Substrate processing method

Abstract

To provide a substrate processing method enabling etching depth to be highly accurately controlled.SOLUTION: A substrate processing method is used for processing a substrate having a main surface from which at least one of a silicon oxide layer and silicon nitