silicon are different from one another. When single crystal silicon is etched, extremely fine irregularities are formed on the surface of the single crystal silicon for the same reason.

[0021] Hydroxide ions (OH) in alkaline etching solutions - ) reacts with silicon (Si) and etches materials such as polysilicon. When the compound is added to an alkaline etching solution, it inhibits contact between hydroxide ions and silicon, slowing down the etching rates of the (110), (100), and (111) silicon faces. However, the etching rate does not decrease uniformly across multiple crystal faces; rather, it decreases more significantly for the crystal faces with the highest etching rates. This reduces the difference in etching rate across multiple crystal faces.

[0022] In this way, by adding a compound to an alkaline etching solution, the anisotropy of the etching solution with respect to the etching target, such as polysilicon, is reduced. In other words, the etching of the etching target approaches isotropic etching, and the etching target is etched at a uniform etching amount at every location. This reduces the dependence of the etching rate on the surface orientation. Therefore, the occurrence of the above-mentioned unevenness can be suppressed or prevented, and the surface of the etching target can be flattened after etching.

[0023] The concentration of the compound in the alkaline etching solution is set depending on the required etching uniformity and the required etching rate. The first etching step includes a first etching solution preparation step of preparing the first etching solution by diluting an alkaline etching solution stock solution with at least one of a first dilution solution and a second dilution solution having different dissolved oxygen concentrations, and the second etching step includes a second etching solution preparation step of preparing the second etching solution by diluting the stock solution with at least one of the first dilution solution and the second dilution solution.

[0024] According to this method, a first etching solution and a second etching solution can be prepared by diluting an alkaline etching solution stock solution with at least one of a first diluent and a second diluent. The first diluent and the second diluent are liquids with different dissolved oxygen concentrations. Therefore, by making the ratio of the first diluent and the second diluent contained in the first etching solution different from the ratio of the first diluent and the second diluent contained in the second etching solution, the dissolved oxygen concentrations of the first etching solution and the second etching solution can be adjusted.

[0025] In the substrate processing method, the plurality of substrates are processed one by one. In the substrate processing method, a plurality of the substrates are processed at once. Another embodiment of the present invention provides a substrate processing apparatus for processing a substrate having a recess in which an etching target, the recess having a width smaller than a depth and representing at least one of single crystal silicon, polysilicon, and amorphous silicon, is exposed at at least a portion of an upper part of a side surface and at least a portion of a lower part of the side surface, the substrate processing apparatus including: a first etching means for supplying to the substrate a first alkaline etching solution containing dissolved in an inert gas, thereby etching the etching target exposed at the side surface of the recess; and a second etching means for supplying to the substrate a second alkaline etching solution containing dissolved gas and having a higher dissolved oxygen concentration than the first etching solution, thereby etching the etching target exposed at the side surface of the recess. This configuration can achieve the same effects as the above-mentioned substrate processing method. [Brief explanation of the drawings]

[0026] [Figure 1A] 1 is a schematic diagram showing a substrate processing apparatus according to a first embodiment of the present invention as viewed from above. [Figure 1B] FIG. 2 is a schematic side view of the substrate processing apparatus. [Figure 2] 1 is a horizontal schematic view of the interior of a processing unit provided in a substrate processing apparatus. FIG. [Figure 3] FIG. 3 is an enlarged view of a part of FIG. 2. [Figure 4] 1 is a graph showing an example of the relationship between the etching rate of three crystal planes of silicon and the concentration of propylene glycol in the etching solution. [Figure 5A] FIG. 1 is a diagram for explaining a mechanism assumed when contact between hydroxide ions and polysilicon is inhibited by an inhibitor. [Figure 5B] FIG. 1 is a diagram for explaining a mechanism assumed when contact between hydroxide ions and polysilicon is inhibited by an inhibitor. [Figure 6] 1 is a schematic view showing a processing liquid supply unit of a substrate processing apparatus that supplies a processing liquid such as an etching liquid to a substrate. [Figure 7] FIG. 2 is a block diagram showing an electrical configuration of the substrate processing apparatus. [Figure 8] 5A to 5C are process diagrams for explaining an example of substrate processing performed by the substrate processing apparatus. [Figure 9A-C] FIG. 2 is a schematic diagram showing an example of a cross section of a substrate. [Figure 10A] FIG. 10 is a schematic diagram showing another example of a cross section of a substrate. [Figure 10B] FIG. 10 is a schematic diagram showing another example of a cross section of a substrate. [Figure 10C] FIG. 10 is a schematic diagram showing another example of a cross section of a substrate. [Figure 11] FIG. 10 is a schematic view showing an etching unit provided in a substrate processing apparatus according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Fig. 1A is a schematic diagram showing a substrate processing apparatus 1 according to a first embodiment of the present invention as viewed from above, and Fig. 1B is a schematic diagram showing the substrate processing apparatus 1 as viewed from the side. 1A, the substrate processing apparatus 1 is a single-wafer processing apparatus that processes disk-shaped substrates W such as semiconductor wafers one by one. The substrate processing apparatus 1 includes a load port LP that holds a carrier C that accommodates a substrate W, a plurality of processing units 2 that process the substrates W transferred from the carrier C on the load port LP, a transfer robot that transfers the substrates W between the carrier C on the load port LP and the processing units 2, and a control device 3 that controls the substrate processing apparatus 1.

[0028] The transport robots include an indexer robot IR that loads and unloads substrates W into and from carriers C on the load port LP, and a center robot CR that loads and unloads substrates W into and from multiple processing units 2. The indexer robot IR transports substrates W between the load port LP and the center robot CR, and the center robot CR transports substrates W between the indexer robot IR and the processing units 2. The center robot CR includes a hand H1 that supports the substrate W, and the indexer robot IR includes a hand H2 that supports the substrate W.

[0029] The processing units 2 form multiple towers TW arranged around a center robot CR in a plan view. FIG. 1A shows an example in which four towers TW are formed. The center robot CR can access any of the towers TW. As shown in FIG. 1B, each tower TW includes multiple (e.g., three) processing units 2 stacked one on top of the other.

[0030] Fig. 2 is a horizontal schematic diagram of the interior of a processing unit 2 provided in the substrate processing apparatus 1. Fig. 3 is an enlarged view of a portion of Fig. 2. Fig. 2 shows a state in which the lifting frame 32 and the blocking member 33 are in a lower position, and Fig. 3 shows a state in which the lifting frame 32 and the blocking member 33 are in an upper position. In the following description, TMAH means an aqueous solution of TMAH unless otherwise specified.

[0031] The processing unit 2 includes a box-shaped chamber 4 having an internal space, a spin chuck 10 that holds one substrate W horizontally within the chamber 4 and rotates the substrate W around a vertical rotation axis A1 that passes through the center of the substrate W, and a cylindrical processing cup 23 that surrounds the spin chuck 10 around the rotation axis A1. The chamber 4 includes a box-shaped partition 6 having an inlet / outlet port 6b through which the substrate W passes, and a shutter 7 for opening and closing the inlet / outlet port 6b. The chamber 4 further includes a rectifying plate 8 disposed below an air outlet 6a that opens in the ceiling surface of the partition 6. An FFU 5 (fan filter unit) that supplies clean air (air filtered by a filter) is disposed above the air outlet 6a. An exhaust duct 9 that exhausts gas from the chamber 4 is connected to the processing cup 23. The air outlet 6a is disposed at the upper end of the chamber 4, and the exhaust duct 9 is disposed at the lower end of the chamber 4. A portion of the exhaust duct 9 is disposed outside the chamber 4.

[0032] The rectifying plate 8 divides the internal space of the partition wall 6 into an upper space Su above the rectifying plate 8 and a lower space SL below the rectifying plate 8. The upper space Su between the ceiling surface of the partition wall 6 and the upper surface of the rectifying plate 8 is a diffusion space in which clean air diffuses. The lower space SL between the lower surface of the rectifying plate 8 and the floor surface of the partition wall 6 is a processing space in which processing of the substrate W is performed. The spin chuck 10 and the processing cup 23 are disposed in the lower space SL. The vertical distance from the floor surface of the partition wall 6 to the lower surface of the rectifying plate 8 is longer than the vertical distance from the upper surface of the rectifying plate 8 to the ceiling surface of the partition wall 6.

[0033] The FFU 5 sends clean air to the upper space Su through the air outlet 6a. The clean air supplied to the upper space Su hits the rectifying plate 8 and diffuses in the upper space Su. The clean air in the upper space Su passes through a plurality of through-holes that penetrate the rectifying plate 8 from top to bottom, and flows downward from the entire area of ​​the rectifying plate 8. The clean air supplied to the lower space SL is sucked into the processing cup 23 and discharged from the lower end of the chamber 4 through the exhaust duct 9. As a result, a uniform downward flow of clean air flowing downward from the rectifying plate 8 is formed in the lower space SL. The processing of the substrate W is performed with the downward flow of clean air being formed.

[0034] The spin chuck 10 includes a disk-shaped spin base 12 held in a horizontal position, a plurality of chuck pins 11 that hold the substrate W in a horizontal position above the spin base 12, a spin shaft 13 extending downward from the center of the spin base 12, and a spin motor 14 that rotates the spin shaft 13 to rotate the spin base 12 and the plurality of chuck pins 11. The spin chuck 10 is not limited to a clamping type chuck that brings the plurality of chuck pins 11 into contact with the outer peripheral surface of the substrate W, but may also be a vacuum type chuck that holds the substrate W horizontally by adsorbing the back surface (lower surface) of the substrate W, which is the surface on which devices are not formed, to the upper surface 12u of the spin base 12.

[0035] The spin base 12 includes an upper surface 12u disposed below the substrate W. The upper surface 12u of the spin base 12 is parallel to the lower surface of the substrate W. The upper surface 12u of the spin base 12 is an opposing surface facing the lower surface of the substrate W. The upper surface 12u of the spin base 12 is annular and surrounds the rotation axis A1. The outer diameter of the upper surface 12u of the spin base 12 is larger than the outer diameter of the substrate W. The chuck pins 11 protrude upward from the outer periphery of the upper surface 12u of the spin base 12. The chuck pins 11 are held by the spin base 12. The substrate W is held by the multiple chuck pins 11 with the lower surface of the substrate W spaced apart from the upper surface 12u of the spin base 12.

[0036] The processing unit 2 includes a lower surface nozzle 15 that discharges a processing liquid toward the center of the lower surface of the substrate W. The lower surface nozzle 15 includes a nozzle disk portion disposed between the upper surface 12u of the spin base 12 and the lower surface of the substrate W, and a nozzle cylinder portion extending downward from the nozzle disk portion. A liquid discharge port 15p of the lower surface nozzle 15 opens at the center of the upper surface of the nozzle disk portion. When the substrate W is held by the spin chuck 10, the liquid discharge port 15p of the lower surface nozzle 15 faces the center of the lower surface of the substrate W in the vertical direction.

[0037] The substrate processing apparatus 1 includes a lower rinse liquid pipe 16 that guides the rinse liquid to the lower surface nozzle 15, and a lower rinse liquid valve 17 that is disposed in the lower rinse liquid pipe 16. When the lower rinse liquid valve 17 is opened, the rinse liquid guided by the lower rinse liquid pipe 16 is discharged upward from the lower surface nozzle 15 and supplied to the central portion of the lower surface of the substrate W. The rinse liquid supplied to the lower surface nozzle 15 is pure water (deionized water: DIW). The rinse liquid supplied to the lower surface nozzle 15 is not limited to pure water, and may be any of IPA (isopropyl alcohol), carbonated water, electrolytic ionized water, hydrogen water, ozone water, and hydrochloric acid water with a diluted concentration (for example, about 1 to 100 ppm).

[0038] Although not shown, the lower rinse liquid valve 17 includes a valve body having an internal flow path through which the liquid flows and an annular valve seat surrounding the internal flow path, a valve element movable relative to the valve seat, and an actuator that moves the valve element between a closed position where the valve element contacts the valve seat and an open position where the valve element is spaced from the valve seat. The same applies to the other valves. The actuator may be a pneumatic actuator, an electric actuator, or another type of actuator. The control device 3 controls the actuator to open and close the lower rinse liquid valve 17.

[0039] The outer peripheral surface of the lower nozzle 15 and the inner peripheral surface of the spin base 12 form a lower cylindrical passage 19 that extends vertically. The lower cylindrical passage 19 includes a lower central opening 18 that opens at the center of the upper surface 12u of the spin base 12. The lower central opening 18 is disposed below the nozzle disk portion of the lower nozzle 15. The substrate processing apparatus 1 includes a lower gas pipe 20 that guides the inert gas supplied to the lower central opening 18 via the lower cylindrical passage 19, a lower gas valve 21 that is interposed in the lower gas pipe 20, and a lower gas flow rate adjustment valve 22 that changes the flow rate of the inert gas supplied from the lower gas pipe 20 to the lower cylindrical passage 19.

[0040] The inert gas supplied from the lower gas pipe 20 to the lower cylindrical passage 19 is nitrogen gas. The inert gas is not limited to nitrogen gas, and may be other inert gases such as helium gas or argon gas. These inert gases are low-oxygen gases having an oxygen concentration lower than the oxygen concentration in air (approximately 21 vol%). When the lower gas valve 21 is opened, nitrogen gas supplied from the lower gas pipe 20 to the lower cylindrical passage 19 is discharged upward from the lower central opening 18 at a flow rate corresponding to the aperture of the lower gas flow rate adjustment valve 22. The nitrogen gas then flows radially in all directions through the space between the lower surface of the substrate W and the upper surface 12u of the spin base 12. This fills the space between the substrate W and the spin base 12 with nitrogen gas, reducing the oxygen concentration in the atmosphere. The oxygen concentration in the space between the substrate W and the spin base 12 is changed according to the aperture of the lower gas valve 21 and the lower gas flow rate adjustment valve 22. The lower gas valve 21 and the lower gas flow rate adjustment valve 22 are included in an atmosphere oxygen concentration changing unit that changes the oxygen concentration in the atmosphere in contact with the substrate W.

[0041] The processing cup 23 includes a plurality of guards 25 that receive liquid discharged outward from the substrate W, a plurality of cups 26 that receive liquid guided downward by the plurality of guards 25, and a cylindrical outer wall member 24 that surrounds the plurality of guards 25 and the plurality of cups 26. Figure 2 shows an example in which two guards 25 and two cups 26 are provided. The guard 25 includes a cylindrical guard tubular portion 25b that surrounds the spin chuck 10 and an annular guard ceiling portion 25a that extends obliquely upward from the upper end of the guard tubular portion 25b toward the rotation axis A1. The multiple guard ceiling portions 25a are stacked one on top of the other, and the multiple guard tubular portions 25b are arranged concentrically. The multiple cups 26 are respectively arranged below the multiple guard tubular portions 25b. The cups 26 form annular liquid-receiving grooves that open upward.

[0042] The processing unit 2 includes a guard lifting unit 27 that raises and lowers the multiple guards 25 individually. The guard lifting unit 27 positions the guards 25 at any position between the upper position and the lower position. The upper position is a position where the upper end 25u of the guard 25 is located above the holding position where the substrate W held by the spin chuck 10 is located. The lower position is a position where the upper end 25u of the guard 25 is located below the holding position. The annular upper end of the guard ceiling portion 25a corresponds to the upper end 25u of the guard 25. The upper end 25u of the guard 25 surrounds the substrate W and the spin base 12 in a plan view.

[0043] When a processing liquid is supplied to the substrate W while the spin chuck 10 is rotating the substrate W, the processing liquid supplied to the substrate W is shaken off from the substrate W. When the processing liquid is supplied to the substrate W, the upper end 25u of at least one guard 25 is positioned above the substrate W. Therefore, the processing liquid, such as a chemical liquid or a rinse liquid, discharged from the substrate W is received by one of the guards 25 and guided to the cup 26 corresponding to this guard 25.

[0044] 3, the processing unit 2 includes a lifting frame 32 disposed above the spin chuck 10, a blocking member 33 suspended from the lifting frame 32, a center nozzle 45 inserted into the blocking member 33, and a blocking member lifting unit 31 that raises and lowers the lifting frame 32, thereby raising and lowering the blocking member 33 and the center nozzle 45. The lifting frame 32, the blocking member 33, and the center nozzle 45 are disposed below the straightening plate 8.

[0045] The blocking member 33 includes a disk portion 36 disposed above the spin chuck 10 and a cylindrical portion 37 extending downward from the outer periphery of the disk portion 36. The blocking member 33 includes an inner surface that is cup-shaped and concave upward. The inner surface of the blocking member 33 includes a lower surface 36L of the disk portion 36 and an inner circumferential surface 37i of the cylindrical portion 37. Hereinafter, the lower surface 36L of the disk portion 36 may be referred to as the lower surface 36L of the blocking member 33.

[0046] The lower surface 36L of the disc portion 36 is a facing surface that faces the upper surface of the substrate W. The lower surface 36L of the disc portion 36 is parallel to the upper surface of the substrate W. The inner circumferential surface 37i of the cylindrical portion 37 extends downward from the outer periphery of the lower surface 36L of the disc portion 36. The inner diameter of the cylindrical portion 37 increases toward the lower end of the inner circumferential surface 37i of the cylindrical portion 37. The inner diameter of the lower end of the inner circumferential surface 37i of the cylindrical portion 37 is larger than the diameter of the substrate W. The inner diameter of the lower end of the inner circumferential surface 37i of the cylindrical portion 37 may be larger than the outer diameter of the spin base 12. When the blocking member 33 is placed in a lower position (position shown in FIG. 2 ), which will be described later, the substrate W is surrounded by the inner circumferential surface 37i of the cylindrical portion 37.

[0047] The lower surface 36L of the disc portion 36 is annular and surrounds the rotation axis A1. The inner peripheral edge of the lower surface 36L of the disc portion 36 forms an upper central opening 38 that opens at the center of the lower surface 36L of the disc portion 36. The inner peripheral surface of the blocking member 33 forms a through hole that extends upward from the upper central opening 38. The through hole of the blocking member 33 passes through the blocking member 33 in the vertical direction. The center nozzle 45 is inserted into the through hole of the blocking member 33. The outer diameter of the lower end of the center nozzle 45 is smaller than the diameter of the upper central opening 38.

[0048] The inner peripheral surface of the blocking member 33 is coaxial with the outer peripheral surface of the center nozzle 45. The inner peripheral surface of the blocking member 33 surrounds the outer peripheral surface of the center nozzle 45 at a distance in the radial direction (direction perpendicular to the rotation axis A1). The inner peripheral surface of the blocking member 33 and the outer peripheral surface of the center nozzle 45 form an upper cylindrical passage 39 extending vertically. The center nozzle 45 protrudes upward from the lifting frame 32 and the blocking member 33. When the blocking member 33 is suspended from the lifting frame 32, the lower end of the center nozzle 45 is positioned above the lower surface 36L of the disc portion 36. Processing liquids such as chemical solutions and rinse liquids are discharged downward from the lower end of the center nozzle 45.

[0049] The blocking member 33 includes a cylindrical connecting portion 35 extending upward from a disc portion 36, and an annular flange portion 34 extending outward from the upper end of the connecting portion 35. The flange portion 34 is disposed higher than the disc portion 36 and the cylindrical portion 37 of the blocking member 33. The flange portion 34 is parallel to the disc portion 36. The outer diameter of the flange portion 34 is smaller than the outer diameter of the cylindrical portion 37. The flange portion 34 is supported by a lower plate 32L of the lifting frame 32, which will be described later.

[0050] The lifting frame 32 includes an upper plate 32u located above the flange portion 34 of the blocking member 33, a side ring 32s extending downward from the upper plate 32u and surrounding the flange portion 34, and an annular lower plate 32L extending inward from the lower end of the side ring 32s and located below the flange portion 34 of the blocking member 33. The outer periphery of the flange portion 34 is disposed between the upper plate 32u and the lower plate 32L. The outer periphery of the flange portion 34 is movable up and down between the upper plate 32u and the lower plate 32L.

[0051] The lifting frame 32 and the blocking member 33 include positioning protrusions 41 and positioning holes 42 that restrict relative movement of the lifting frame 32 and the blocking member 33 in the circumferential direction (the direction around the rotation axis A1) when the blocking member 33 is supported by the lifting frame 32. Fig. 2 shows an example in which multiple positioning protrusions 41 are provided on the lower plate 32L and multiple positioning holes 42 are provided on the flange portion 34. The positioning protrusions 41 may also be provided on the flange portion 34 and the positioning holes 42 may also be provided on the lower plate 32L.

[0052] The positioning protrusions 41 are arranged on a circle whose center is located on the rotation axis A1. Similarly, the positioning holes 42 are arranged on a circle whose center is located on the rotation axis A1. The positioning holes 42 are arranged in the circumferential direction with the same regularity as the positioning protrusions 41. The positioning protrusions 41 protruding upward from the upper surface of the lower plate 32L are inserted into the positioning holes 42 extending upward from the lower surface of the flange portion 34. This restricts movement of the blocking member 33 in the circumferential direction relative to the lifting frame 32.

[0053] The blocking member 33 includes a plurality of upper support portions 43 that protrude downward from the inner surface of the blocking member 33. The spin chuck 10 includes a plurality of lower support portions 44 that respectively support the plurality of upper support portions 43. The plurality of upper support portions 43 are surrounded by the cylindrical portion 37 of the blocking member 33. The lower ends of the upper support portions 43 are located higher than the lower ends of the cylindrical portion 37. The radial distance from the rotation axis A1 to the upper support portions 43 is greater than the radius of the substrate W. Similarly, the radial distance from the rotation axis A1 to the lower support portions 44 is greater than the radius of the substrate W. The lower support portions 44 protrude upward from the upper surface 12u of the spin base 12. The lower support portions 44 are located outward of the chuck pins 11.

[0054] The upper support parts 43 are arranged on a circle whose center is located on the rotation axis A1. Similarly, the lower support parts 44 are arranged on a circle whose center is located on the rotation axis A1. The lower support parts 44 are arranged in the circumferential direction with the same regularity as the upper support parts 43. The lower support parts 44 rotate around the rotation axis A1 together with the spin base 12. The rotation angle of the spin base 12 is changed by the spin motor 14. When the spin base 12 is positioned at the reference rotation angle, the upper support parts 43 respectively overlap the lower support parts 44 in a plan view.

[0055] The blocking member lifting unit 31 is connected to the lifting frame 32. When the blocking member lifting unit 31 lowers the lifting frame 32 in a state where the flange portion 34 of the blocking member 33 is supported by the lower plate 32L of the lifting frame 32, the blocking member 33 also lowers. When the spin base 12 is positioned at a reference rotation angle where the multiple upper support portions 43 respectively overlap the multiple lower support portions 44 in a plan view, when the blocking member lifting unit 31 lowers the blocking member 33, the lower end portions of the upper support portions 43 come into contact with the upper end portions of the lower support portions 44. As a result, the multiple upper support portions 43 are supported by the multiple lower support portions 44, respectively.

[0056] When the shielding member lifting unit 31 lowers the lifting frame 32 after the upper support portion 43 of the shielding member 33 comes into contact with the lower support portion 44 of the spin chuck 10, the lower plate 32L of the lifting frame 32 moves downward relative to the flange portion 34 of the shielding member 33. As a result, the lower plate 32L moves away from the flange portion 34, and the positioning protrusions 41 come out of the positioning holes 42. Furthermore, since the lifting frame 32 and the center nozzle 45 move downward relative to the shielding member 33, the height difference between the lower end of the center nozzle 45 and the lower surface 36L of the disk portion 36 of the shielding member 33 decreases. At this time, the lifting frame 32 is positioned at a height (a lower position, described later) at which the flange portion 34 of the shielding member 33 does not come into contact with the upper plate 32u of the lifting frame 32.

[0057] The blocking member lifting unit 31 positions the lifting frame 32 at any position between the upper position (the position shown in FIG. 3) and the lower position (the position shown in FIG. 2). The upper position is a position where the positioning protrusions 41 are inserted into the positioning holes 42 and the flange portions 34 of the blocking member 33 are in contact with the lower plate 32L of the lifting frame 32. In other words, the upper position is a position where the blocking member 33 is suspended from the lifting frame 32. The lower position is a position where the lower plate 32L is separated from the flange portions 34 and the positioning protrusions 41 are removed from the positioning holes 42. In other words, the lower position is a position where the connection between the lifting frame 32 and the blocking member 33 is released and the blocking member 33 is not in contact with any part of the lifting frame 32.

[0058] When the lifting frame 32 and the shielding member 33 are moved to the lower position, the lower end of the cylindrical portion 37 of the shielding member 33 is positioned lower than the lower surface of the substrate W, and the space between the upper surface of the substrate W and the lower surface 36L of the shielding member 33 is surrounded by the cylindrical portion 37 of the shielding member 33. Therefore, the space between the upper surface of the substrate W and the lower surface 36L of the shielding member 33 is sealed not only from the atmosphere above the shielding member 33, but also from the atmosphere around the shielding member 33. This increases the degree of sealing of the space between the upper surface of the substrate W and the lower surface 36L of the shielding member 33.

[0059] Furthermore, when the lift frame 32 and the blocking member 33 are positioned in the lower position, the blocking member 33 will not collide with the lift frame 32 even if it is rotated about the rotation axis A1 relative to the lift frame 32. When the upper support portion 43 of the blocking member 33 is supported by the lower support portion 44 of the spin chuck 10, the upper support portion 43 and the lower support portion 44 mesh with each other, restricting relative movement of the upper support portion 43 and the lower support portion 44 in the circumferential direction. When the spin motor 14 rotates in this state, the torque of the spin motor 14 is transmitted to the blocking member 33 via the upper support portion 43 and the lower support portion 44. As a result, the blocking member 33 rotates in the same direction and at the same speed as the spin base 12, with the lift frame 32 and the central nozzle 45 stationary.

[0060] The central nozzle 45 includes a plurality of liquid outlets for discharging a liquid and a gas outlet for discharging a gas. The plurality of liquid outlets include a chemical liquid outlet 46 for discharging a chemical liquid, an etching liquid outlet 47 for discharging an etching liquid, and an upper rinse liquid outlet 48 for discharging a rinse liquid. The gas outlet is an upper gas outlet 49 for discharging an inert gas. The chemical liquid outlet 46, the etching liquid outlet 47, and the upper rinse liquid outlet 48 open at the lower end of the central nozzle 45. The upper gas outlet 49 opens at the outer circumferential surface of the central nozzle 45.

[0061] The chemical liquid is, for example, a liquid containing at least one of sulfuric acid, nitric acid, hydrochloric acid, hydrofluoric acid, phosphoric acid, acetic acid, ammonia water, hydrogen peroxide, organic acid (e.g., citric acid, oxalic acid, etc.), organic alkali (e.g., TMAH (tetramethylammonium hydroxide), etc.), surfactant, polyhydric alcohol, and corrosion inhibitor. Sulfuric acid, nitric acid, hydrochloric acid, hydrofluoric acid, phosphoric acid, acetic acid, ammonia water, hydrogen peroxide, citric acid, oxalic acid, and TMAH are also etching liquids.

[0062] 2 and the like show an example in which the chemical liquid is DHF (dilute hydrofluoric acid). Also, FIG. 2 and the like show an example in which the rinse liquid supplied to the center nozzle 45 is pure water, and the inert gas supplied to the center nozzle 45 is nitrogen gas. The rinse liquid supplied to the center nozzle 45 may be a rinse liquid other than pure water. The inert gas supplied to the center nozzle 45 may be an inert gas other than nitrogen gas.

[0063] The substrate processing apparatus 1 includes a chemical liquid pipe 50 that guides a chemical liquid to the center nozzle 45, a chemical liquid valve 51 installed in the chemical liquid pipe 50, an etching liquid pipe 52 that guides an etching liquid to the center nozzle 45, an etching liquid valve 53 installed in the etching liquid pipe 52, an upper rinse liquid pipe 54 that guides a rinse liquid to the center nozzle 45, and an upper rinse liquid valve 55 installed in the upper rinse liquid pipe 54. The substrate processing apparatus 1 further includes an upper gas pipe 56 that guides a gas to the center nozzle 45, an upper gas valve 57 installed in the upper gas pipe 56, and an upper gas flow rate adjustment valve 58 that changes the flow rate of gas supplied from the upper gas pipe 56 to the center nozzle 45.

[0064] When the chemical liquid valve 51 is opened, the chemical liquid is supplied to the center nozzle 45 and is discharged downward from the chemical liquid discharge port 46 opening at the lower end of the center nozzle 45. When the etching liquid valve 53 is opened, the etching liquid is supplied to the center nozzle 45 and is discharged downward from the etching liquid discharge port 47 opening at the lower end of the center nozzle 45. When the upper rinse liquid valve 55 is opened, the rinse liquid is supplied to the center nozzle 45 and is discharged downward from the upper rinse liquid discharge port 48 opening at the lower end of the center nozzle 45. In this way, a processing liquid such as the chemical liquid is supplied to the upper surface of the substrate W.

[0065] When the upper gas valve 57 is opened, nitrogen gas guided by the upper gas pipe 56 is supplied to the center nozzle 45 at a flow rate corresponding to the aperture of the upper gas flow rate adjustment valve 58. The nitrogen gas is then discharged obliquely downward from the upper gas outlet port 49, which opens on the outer peripheral surface of the center nozzle 45. The nitrogen gas then flows circumferentially through the upper cylindrical passage 39 and then downward. Upon reaching the lower end of the upper cylindrical passage 39, the nitrogen gas flows downward from the lower end of the upper cylindrical passage 39. The nitrogen gas then flows radially in all directions through the space between the upper surface of the substrate W and the lower surface 36L of the blocking member 33. This fills the space between the substrate W and the blocking member 33 with nitrogen gas, reducing the oxygen concentration in the atmosphere. The oxygen concentration in the space between the substrate W and the blocking member 33 is changed according to the apertures of the upper gas valve 57 and the upper gas flow rate adjustment valve 58. The upper gas valve 57 and the upper gas flow rate adjustment valve 58 are included in an atmosphere oxygen concentration changing unit.

[0066] Figure 4 is a graph showing an example of the relationship between the etching rate of three crystal planes of silicon and the concentration of propylene glycol in the etching solution. Figures 5A and 5B are diagrams illustrating the mechanism assumed when a compound inhibits contact between hydroxide ions and polysilicon. "PG" in Figures 4, 5A, and 5B represents propylene glycol.

[0067] The substrate processing apparatus 1 supplies to the substrate W an etching solution that corrodes and dissolves a portion of the substrate W, and a compound that reduces the anisotropy of the etching solution with respect to silicon single crystal, either separately or mixed in advance. The etching solution is an alkaline liquid that etches an etching target 96 (see FIG. 5A) representing at least one of single crystal silicon, polysilicon, and amorphous silicon, while not etching or barely etching non-etching targets such as silicon oxide and silicon nitride. The pH (hydrogen ion exponent) of the etching solution is, for example, 12 or higher. Under the same processing conditions, the etching amount of the etching target 96 per unit time is greater than the etching amount of the non-etching target per unit time.

[0068] An etching solution is a liquid that performs anisotropic etching on single crystal silicon (including single crystal silicon in polysilicon). In other words, if the processing conditions are the same, when etching the (110), (100), and (111) silicon surfaces with an etching solution, the etching rate for the (110) surface is the highest and the etching rate for the (111) surface is the lowest. Therefore, the etching rate differs for each silicon crystal surface.

[0069] The etching solution may be an aqueous solution containing an alkali metal hydroxide such as sodium or potassium (NaOH or KOH), or a quaternary ammonium hydroxide such as TMAH. The quaternary ammonium hydroxide may be at least one of TMAH, TBAH (tetrabutylammonium hydroxide), TPeAH (tetrapentylammonium hydroxide), THAH (tetrahexylammonium hydroxide), TEAH (tetraethylammonium hydroxide), TPAH (tetrapropylammonium hydroxide), and choline hydroxide, or may be other than these. All of these are included in the organic alkali. Note that in this paragraph, TMAH refers to the anhydrous form, not the aqueous solution. This also applies to other quaternary ammonium hydroxides such as TBAH.

[0070] When quaternary ammonium hydroxide dissolves in water, it dissociates into positive ions (cations) and hydroxide ions. Therefore, hydroxide ions are present in an aqueous solution of quaternary ammonium hydroxide. Similarly, hydroxide ions are also present in an aqueous solution of hydroxides of alkali metals such as sodium and potassium. The compound supplied to the substrate W is an inhibitor that inhibits contact between the hydroxide ions and the etching target 96. The inhibitor molecule is preferably larger than the hydroxide ion. Furthermore, the inhibitor is preferably a water-soluble substance that dissolves in water. The inhibitor may be a surfactant having both hydrophilic and hydrophobic groups. The inhibitor may also be an insoluble substance that does not dissolve in water, as long as it is uniformly dispersed in the etching solution.

[0071] The etching solution is supplied to the substrate W either mixed with or without a compound. The compound is a substance that dissolves in the etching solution. The compound may be a glycol or an ether, or a substance other than glycols and ethers, such as glycerin. The compound may be a mixture of two or more substances of different types, or a mixture of two or more substances belonging to the same type. In the latter case, the compound may be two or more substances belonging to any of glycols, ethers, and glycerin.

[0072] The glycol may be any one of ethylene glycol, diethylene glycol, and propylene glycol. The glycol is preferably propylene glycol. The glycol is a hydroxyl group containing silicon (Si) and hydroxide ions (OH - ) is an example of a substance that does not react with the atoms involved in the reaction between silicon and hydroxide ions. Glycol is also an example of a substance that does not act as a catalyst for this reaction.

[0073] When an alkaline etching solution containing a compound (a mixed solution of a compound, a hydroxide, and water) is supplied to the substrate W, the concentration of the hydroxide such as TMAH is, for example, 0.1 to 25 wt %, and the concentration of the compound is, for example, 0.001 to 40 wt %. The concentration of the hydroxide is preferably 0.25 to 20 wt %. The concentration of the compound is preferably 0.5 to 30%.

[0074] 5A and 5B show an example in which an etching solution containing propylene glycol, which is an example of a compound (a mixed solution of the etching solution and propylene glycol), is supplied to polysilicon, which is an example of an etching target 96. In FIGS. 5A and 5B, the "cation" and "OH - " is a separated hydroxide (alkali metal hydroxide or quaternary ammonium hydroxide) contained in the etching solution.

[0075] Silicon contained in the etching target 96 such as polysilicon is represented by the formula "Si+4OH - →Si(OH)4+4e - As shown in the figure, the compound reacts with hydroxide ions. This causes the silicon contained in the etching object 96 to dissolve in the etching solution, and etching of the etching object 96 progresses. The compounds contained in the etching solution act as a steric barrier to the hydroxide ions. In other words, compounds suspended in the etching solution, or compounds adsorbed or coordinated to the polysilicon, block the movement of hydroxide ions in the etching solution toward the polysilicon. This reduces the number of hydroxide ions that reach the polysilicon, and slows the etching rate of the polysilicon. It is believed that this mechanism is what prevents the compounds from contacting the hydroxide ions with the polysilicon.

[0076] Although the decrease in etching rate occurs on multiple crystal planes of silicon contained in polysilicon, the etching rate decreases relatively more on the crystal planes with the highest etching rate among the multiple crystal planes of silicon. This reduces the difference in etching rate among the multiple crystal planes, and the anisotropy of the etching solution with respect to the silicon single crystal is reduced. In other words, polysilicon is etched uniformly regardless of the plane orientation of the silicon exposed on the surface of the polysilicon. It is believed that this mechanism allows polysilicon to be etched by a uniform amount everywhere.

[0077] Figure 4 shows the measured etching rates for the (110), (100), and (111) planes when etching single-crystal silicon using three types of TMAH with different propylene glycol concentrations (zero, first, and second concentrations). The etching conditions used to obtain the measurements shown in Figure 4 were the same except for the concentration of propylene glycol in the TMAH. For example, the temperature of the TMAH was 40°C, and the concentration of TMAH without added propylene glycol was 5 wt% (mass percent). The dissolved oxygen concentration of the TMAH was previously reduced.

[0078] As shown in Figure 4, when the propylene glycol concentration is zero, the etching rate for the (110) plane is the highest and the etching rate for the (111) plane is the lowest. As can be seen from the three curves in Figure 4, adding propylene glycol to TMAH decreases the etching rate. Furthermore, for each crystal plane, the etching rate decreases as the propylene glycol concentration increases.

[0079] However, in the range of propylene glycol concentration from zero to the first concentration, the etching rates of the (110) and (100) planes decrease rapidly, while the etching rate of the (111) plane decreases very slowly. Therefore, in this range, the difference between the maximum and minimum etching rates decreases as the propylene glycol concentration increases.

[0080] When the concentration of propylene glycol exceeds the first concentration, the rate of decrease in the etching rate (the ratio of the absolute value of the change in the etching rate to the absolute value of the change in the propylene glycol concentration) decreases, but up to a value approximately halfway between the first and second concentrations, the rate of decrease in the etching rate for the (110) and (100) planes is greater than the rate of decrease in the etching rate for the (111) plane. Therefore, even within the range of the propylene glycol concentration approximately halfway between the first and second concentrations, the difference between the maximum and minimum etching rates decreases as the propylene glycol concentration increases.

[0081] Thus, adding propylene glycol to TMAH, which exhibits anisotropy with respect to single-crystal silicon, reduces the plane orientation selectivity, i.e., the difference between the maximum and minimum etching rates, and reduces the anisotropy of TMAH with respect to single-crystal silicon. On the other hand, within the range of propylene glycol concentrations up to values ​​near the middle between the first and second concentrations, the etching rates of the (110) and (100) planes decrease at a large rate as the propylene glycol concentration increases. Therefore, the concentration of propylene glycol can be set according to the required etching uniformity and the required etching rate.

[0082] For example, an inhibitor such as propylene glycol may be added in excess to the etching solution. According to the measurement results shown in Figure 4, adding a small amount of propylene glycol (e.g., about 5 to 10 wt%) has a relatively small effect on reducing anisotropy, but adding a large amount of propylene glycol (e.g., 20 wt% or more), i.e., adding an excessive amount of propylene glycol, significantly reduces anisotropy. On the other hand, the etching rate decreases, so the concentration of propylene glycol should be selected depending on the required quality and the allowable processing time.

[0083] The tendency shown in FIG. 4 was also confirmed in combinations other than TMAH and propylene glycol. Therefore, the etching solution is not limited to TMAH, and the compound is not limited to propylene glycol. Furthermore, it is expected that the tendency shown in FIG. 4 will be observed not only when an etching solution containing a compound is supplied to the etching target 96, but also when the compound and the etching solution are supplied separately to the substrate W and mixed on the etching target 96. Therefore, the compound and the etching solution may be supplied separately to the substrate W.

[0084] If the conditions other than the type of compound (including the combination of substances when the compound is a mixture of two or more substances) are the same, different types of compound supplied to the etching target 96 will result in different etching rates for at least one of the silicon (110), (100), and (111) faces. Therefore, the type of compound can be selected depending on the required quality and the allowable processing time.

[0085] When an etching solution is supplied to the etching object 96 without supplying a compound to the etching object 96, as the temperature of the etching solution increases, the etching rates of the (110) and (100) planes increase by a larger amount than the etching rate of the (111) plane. Also, in this case, as the temperature of the etching solution decreases, the etching rates of the (110) and (100) planes decrease by a larger amount than the etching rate of the (111) plane.

[0086] Therefore, when an etching liquid is supplied to the etching object 96 without supplying a compound to the etching object 96, the difference between the minimum and maximum etching rates of silicon increases as the temperature of the etching liquid increases. Conversely, when an etching liquid is supplied to the etching object 96 without supplying a compound to the etching object 96, the difference between the minimum and maximum etching rates of silicon decreases as the temperature of the etching liquid decreases. These phenomena also occur when an etching liquid and a compound are supplied to the etching object 96. Therefore, the temperatures of the etching liquid and the compound can be set according to the required quality and the allowable processing time.

[0087] 6 is a schematic diagram showing a processing liquid supply unit 61 of the substrate processing apparatus 1 that supplies a processing liquid such as an etching liquid to a substrate W. FIG. 6 shows an example in which the etching liquid is mixed with a compound before being supplied to the substrate W. The substrate processing apparatus 1 includes a processing liquid supply unit 61 that supplies a processing liquid such as an etching liquid to the substrate W. The processing liquid supply unit 61 includes the above-mentioned center nozzle 45, etching liquid pipe 52, etching liquid valve 53, etc. The processing liquid supply unit 61 is an example of the first etching means and the second etching means.

[0088] In addition to the central nozzle 45 and the like, the processing liquid supply unit 61 includes a stock solution tank 62 for storing an alkaline etching liquid concentrate (undiluted alkaline etching liquid), a first dilution liquid tank 70 for storing a first dilution liquid for diluting the etching liquid concentrate, and a second dilution liquid tank 75 for storing a second dilution liquid for diluting the etching liquid concentrate. The first and second dilutions are liquids with the same components but different dissolved oxygen concentrations. Figure 6 shows an example in which the first and second dilutions are pure water (DIW) with the aforementioned compounds dissolved therein. The dissolved oxygen concentration of the first dilution is lower than that of the second dilution. The first and second dilutions may be alkaline etching solutions, as long as their hydroxide concentrations are lower than those of the original etching solution.

[0089] The concentrate in the concentrate tank 62 is supplied to the center nozzle 45 via the mixing valve 80. Similarly, the first diluent in the first diluent tank 70 is supplied to the center nozzle 45 via the mixing valve 80, and the second diluent in the second diluent tank 75 is supplied to the center nozzle 45 via the mixing valve 80. The concentrate of the etching solution is mixed with at least one of the first diluent and the second diluent in the mixing valve 80. As a result, a diluted concentrate, i.e., an etching solution, is generated and supplied to the center nozzle 45.

[0090] The processing liquid supply unit 61 may further include an in-line mixer 81 that mixes the etching liquid that has passed through the mixing valve 80 before being discharged from the central nozzle 45. Fig. 6 shows an example in which the in-line mixer 81 is disposed upstream of the etching liquid valve 53. The in-line mixer 81 is a static mixer that includes a pipe 81p inserted in the raw liquid piping 67 and a stirring fin 81f that is disposed within the pipe 81p and twisted around an axis extending in the direction of liquid flow.

[0091] The processing liquid supply unit 61 includes a circulation pipe 63 for circulating the raw liquid in the raw liquid tank 62, a circulation pump 64 for sending the raw liquid in the raw liquid tank 62 to the circulation pipe 63, a filter 66 for removing foreign matter such as particles from the raw liquid returning to the raw liquid tank 62, and a temperature regulator 65 for changing the temperature of the raw liquid in the raw liquid tank 62 by heating or cooling the raw liquid. The circulation pump 64 constantly sends the concentrate in the concentrate tank 62 into the circulation pipe 63. The concentrate in the concentrate tank 62 flows into the circulation pipe 63 through the upstream end of the circulation pipe 63 and returns to the concentrate tank 62 through the downstream end of the circulation pipe 63. In this way, the concentrate circulates through the circulation path formed by the concentrate tank 62 and the circulation pipe 63.

[0092] The temperature regulator 65 maintains the temperature of the concentrate in the concentrate tank 62 at a constant temperature that is higher or lower than room temperature (for example, 20 to 30°C). The temperature regulator 65 may be installed in the circulation pipe 63, or may be disposed inside the concentrate tank 62. FIG. 6 shows an example of the former. The temperature regulator 65 may be a heater that heats the liquid to a temperature higher than room temperature, or a cooler that cools the liquid to a temperature lower than room temperature, or may have both heating and cooling functions.

[0093] The processing liquid supply unit 61 further includes a raw liquid pipe 67 that guides the raw liquid from the circulation pipe 63 toward the central nozzle 45, a flow rate control valve 69 that changes the flow rate of the raw liquid flowing downstream in the raw liquid pipe 67, and an in-line heater 68 that heats the raw liquid that has flowed into the raw liquid pipe 67. The raw liquid in the circulation pipe 63 flows into the raw liquid pipe 67 through the upstream end of the raw liquid pipe 67 and is supplied to the mixing valve 80 through the downstream end of the raw liquid pipe 67. At this time, the raw liquid is supplied to the mixing valve 80 at a flow rate corresponding to the opening of the flow rate adjustment valve 69. When raw liquid at a temperature higher than the temperature of the raw liquid in the raw liquid tank 62 is supplied to the mixing valve 80, the raw liquid is heated by the in-line heater 68 before being supplied to the mixing valve 80.

[0094] The processing liquid supply unit 61 includes a first diluent pipe 71 that guides the first diluent from the first diluent tank 70 toward the central nozzle 45, a first diluent pump 72 that sends the first diluent in the first diluent tank 70 to the first diluent pipe 71, a filter 73 that removes foreign matter such as particles from the first diluent flowing toward the central nozzle 45, and a flow control valve 74 that changes the flow rate of the first diluent flowing downstream in the first diluent pipe 71.

[0095] The processing liquid supply unit 61 further includes a second diluent pipe 76 that guides the second diluent from the second diluent tank 75 toward the central nozzle 45, a second diluent pump 77 that sends the second diluent in the second diluent tank 75 to the second diluent pipe 76, a filter 78 that removes foreign matter such as particles from the second diluent flowing toward the central nozzle 45, and a flow control valve 79 that changes the flow rate of the second diluent flowing downstream in the second diluent pipe 76.

[0096] When circulating the first diluent in the first diluent tank 70, a configuration similar to that for the stock solution may be adopted. That is, a circulation pipe 63 and a circulation pump 64 for the first diluent may be provided. When supplying the first diluent, which is higher or lower than room temperature, to the mixing valve 80, at least one of a temperature regulator 65 for the first diluent and an in-line heater 68 may be provided. The same applies to the second diluent.

[0097] The mixing valve 80 includes a plurality of valves that can be opened and closed individually and a plurality of flow paths connected to the plurality of valves. Fig. 6 shows an example in which the mixing valve 80 includes three valves (a first valve V1, a second valve V2, and a third valve V3), three inlet ports (a first inlet port Pi1, a second inlet port Pi2, and a third inlet port Pi3), and one outlet port Po. The concentrate pipe 67 is connected to the first inlet port Pi1. The first diluent pipe 71 is connected to the second inlet port Pi2, and the second diluent pipe 76 is connected to the third inlet port Pi3. The etching solution pipe 52 is connected to the outlet port Po.

[0098] When the first valve V1 is opened, the concentrate in the concentrate pipe 67 flows into the mixing valve 80 through the first inlet port Pi1 and is discharged from the outlet port Po to the etching liquid pipe 52. Similarly, when the second valve V2 is opened, the first diluent in the first diluent pipe 71 flows into the mixing valve 80 through the second inlet port Pi2 and is discharged from the outlet port Po to the etching liquid pipe 52. When the third valve V3 is opened, the second diluent in the second diluent pipe 76 flows into the mixing valve 80 through the third inlet port Pi3 and is discharged from the outlet port Po to the etching liquid pipe 52.

[0099] When the first valve V1 and the second valve V2 are opened, the undiluted solution is supplied to the mixing valve 80 at a flow rate corresponding to the opening of the flow rate adjustment valve 69, and the first diluent is supplied to the mixing valve 80 at a flow rate corresponding to the opening of the flow rate adjustment valve 74. As a result, the undiluted etching solution diluted with the first diluent is supplied from the mixing valve 80 to the etching solution pipe 52 and is ejected from the central nozzle 45 toward the substrate W.

[0100] When the first valve V1 and the third valve V3 are opened, the undiluted solution is supplied to the mixing valve 80 at a flow rate corresponding to the opening of the flow rate adjustment valve 69, and the second diluent is supplied to the mixing valve 80 at a flow rate corresponding to the opening of the flow rate adjustment valve 79. As a result, the undiluted etching solution diluted with the second diluent is supplied from the mixing valve 80 to the etching solution pipe 52 and is ejected from the central nozzle 45 toward the substrate W.

[0101] When the first valve V1, the second valve V2, and the third valve V3 are opened, the stock solution, the first diluent, and the second diluent are supplied to the mixing valve 80, and the stock solution of the etching solution diluted with the first diluent and the second diluent is supplied from the mixing valve 80 to the etching solution pipe 52. The ratio of the first diluent and the second diluent contained in the etching solution is adjusted by the opening of the flow rate adjustment valve 74 and the flow rate adjustment valve 79.

[0102] Regardless of the diluent used to dilute the stock solution, the ratio of the diluent (at least one of the first diluent and the second diluent) to the stock solution is constant. For example, if the ratio of the diluent (volume of diluent / volume of stock solution) when the stock solution is diluted only with the first diluent is ratio X, the ratio of the diluent when the stock solution is diluted only with the second diluent is also ratio X. The ratio of the diluent when the stock solution is diluted with both the first diluent and the second diluent is also ratio X. Therefore, if the amount of stock solution supplied to the mixing valve 80 is constant, the stock solution is diluted with a fixed amount of diluent. The ratio of the stock solution contained in the etching solution may be smaller, larger, or equal to the ratio of the diluent contained in the etching solution.

[0103] The substrate processing apparatus 1 is equipped with a dissolved oxygen concentration changing unit that adjusts the dissolved oxygen concentration of the etching solution. Fig. 6 shows an example in which the dissolved oxygen concentration changing unit includes an undiluted solution adjusting unit 82A that adjusts the dissolved oxygen concentration of the undiluted solution, a first diluent adjusting unit 82B that adjusts the dissolved oxygen concentration of the first diluent, and a second diluent adjusting unit 82C that adjusts the dissolved oxygen concentration of the second diluent.

[0104] The concentrate adjustment unit 82A includes a gas pipe 83 that supplies gas into the concentrate tank 62 to dissolve the gas in the concentrate in the concentrate tank 62. The concentrate adjustment unit 82A further includes an inert gas pipe 84 that supplies inert gas to the gas pipe 83, an inert gas valve 85 that opens and closes between an open state in which the inert gas flows from the inert gas pipe 84 to the gas pipe 83 and a closed state in which the inert gas is blocked by the inert gas pipe 84, and a flow rate adjustment valve 86 that changes the flow rate of the inert gas supplied from the inert gas pipe 84 to the gas pipe 83.

[0105] The gas pipe 83 is a bubbling pipe including a gas outlet 83p disposed in the concentrate in the concentrate tank 62. When the inert gas valve 85 is switched from a closed state to an open state, an inert gas such as nitrogen gas is discharged from the gas outlet 83p at a flow rate corresponding to the opening of the flow rate control valve 86. This causes a large number of bubbles to form in the concentrate in the concentrate tank 62, and the inert gas dissolves in the concentrate in the concentrate tank 62. At this time, dissolved oxygen is discharged from the concentrate, and the dissolved oxygen concentration of the concentrate decreases. The dissolved oxygen concentration of the concentrate in the concentrate tank 62 can be changed by changing the flow rate of the nitrogen gas discharged from the gas outlet 83p.

[0106] The first diluent adjustment unit 82B includes a gas pipe 87 that supplies gas into the first diluent tank 70 to dissolve the gas in the first diluent in the first diluent tank 70. The first diluent adjustment unit 82B further includes an inert gas pipe 88 that supplies inert gas to the gas pipe 87, an inert gas valve 89 that opens and closes between an open state in which inert gas flows from the inert gas pipe 88 to the gas pipe 87 and a closed state in which the inert gas is blocked by the inert gas pipe 88, and a flow rate adjustment valve 90 that changes the flow rate of the inert gas supplied from the inert gas pipe 88 to the gas pipe 87.

[0107] The gas pipe 87 is a bubbling pipe including a gas outlet 87p disposed in the first diluent in the first diluent tank 70. When the inert gas valve 89 is switched from a closed state to an open state, an inert gas such as nitrogen gas is discharged from the gas outlet 87p at a flow rate corresponding to the aperture of the flow rate control valve 90. This causes a large number of bubbles to form in the first diluent in the first diluent tank 70, and the inert gas dissolves in the first diluent in the first diluent tank 70. At this time, dissolved oxygen is discharged from the first diluent, and the dissolved oxygen concentration of the first diluent in the first diluent tank 70 decreases. The dissolved oxygen concentration of the first diluent in the first diluent tank 70 can be changed by changing the flow rate of the nitrogen gas discharged from the gas outlet 87p.

[0108] The second diluent adjustment unit 82C includes a gas pipe 91 that supplies gas into the second diluent tank 75 to dissolve the gas in the second diluent in the second diluent tank 75. The second diluent adjustment unit 82C also includes an oxygen pipe 92 that supplies oxygen-containing gas to the gas pipe 91, an oxygen valve 93 that opens and closes between an open state in which the oxygen-containing gas flows from the oxygen pipe 92 to the gas pipe 91 and a closed state in which the oxygen-containing gas is blocked by the oxygen pipe 92, and a flow rate adjustment valve 94 that changes the flow rate of the oxygen-containing gas supplied from the oxygen pipe 92 to the gas pipe 91. The oxygen-containing gas is an example of a dissolved gas. The oxygen-containing gas may be oxygen gas or a mixture of oxygen gas and a gas other than oxygen gas. Figure 6 shows an example of the oxygen-containing gas being dry air (dry, clean air) containing nitrogen and oxygen in a ratio of approximately 8:2.

[0109] The gas pipe 91 is a bubbling pipe including a gas outlet 91p disposed in the second diluent in the second diluent tank 75. When the oxygen valve 93 is switched from a closed state to an open state, oxygen-containing gas is discharged from the gas outlet 91p at a flow rate corresponding to the aperture of the flow control valve 94. This causes numerous bubbles to form in the second diluent in the second diluent tank 75, and the oxygen-containing gas dissolves in the second diluent in the second diluent tank 75. While air such as dry air contains approximately 21 vol% oxygen, nitrogen gas contains no oxygen or only a very small amount of oxygen. Therefore, dissolving the oxygen-containing gas in the second diluent can increase the dissolved oxygen concentration in the second diluent.

[0110] The dissolved oxygen concentration of the second diluent is higher than that of the first diluent and higher than that of the stock solution. The dissolved oxygen concentration of the first diluent may be higher, lower, or equal to that of the stock solution. The dissolved oxygen concentration of the first diluent and that of the stock solution are, for example, 2 ppm or less. The dissolved oxygen concentration of the second diluent is, for example, 6 to 7 ppm. The dissolved oxygen concentration of the stock solution diluted only with the first diluent is, for example, 2 ppm or less. The dissolved oxygen concentration of the stock solution diluted only with the second diluent is a value between the dissolved oxygen concentrations of the stock solution and the second diluent.

[0111] If the dissolved oxygen concentration of the stock solution diluted only with the first diluent is defined as the first dissolved oxygen concentration, and the dissolved oxygen concentration of the stock solution diluted only with the second diluent is defined as the second dissolved oxygen concentration, then by diluting the stock solution with both the first and second diluents, it is possible to create an etching solution (stock solution diluted with the first and second diluents) whose dissolved oxygen concentration is between the first and second dissolved oxygen concentrations. Furthermore, by changing the ratio of the first and second diluents, it is possible to change the dissolved oxygen concentration of the etching solution between the first and second dissolved oxygen concentrations.

[0112] The first etching solution described below refers to an undiluted etching solution containing only the first diluent or diluted with both the first and second diluents. The second etching solution described below refers to an undiluted etching solution containing only the second diluent or diluted with both the first and second diluents. When both the first and second etching solutions contain the first and second diluents, the ratio of the first and second diluents is adjusted so that the dissolved oxygen concentration of the second etching solution is higher than that of the first etching solution.

[0113] FIG. 7 is a block diagram showing the electrical configuration of the substrate processing apparatus 1. As shown in FIG. The control device 3 is a computer including a computer main body 3a and a peripheral device 3d connected to the computer main body 3a. The computer main body 3a includes a CPU 3b (central processing unit) that executes various commands and a main memory device 3c that stores information. The peripheral device 3d includes an auxiliary memory device 3e that stores information such as a program P, a reading device 3f that reads information from removable media RM, and a communication device 3g that communicates with other devices such as a host computer.

[0114] The control device 3 is connected to an input device and a display device. The input device is operated when an operator such as a user or a maintenance technician inputs information into the substrate processing apparatus 1. The information is displayed on the screen of the display device. The input device may be any of a keyboard, a pointing device, and a touch panel, or may be other devices. The substrate processing apparatus 1 may be provided with a touch panel display that serves as both an input device and a display device.

[0115] The CPU 3b executes a program P stored in the auxiliary storage device 3e. The program P in the auxiliary storage device 3e may be pre-installed in the control device 3, may be sent from a removable medium RM to the auxiliary storage device 3e via a reading device 3f, or may be sent from an external device such as a host computer to the auxiliary storage device 3e via a communication device 3g.

[0116] The auxiliary storage device 3e and the removable medium RM are non-volatile memories that retain their memories even when power is not supplied. The auxiliary storage device 3e is, for example, a magnetic storage device such as a hard disk drive. The removable medium RM is, for example, an optical disk such as a compact disk or a semiconductor memory such as a memory card. The removable medium RM is an example of a computer-readable recording medium on which the program P is recorded. The removable medium RM is a non-transitory tangible recording medium.

[0117] The auxiliary storage device 3e stores a plurality of recipes. A recipe is information that specifies the processing content, processing conditions, and processing procedure of the substrate W. The plurality of recipes differ from one another in at least one of the processing content, processing conditions, and processing procedure of the substrate W. The control device 3 controls the substrate processing apparatus 1 so that the substrate W is processed in accordance with the recipe specified by the host computer. The control device 3 is programmed to execute each process described below.

[0118] 8 is a process diagram for explaining an example of processing of a substrate W performed by the substrate processing apparatus 1. In the following, reference will be made to FIGS. 1A, 2, 3, 6, and 8. FIG. When a substrate W is processed by the substrate processing apparatus 1, a loading step of loading the substrate W into the chamber 4 is performed (step S1 in FIG. 8). Specifically, with the lift frame 32 and the blocking member 33 in the upper position and all the guards 25 in the lower position, the center robot CR supports the substrate W with the hand H1 and causes the hand H1 to enter the chamber 4. Then, the center robot CR places the substrate W on the hand H1 on the multiple chuck pins 11 with the surface of the substrate W facing upward. The multiple chuck pins 11 are then pressed against the outer peripheral surface of the substrate W, thereby gripping the substrate W. After placing the substrate W on the spin chuck 10, the center robot CR retracts the hand H1 from the interior of the chamber 4.

[0119] Next, the upper gas valve 57 and the lower gas valve 21 are opened, and the upper central opening 38 of the blocking member 33 and the lower central opening 18 of the spin base 12 begin to discharge nitrogen gas. This reduces the oxygen concentration in the atmosphere in contact with the substrate W. Furthermore, the blocking member lifting unit 31 lowers the lifting frame 32 from the upper position to the lower position, and the guard lifting unit 27 raises one of the guards 25 from the lower position to the upper position. At this time, the spin base 12 is held at a reference rotation angle at which the multiple upper support parts 43 overlap the multiple lower support parts 44 in a plan view. Therefore, the upper support parts 43 of the blocking member 33 are supported by the lower support parts 44 of the spin base 12, and the blocking member 33 moves away from the lifting frame 32. Thereafter, the spin motor 14 is driven, and rotation of the substrate W begins (step S2 in FIG. 8).

[0120] Next, a chemical supplying step is performed in which DHF, an example of a chemical, is supplied to the upper surface of the substrate W (Step S3 in FIG. 8). Specifically, with the blocking member 33 in the lower position, the chemical liquid valve 51 is opened and the central nozzle 45 begins to discharge DHF. The DHF discharged from the central nozzle 45 collides with the center of the upper surface of the substrate W and then flows outward along the upper surface of the rotating substrate W. This forms a liquid film of DHF that covers the entire upper surface of the substrate W, and DHF is supplied to the entire upper surface of the substrate W. When a predetermined time has elapsed since the chemical liquid valve 51 was opened, the chemical liquid valve 51 is closed and the discharge of DHF is stopped.

[0121] Next, a first rinsing liquid supplying step is performed in which pure water, which is an example of a rinsing liquid, is supplied to the upper surface of the substrate W (Step S4 in FIG. 8). Specifically, with the blocking member 33 in the lower position, the upper rinse liquid valve 55 is opened and the central nozzle 45 starts to discharge pure water. The pure water that hits the center of the upper surface of the substrate W flows outward along the upper surface of the rotating substrate W. The DHF on the substrate W is washed away by the pure water discharged from the central nozzle 45. As a result, a liquid film of pure water is formed that covers the entire upper surface of the substrate W. When a predetermined time has elapsed since the upper rinse liquid valve 55 was opened, the upper rinse liquid valve 55 is closed and the discharge of pure water is stopped.

[0122] Next, a first etching step is performed in which a first etching liquid, which is an example of an etching liquid, is supplied to the upper surface of the substrate W (Step S5 in FIG. 8). Specifically, with the blocking member 33 in the lower position, the first valve V1 and the second valve V2 of the mixing valve 80 are opened, and the etching liquid valve 53 is opened. This causes the first etching liquid, i.e., the undiluted etching liquid diluted with the first diluent, to be supplied to the center nozzle 45, which then begins to discharge the first etching liquid. Before the discharge of the first etching liquid begins, the guard lifting unit 27 may vertically move at least one guard 25 to switch the guard 25 that receives the liquid discharged from the substrate W. The first etching liquid that collides with the center of the upper surface of the substrate W flows outward along the upper surface of the rotating substrate W. The deionized water on the substrate W is replaced with the first etching liquid discharged from the center nozzle 45. This forms a liquid film of the first etching liquid that covers the entire upper surface of the substrate W.

[0123] After the liquid film of the first etching liquid is formed, a second etching step is performed in which a second etching liquid, which is another example of an etching liquid, is supplied to the upper surface of the substrate W (Step S6 in FIG. 8). Specifically, while the first valve V1 of the mixing valve 80 and the etching liquid valve 53 remain open, the second valve V2 of the mixing valve 80 is closed and the third valve V3 of the mixing valve 80 is opened. At this time, the opening degree of the flow rate control valve 69 (see FIG. 6) may be changed as necessary. When the second valve V2 of the mixing valve 80 is closed and the third valve V3 of the mixing valve 80 is opened, the supply of the first diluent to the mixing valve 80 is stopped and the supply of the second diluent to the mixing valve 80 is started. As a result, the second etching liquid, i.e., the undiluted etching liquid diluted with the second diluent, is supplied to the center nozzle 45, and the center nozzle 45 starts to discharge the second etching liquid. Before the discharge of the second etching liquid starts, the guard lifting unit 27 may vertically move at least one guard 25 to switch the guard 25 that receives the liquid discharged from the substrate W.

[0124] With the blocking member 33 in the lower position, the second etching liquid is discharged from the central nozzle 45 toward the center of the upper surface of the substrate W. The second etching liquid that hits the center of the upper surface of the substrate W flows outward along the upper surface of the rotating substrate W. The first etching liquid on the substrate W is replaced with the second etching liquid discharged from the central nozzle 45. As a result, a liquid film of the second etching liquid is formed that covers the entire upper surface of the substrate W. Thereafter, all valves (first valve V1, second valve V2, and third valve V3) of the mixing valve 80 are closed, and the etching liquid valve 53 is closed. As a result, the discharge of the second etching liquid from the central nozzle 45 is stopped with the entire upper surface of the substrate W covered with a liquid film of the second etching liquid.

[0125] Next, a second rinsing liquid supplying step is performed in which pure water, which is an example of a rinsing liquid, is supplied to the upper surface of the substrate W (Step S7 in FIG. 8). Specifically, with the blocking member 33 in the lower position, the upper rinse liquid valve 55 is opened and the central nozzle 45 starts to discharge pure water. The pure water that hits the central portion of the upper surface of the substrate W flows outward along the upper surface of the rotating substrate W. The second etching liquid on the substrate W is washed away by the pure water discharged from the central nozzle 45. This forms a liquid film of pure water that covers the entire upper surface of the substrate W. When a predetermined time has elapsed since the upper rinse liquid valve 55 was opened, the upper rinse liquid valve 55 is closed and the discharge of pure water is stopped.

[0126] Next, a drying step is performed in which the substrate W is dried by rotating the substrate W (Step S8 in FIG. 8). Specifically, with the blocking member 33 in the lower position, the spin motor 14 accelerates the substrate W in the rotational direction, rotating the substrate W at a high rotational speed (e.g., several thousand rpm) that is higher than the rotational speed of the substrate W during the period from the chemical liquid supply step to the second rinse liquid supply step. This removes the liquid from the substrate W, and the substrate W is dried. When a predetermined time has elapsed since the high-speed rotation of the substrate W began, the spin motor 14 stops its rotation. At this time, the spin motor 14 stops the spin base 12 at the reference rotation angle. This stops the rotation of the substrate W (step S9 in FIG. 8).

[0127] Next, an unloading step is performed in which the substrate W is unloaded from the chamber 4 (step S10 in FIG. 8). Specifically, the shielding member lifting unit 31 lifts the lifting frame 32 to the upper position, and the guard lifting unit 27 lowers all of the guards 25 to the lower position. Furthermore, the upper gas valve 57 and the lower gas valve 21 are closed, and the upper central opening 38 of the shielding member 33 and the lower central opening 18 of the spin base 12 stop discharging nitrogen gas. The center robot CR then moves the hand H1 into the chamber 4. After the chuck pins 11 release their grip on the substrate W, the center robot CR supports the substrate W on the spin chuck 10 with the hand H1. The center robot CR then retracts the hand H1 from the interior of the chamber 4 while still supporting the substrate W with the hand H1. This causes the processed substrate W to be removed from the chamber 4.

[0128] Fig. 9A is a schematic view showing an example of a cross section of the substrate W before a first etching liquid is supplied in the example of processing the substrate W shown in Fig. 8. Fig. 9B is a schematic view showing an example of a cross section of the substrate W after a first etching liquid is supplied in the example of processing the substrate W shown in Fig. 8. Fig. 9C is a schematic view showing an example of a cross section of the substrate W after a second etching liquid is supplied in the example of processing the substrate W shown in Fig. 8.

[0129] When an acidic chemical solution such as DHF is supplied to the substrate W in the chemical solution supplying step (step S3 in FIG. 8), a native oxide film is removed from the surface of the substrate W. FIG. 9A shows an example of a cross section of the substrate W from which the native oxide film has been removed. The cross section of the substrate W shown in FIG. 9A is the same as the cross section of the substrate W before the acidic chemical solution is supplied to the substrate W. A recess 95 is formed on the surface of the substrate W before the acidic chemical solution is supplied. The recess 95 is recessed from the outermost surface of the substrate W in the thickness direction of the substrate W. The recess 95 may be a hole or a groove extending in the surface direction of the substrate W.

[0130] The width W1 of the recess 95 is smaller than the depth D1 of the recess 95. In other words, the maximum distance between the side surfaces 95s of the recess 95 is smaller than the length of the side surfaces 95s in the depth direction of the recess 95. Before the substrate W is processed in the substrate processing apparatus 1, the width W1 of the recess 95 may be constant from the entrance of the recess 95 to the bottom of the recess 95, or may vary. FIG. 9A shows an example in which the width W1 of the recess 95 continuously decreases as it approaches the bottom of the recess 95. This decrease in width W1 occurs not when an acidic chemical solution is supplied in the substrate processing apparatus 1, but in a pre-processing step, such as a dry etching step, performed before the substrate W is loaded into the substrate processing apparatus 1.

[0131] The width W1 of the recess 95 (or the maximum value if the width W1 of the recess 95 is not uniform) is, for example, 30 to 2000 nm. The depth D1 of the recess 95 is, for example, 60 to 4000 nm. The aspect ratio of the recess 95 (depth D1 of the recess 95 / width W1 of the recess 95) is, for example, 2 to 200. If the width W1 of the recess 95 continuously decreases toward the bottom of the recess 95, the difference between the maximum value of the width W1 of the recess 95 and the minimum value of the width W1 of the recess 95 is, for example, 1 to 200 nm.

[0132] FIG. 9A shows an example in which the entire side surface 95s of the recess 95 is formed of polysilicon, which is an example of the etching target 96. The entire side surface 95s of the recess 95 may be formed of the etching target 96, or only a portion of the side surface 95s may be formed of the etching target 96. In the latter case, it is sufficient that at least a portion of the upper portion of the side surface 95s and at least a portion of the lower portion of the side surface 95s are exposed. In this case, a portion of the side surface 95s may be formed of a material other than the etching target 96, and the remaining portion of the side surface 95s may be formed of the etching target 96. The upper portion of the side surface 95s is the portion above a position that bisects the side surface 95s in the depth direction of the recess 95. The lower portion of the side surface 95s is the portion below a position that bisects the side surface 95s in the depth direction of the recess 95.

[0133] When an acidic chemical solution is supplied to the substrate W in the chemical solution supplying step (step S3 in FIG. 8), the native oxide film of polysilicon, i.e., the silicon oxide film, is removed from the side surface 95s of the recess 95. Thereafter, a first etching solution, which is an alkaline etching solution with a low dissolved oxygen concentration, is supplied to the substrate W (step S5 in FIG. 8). Because the first etching solution has a low dissolved oxygen concentration, the polysilicon exposed on the side surface 95s of the recess 95 is unlikely to be oxidized by the dissolved oxygen in the first etching solution. Therefore, when the first etching solution is supplied to the substrate W, the side surface 95s of the recess 95 is uniformly etched at a high etching rate.

[0134] 9B shows the cross section of the substrate W after the acidic chemical solution has been supplied but before the first etching liquid has been supplied by a two-dot chain line, and the cross section of the substrate W after the first etching liquid has been supplied by a solid line. The width W1 of the recess 95 continuously decreases as it approaches the bottom of the recess 95, and the side surface 95s of the recess 95 is uniformly etched by the supply of the first etching liquid, so the width W1 of the recess 95 continuously decreases as it approaches the bottom of the recess 95 even after the first etching liquid has been supplied.

[0135] After the first etching liquid is supplied to the substrate W, a second etching liquid, which is an alkaline etching liquid having a higher dissolved oxygen concentration than the first etching liquid, is supplied to the substrate W (step S6 in FIG. 8). As a result, all or almost all of the first etching liquid in contact with the substrate W is replaced with the second etching liquid, and the second etching liquid enters the recess 95. In FIG. 9C, the cross section of the substrate W after the first etching liquid has been supplied but before the second etching liquid has been supplied is shown by a two-dot chain line, and the cross section of the substrate W after the second etching liquid has been supplied is shown by a solid line.

[0136] As shown in FIG. 9C, when the second etching liquid is supplied to the recess 95, dissolved oxygen (O2 in FIG. 9) contained in the second etching liquid comes into contact with the side surface 95s of the recess 95 near the entrance of the recess 95, oxidizing polysilicon, which is an example of the etching target 96. Therefore, the second etching liquid with a reduced dissolved oxygen concentration flows, albeit slightly, toward the bottom of the recess 95. Even at a distance from the entrance of the recess 95, the dissolved oxygen in the second etching liquid comes into contact with the side surface 95s of the recess 95 and is consumed. This phenomenon is continuously repeated, and as a result, the dissolved oxygen concentration in the second etching liquid continuously decreases as it approaches the bottom of the recess 95.

[0137] Because the second etching solution has a relatively high dissolved oxygen concentration, when the second etching solution is supplied to the substrate W, the side surface 95s of the recess 95 is oxidized by the dissolved oxygen in the second etching solution. As described above, the dissolved oxygen concentration in the second etching solution decreases toward the bottom of the recess 95. For a given depth position of the recess 95, the side surface 95s of the recess 95 is uniformly oxidized. However, the amount of oxidation of the side surface 95s of the recess 95 decreases toward the bottom of the recess 95. When polysilicon is oxidized, it is converted into silicon oxide, which is resistant to corrosion by alkaline etching solutions. When single-crystal silicon and amorphous silicon are oxidized, they are also converted into silicon oxide. Therefore, as can be seen by comparing the solid line and the two-dot chain line in Figure 9C, the amount of etching of the side surface 95s of the recess 95 increases toward the bottom of the recess 95.

[0138] Since the amount of etching of the side surface 95s of the recess 95 increases as it approaches the bottom of the recess 95, even if the width W1 of the recess 95 continuously decreases as it approaches the bottom of the recess 95 before the substrate W is processed in the substrate processing apparatus 1, after the second etching liquid is supplied, the width W1 of the recess 95 becomes uniform from the entrance of the recess 95 to the bottom of the recess 95, or the non-uniformity of the width W1 of the recess 95 is reduced. Therefore, even if the shape of the recess 95 when it is carried into the substrate processing apparatus 1 is different from the intended shape, after the second etching liquid is supplied, the shape of the recess 95 can be made to match or approach the intended shape.

[0139] In this way, by supplying an alkaline etching solution with a low dissolved oxygen concentration to the recess 95, the side surface 95s of the recess 95 can be uniformly etched from the entrance of the recess 95 to the bottom of the recess 95. On the other hand, by supplying an alkaline etching solution with a relatively high dissolved oxygen concentration to the recess 95, the amount of etching of the side surface 95s of the recess 95 can be increased as the depth approaches the bottom of the recess 95. In this case, by changing the dissolved oxygen concentration, the rate of change in the amount of etching can be increased or decreased. Therefore, by changing the dissolved oxygen concentration of the etching solution, the shape of the recess 95 after etching can be controlled.

[0140] Fig. 10A is a schematic view showing another example of a cross section of the substrate W before the first etching liquid is supplied in the example of processing the substrate W shown in Fig. 8. Fig. 10B is a schematic view showing another example of a cross section of the substrate W after the first etching liquid is supplied in the example of processing the substrate W shown in Fig. 8. Fig. 10C is a schematic view showing another example of a cross section of the substrate W after the second etching liquid is supplied in the example of processing the substrate W shown in Fig. 8.

[0141] 10A to 10C, polysilicon films P1 to P3, which are an example of an object to be etched 96, and silicon oxide films O1 to O3, which are an example of an object not to be etched, are exposed on a side surface 95s of the recess 95. The polysilicon films P1 to P3 and the silicon oxide films O1 to O3 are alternately stacked, and the recess 95 penetrates these films in the thickness direction of the substrate W. 10B, the cross section of the substrate W after the supply of an acidic chemical solution such as DHF but before the supply of the first etching liquid is shown by a two-dot chain line, and the cross section of the substrate W after the supply of the first etching liquid is shown by a solid line. The supply of the first etching liquid causes the polysilicon films P1 to P3 to be uniformly etched. At this time, the silicon oxide films O1 to O3 are also slightly etched.

[0142] After the first etching liquid is supplied to the substrate W, a second etching liquid, which is an alkaline etching liquid having a higher dissolved oxygen concentration than the first etching liquid, is supplied to the substrate W. As a result, all or almost all of the first etching liquid in contact with the substrate W is replaced with the second etching liquid. In Fig. 10C, the cross section of the substrate W after the first etching liquid has been supplied but before the second etching liquid has been supplied is shown by a two-dot chain line, and the cross section of the substrate W after the second etching liquid has been supplied is shown by a solid line.

[0143] 10C, when the second etching liquid is supplied to the substrate W, dissolved oxygen (see O2 in FIG. 9) contained in the second etching liquid comes into contact with the polysilicon film P1 and the silicon oxide film O1 located near the entrance of the recess 95, oxidizing the polysilicon film P1. Therefore, the second etching liquid with a reduced dissolved oxygen concentration flows, albeit slightly, toward the polysilicon film P2. As a result of this phenomenon being continuously repeated, the dissolved oxygen concentration of the second etching liquid continuously decreases as it approaches the bottom of the recess 95.

[0144] The dissolved oxygen concentration in the second etching solution decreases as one approaches the polysilicon film P3 located at the bottom of the recess 95. If the depth of the recess 95 is the same, the polysilicon films P1 to P3 are uniformly oxidized. However, the amount of oxidation of the polysilicon films P1 to P3 decreases as one approaches the bottom of the recess 95. When polysilicon is oxidized, it changes to silicon oxide, which is resistant to corrosion by alkaline etching solutions. When single-crystal silicon and amorphous silicon are oxidized, they also change to silicon oxide. Therefore, as can be seen by comparing the solid line and the two-dot chain line in FIG. 10C, the amount of etching of the polysilicon films P1 to P3 increases as one approaches the bottom of the recess 95.

[0145] Since the etching amount increases toward the polysilicon film P3, even if the shape of the polysilicon films P1 to P3 when they are brought into the substrate processing apparatus 1 is different from the intended shape, after the second etching liquid is supplied, the shape of the polysilicon films P1 to P3 can be deformed to or made closer to the intended shape. As described above, in the first embodiment, an alkaline first etching liquid having an inert gas dissolved therein is supplied to the substrate W. This etches the side surface 95s of the recess 95 formed in the substrate W. Similarly, an alkaline second etching liquid having an oxygen-containing gas dissolved therein, which is an example of a dissolved gas, is supplied to the substrate W. This etches the side surface 95s of the recess 95. Therefore, the side surface 95s of the recess 95 is etched stepwise by the supply of the first etching liquid and the supply of the second etching liquid.

[0146] An etching object 96 representing at least one of single crystal silicon, polysilicon, and amorphous silicon is exposed at least a portion of an upper part of a side surface 95s of the recess 95 and at least a portion of a lower part of the side surface 95s of the recess 95. When a liquid with a high concentration of dissolved oxygen is supplied to the etching object 96, the surface layer of the etching object 96 is converted into silicon oxide. Silicon oxide is not etched, or is barely etched, by an alkaline etching solution.

[0147] The dissolved oxygen that was present in the first etching liquid is removed from the first etching liquid by dissolving the inert gas. Because the dissolved oxygen concentration in the first etching liquid is low, even when the first etching liquid comes into contact with the etching object 96, the etching object 96 is not oxidized or is hardly oxidized. Therefore, by supplying the first etching liquid to the substrate W, the etching object 96 exposed on the side surface 95s of the recess 95 can be etched uniformly at a high etching rate.

[0148] On the other hand, because the dissolved oxygen concentration in the second etching liquid is higher than that in the first etching liquid, when the second etching liquid comes into contact with the etching object 96, the surface layer of the etching object 96 is oxidized and changes into silicon oxide that is resistant to corrosion by the second etching liquid. However, the entire surface layer of the etching object 96 is not oxidized uniformly, but is oxidized unevenly.

[0149] That is, because the width W1 of the recess 95 is narrow, when the second etching liquid is supplied to the recess 95, the dissolved oxygen contained in the second etching liquid comes into contact with the etching object 96 near the entrance of the recess 95 and oxidizes the etching object 96. Therefore, the second etching liquid with a reduced dissolved oxygen concentration flows, albeit slightly, toward the bottom of the recess 95. Even at a short distance from the entrance of the recess 95, the dissolved oxygen in the second etching liquid comes into contact with the etching object 96 and is consumed. As a result of this phenomenon being continuously repeated, the dissolved oxygen concentration in the second etching liquid decreases as it approaches the bottom of the recess 95.

[0150] If the depth of the recess 95 is the same, the etching target 96 is uniformly etched by the second etching liquid. However, the etching amount of the etching target 96 increases as one approaches the bottom of the recess 95. That is, near the entrance of the recess 95, the surface layer of the etching target 96 has changed to silicon oxide, and therefore the etching target 96 is difficult to etch by the second etching liquid. On the other hand, near the bottom of the recess 95, the surface layer of the etching target 96 has not changed to silicon oxide or has changed very little, so the etching target 96 is etched by the second etching liquid. Therefore, the etching amount of the etching target 96 near the bottom of the recess 95 is greater than the etching amount of the etching target 96 near the entrance of the recess 95.

[0151] In this way, by supplying the first etching liquid to the substrate W, the etching object 96 exposed on the side surface 95s of the recess 95 can be uniformly etched at a high etching rate. Furthermore, by supplying the second etching liquid to the substrate W, the etching object 96 can be etched so that the etching amount increases stepwise or continuously as the etching approaches the bottom of the recess 95. Therefore, by separately supplying the first etching liquid and the second etching liquid to the substrate W, the side surface 95s of the recess 95 can be intentionally etched non-uniformly while suppressing an increase in processing time.

[0152] In this embodiment, a first etching liquid having a low dissolved oxygen concentration is supplied to the substrate W, and then a second etching liquid having a relatively high dissolved oxygen concentration is supplied to the substrate W. If the second etching liquid is supplied to the substrate W first, the etching object 96 exposed on the side surface 95s of the recess 95 is oxidized. Therefore, when the first etching liquid is supplied, the etching object 96 is etched non-uniformly or the etching rate is reduced. By supplying the first etching liquid first, the processing time can be shortened compared to when the second etching liquid is supplied first, and the actual shape of the etched etching object 96 can be made closer to the intended shape.

[0153] In this embodiment, after the first etching liquid is supplied to the substrate W, the second etching liquid is supplied to the substrate W, rather than supplying a liquid other than the second etching liquid to the substrate W. This causes the first etching liquid in contact with the substrate W to be replaced with the second etching liquid. If a liquid other than the second etching liquid is supplied to the substrate W before the second etching liquid is supplied, the etching target 96 exposed on the side surface 95s of the recess 95 may be oxidized in an unintended manner. By replacing the first etching liquid in contact with the substrate W with the second etching liquid, such oxidation can be suppressed or prevented, and the etching target 96 can be etched with precision.

[0154] In this embodiment, the recess 95, which narrows toward the bottom of the recess 95, is etched with a first etching liquid and a second etching liquid. When the first etching liquid is supplied, the etching target 96 exposed at the side surface 95s of the recess 95 is uniformly etched, and when the second etching liquid is supplied, the etching amount of the etching target 96 increases toward the bottom of the recess 95. After the first etching liquid and the second etching liquid are supplied, the width W1 of the recess 95 becomes uniform from the entrance to the bottom of the recess 95, or non-uniformity in the width W1 of the recess 95 is reduced. Therefore, even if the width W1 of the recess 95 before etching is non-uniform, the shape of the recess 95 can be adjusted.

[0155] Polysilicon is composed of many single crystals of silicon. When polysilicon is etched with an alkaline etching solution that does not contain any compounds, extremely fine irregularities are formed on the surface of the polysilicon. This is because the (110), (100), and (111) faces of silicon are exposed on the surface of the polysilicon, and the etching rates of the (110), (100), and (111) faces of silicon are different from one another. When single crystal silicon is etched, extremely fine irregularities are formed on the surface of the single crystal silicon for the same reason.

[0156] Hydroxide ions (OH) in alkaline etching solutions -) reacts with silicon (Si) and etches the etching target 96, such as polysilicon. Adding the compound to an alkaline etching solution inhibits contact between hydroxide ions and silicon, slowing down the etching rates of the (110), (100), and (111) silicon faces. However, the etching rate does not decrease uniformly across multiple crystal faces, but rather decreases more significantly for those faces with higher etching rates. This reduces the difference in etching rate across multiple crystal faces.

[0157] In this way, adding a compound to the alkaline etching solution reduces the anisotropy of the etching solution with respect to the etching target 96, such as polysilicon. In other words, the etching of the etching target 96 approaches isotropic etching, and the etching target 96 is etched at a uniform etching rate at every location. This reduces the dependence of the etching rate on the surface orientation. Therefore, the occurrence of the above-mentioned unevenness can be suppressed or prevented, and the surface of the etching target 96 can be flattened after etching.

[0158] Next, a second embodiment will be described. The main difference between the first and second embodiments is that the substrate processing apparatus 101 is a batch type apparatus that processes a plurality of substrates W at once. Fig. 11 is a schematic diagram showing an etching unit 104 provided in a substrate processing apparatus 101 according to a second embodiment of the present invention. In Fig. 11, the same reference numerals as in Fig. 1 and the like are used to designate the same components as those shown in Figs. 1 to 10C, and descriptions thereof will be omitted.

[0159] The substrate processing apparatus 101 includes a plurality of processing units that process a plurality of substrates W collectively, a transport unit that performs a load operation for loading the plurality of substrates W into the processing units and an unload operation for unloading the plurality of substrates W from the processing units, and a control device 3 that controls the substrate processing apparatus 101. The plurality of processing units includes an etching unit 104 that simultaneously supplies an etching liquid to the plurality of substrates W. Although not shown, the plurality of processing units further includes a rinse liquid processing unit that simultaneously supplies a rinse liquid to the plurality of substrates W that have been supplied with the etching liquid, and a drying processing unit that simultaneously dries the plurality of substrates W that have been supplied with the rinse liquid.

[0160] The etching unit 104 includes an immersion tank 105 that stores an etching solution and into which multiple substrates W are simultaneously loaded. The transport unit includes a holder 103 that holds multiple substrates W in a vertical position, and a lifter 102 that raises and lowers the holder 103 between a lower position where the multiple substrates W held by the holder 103 are immersed in the etching solution in the immersion tank 105 and an upper position where the multiple substrates W held by the holder 103 are located above the etching solution in the immersion tank 105.

[0161] The etching unit 104 further includes a plurality of etching solution nozzles 106 each having an etching solution outlet through which an etching solution is discharged, and a plurality of gas nozzles 114 each having a gas outlet through which an inert gas is discharged. Each of the etching solution nozzles 106 and the gas nozzles 114 is cylindrical and extends horizontally within the immersion tank 105. The etching solution nozzles 106 and the gas nozzles 114 are arranged horizontally and parallel to each other. One or more gas nozzles 114 are arranged between two adjacent etching solution nozzles 106. When the holder 103 is located in the lower position (the position shown in FIG. 11 ), the etching solution nozzles 106 and the gas nozzles 114 are located below the substrates W held by the holder 103.

[0162] The etching liquid pipe 107 is connected to the plurality of etching liquid nozzles 106. The etching liquid pipe 107 includes a common pipe 107c that guides the etching liquid supplied to the plurality of etching liquid nozzles 106, and a plurality of branch pipes 107d that supply the etching liquid supplied from the common pipe 107c to the plurality of etching liquid nozzles 106. The common pipe 107c is connected to the mixing valve 80. An etching liquid valve 108 is interposed in the common pipe 107c. The plurality of branch pipes 107d branch off from the common pipe 107c. The plurality of branch pipes 107d are each connected to a plurality of etching liquid nozzles 106. Although FIG. 11 illustrates the branch pipes 107d as being connected to only the two etching liquid nozzles 106 on both sides, the branch pipes 107d are also connected to the other etching liquid nozzles 106.

[0163] The gas pipe 115 is connected to a plurality of gas nozzles 114. The gas pipe 115 includes a common pipe 115c that guides gas supplied to the plurality of gas nozzles 114 and a plurality of branch pipes 115d that supply gas supplied from the common pipe 115c to the plurality of gas nozzles 114. The common pipe 115c is connected to an inert gas supply source. A gas valve 116 and a flow rate control valve 117 are interposed in the common pipe 115c. The plurality of branch pipes 115d branch off from the common pipe 115c. The plurality of branch pipes 115d are respectively connected to a plurality of gas nozzles 114. Although FIG. 11 illustrates the branch pipes 115d as being connected to only two gas nozzles 114 on both sides, the branch pipes 115d are also connected to the other gas nozzles 114.

[0164] The etching unit 104 includes an overflow tank 113 that receives the etching solution that overflows from the immersion tank 105. The upstream end of a return pipe 112 is connected to the overflow tank 113, and the downstream end of the return pipe 112 is connected to a common pipe 107c of the etching solution pipe 107 at a position downstream of the etching solution valve 108. The etching solution that overflows from the immersion tank 105 into the overflow tank 113 is sent again to the multiple etching solution nozzles 106 by a pump 109 and is filtered by a filter 111 before reaching the multiple etching solution nozzles 106. The etching unit 104 may include a temperature regulator 110 that changes the temperature of the etching solution in the immersion tank 105 by heating or cooling the etching solution.

[0165] When the etching solution is discharged from the plurality of etching solution nozzles 106, the etching solution is supplied into the immersion tank 105, and an upward flow of the etching solution is formed in the etching solution in the immersion tank 105. The etching solution that overflows from an opening provided at the top end of the immersion tank 105 is received in the overflow tank 113 and returns to the plurality of etching solution nozzles 106 via the return pipe 112. This circulates the etching solution. On the other hand, when a drain valve 119 provided in the drain pipe 118 is opened, the liquid in the immersion tank 105, such as the etching solution, is discharged into the drain pipe 118. When supplying first and second alkaline etching liquids having different dissolved oxygen concentrations to multiple substrates W held in a holder 103, the first etching liquid is supplied to the immersion tank 105 through the multiple etching liquid nozzles 106 with the drain valve 119 closed. When a predetermined time has elapsed since the supply of the first etching liquid began, the drain valve 119 is opened to discharge the first etching liquid from the immersion tank 105. Thereafter, with the drain valve 119 closed, the second etching liquid is supplied to the immersion tank 105 through the multiple etching liquid nozzles 106.

[0166] The first etching liquid and the second etching liquid may be mixed in the immersion tank 105. For example, the supply of the first etching liquid may be stopped after a predetermined time has elapsed since the supply of the first etching liquid was started, and the supply of the second etching liquid may be subsequently started. In this case, the first etching liquid and the second etching liquid are mixed in the immersion tank 105, and the dissolved oxygen concentration of the etching liquid supplied to the substrate W is changed.

[0167] Instead of sequentially supplying the first etching liquid and the second etching liquid to one immersion tank 105, an immersion tank 105 storing the first etching liquid and an immersion tank 105 storing the second etching liquid may be provided, and the multiple substrates W constituting one batch may be sequentially carried into these two immersion tanks 105. In this way, it is possible to omit the need to change the etching liquid from the first etching liquid in the immersion tank 105 to the second etching liquid.

[0168] Other embodiments The present invention is not limited to the contents of the above-described embodiment, and various modifications are possible. For example, in the first embodiment, the etching liquid may be supplied to the lower surface of the substrate W instead of the upper surface of the substrate W. Alternatively, the etching liquid may be supplied to both the upper and lower surfaces of the substrate W. In these cases, the etching liquid may be discharged from the lower surface nozzle 15.

[0169] In the first embodiment, the first etching liquid and the second etching liquid may be ejected from separate nozzles. Alternatively, at least two of the undiluted etching liquid, the first diluted liquid, and the second diluted liquid may be ejected from separate nozzles and mixed in the space between the upper surface of the substrate W and the nozzles. In the first embodiment, a first etching liquid tank for storing the first etching liquid and a second etching liquid tank for storing the second etching liquid may be provided. In this case, the first etching liquid and the second etching liquid may be ejected toward the substrate W from the same nozzle, or may be ejected toward the substrate W from separate nozzles.

[0170] In the first embodiment, instead of replacing the first etching liquid on the substrate W with the second etching liquid, the first etching liquid on the substrate W may be replaced with a liquid (intermediate liquid) other than the second etching liquid, and then the intermediate liquid on the substrate W may be replaced with the second etching liquid. Alternatively, two or more types of liquid may be sequentially supplied to the substrate W between the supply of the first etching liquid and the supply of the second etching liquid. For example, the first etching liquid on the substrate W may be replaced with the first intermediate liquid, the first intermediate liquid on the substrate W may be replaced with the second intermediate liquid, and the second intermediate liquid on the substrate W may be replaced with the second etching liquid.

[0171] In the first and second embodiments, the first etching liquid may be supplied to the substrate W after the second etching liquid is supplied to the substrate W. In this case, the second etching liquid and the first etching liquid may be supplied to the substrate W consecutively, or a liquid other than the first etching liquid may be supplied to the substrate W before the first etching liquid is supplied. In the first and second embodiments, the compound contained in the first etching solution may be different from the compound contained in the second etching solution.

[0172] In the first and second embodiments, at least one of the first etching liquid and the second etching liquid may be an alkaline etching liquid that does not contain the above-mentioned compound. In this case, the above-mentioned compound may be mixed into the alkaline etching liquid that does not contain the compound before or after the alkaline etching liquid that does not contain the compound is supplied to the substrate W. For example, the alkaline etching liquid that does not contain the compound and a compound-containing liquid that contains the compound may be mixed on the front or back surface of the substrate W.

[0173] The cylindrical portion 37 may be omitted from the blocking member 33. The upper support portion 43 and the lower support portion 44 may be omitted from the blocking member 33 and the spin chuck 10. The blocking member 33 may be omitted from the processing unit 2. In this case, the processing unit 2 may be provided with a nozzle that ejects a processing liquid such as a chemical solution toward the substrate W. The nozzle may be a scan nozzle that is horizontally movable within the chamber 4, or a fixed nozzle that is fixed to the partition wall 6 of the chamber 4. The nozzle may have multiple liquid ejection ports that simultaneously eject the processing liquid toward multiple positions that are spaced apart in the radial direction of the substrate W, thereby supplying the processing liquid to the upper or lower surface of the substrate W. In this case, at least one of the flow rate, temperature, and concentration of the ejected processing liquid may be changed for each liquid ejection port.

[0174] The substrate processing apparatus 1 is not limited to an apparatus for processing a disk-shaped substrate W, but may be an apparatus for processing a polygonal substrate W. Any two or more of the above-mentioned features may be combined. Any two or more of the above-mentioned steps may be combined. In addition, various design modifications can be made within the scope of the claims. [Explanation of symbols]

[0175] 1: Substrate processing equipment 61: Processing liquid supply unit (first and second etching means) 95: Recess 95s: Side of recess 96: Etching object D1: Depth of recess W: Substrate W1: Recess width

Claims

1. A substrate processing method for processing a substrate having a recess formed thereon, the recess having a width shorter than a depth, and an etching target representing at least one of single crystal silicon, polysilicon, and amorphous silicon, exposed at least a part of an upper part of a side surface and at least a part of a lower part of the side surface, the method comprising: a first etching step of etching the etching target exposed on the side surface of the recess by supplying to the substrate a first alkaline etching solution prepared by diluting an etching stock solution with a first diluting solution having a first dissolved oxygen concentration stored in a first diluting solution tank; a second etching step of etching the etching object exposed on the side surface of the recess by supplying to the substrate a second alkaline etching solution prepared by diluting the undiluted etching solution with a second diluting solution having a second dissolved oxygen concentration higher than the first dissolved oxygen concentration stored in a second diluting solution tank.

2. 2. The substrate processing method according to claim 1, wherein the second etching step is a step of supplying the second etching liquid to the substrate after the first etching liquid has been supplied to the substrate.

3. 3. The substrate processing method according to claim 2, wherein the second etching step includes a step of supplying the second etching liquid to the substrate, thereby replacing the first etching liquid in contact with the substrate with the second etching liquid.

4. a width of the recess before the first etching liquid and the second etching liquid are supplied decreases toward a bottom of the recess, 4. The substrate processing method according to claim 1, wherein the second etching step is a step of etching the side surface of the recess so that the etching amount of the side surface of the recess increases as the depth approaches the bottom of the recess.

5. 5. The substrate processing method according to claim 1, wherein at least one of the first etching solution and the second etching solution is an alkaline etching solution containing a compound that inhibits contact between hydroxide ions and the object to be etched.

6. 6. The substrate processing method according to claim 5, wherein the concentration of said compound in said alkaline etching solution is set according to a required etching uniformity and a required etching rate.

7. 7. The substrate processing method according to claim 1, wherein the substrates are processed one by one.

8. 7. The substrate processing method according to claim 1, wherein a plurality of the substrates are processed at once.

9. A substrate processing apparatus for processing a substrate having an etching target having a width smaller than a depth and representing at least one of single crystal silicon, polysilicon, and amorphous silicon, and a recess formed therein, the recess being exposed at least part of an upper portion of a side surface and at least part of a lower portion of the side surface, a first etching means for etching the etching object exposed on the side surface of the recess by supplying to the substrate a first alkaline etching solution prepared by diluting an undiluted etching solution with a first diluting solution having a first dissolved oxygen concentration stored in a first diluting solution tank; and a second etching means for etching the etching object exposed on the side surface of the recess by supplying to the substrate a second alkaline etching solution prepared by diluting the undiluted etching solution with a second diluting solution having a second dissolved oxygen concentration higher than the first dissolved oxygen concentration and stored in a second diluting solution tank.

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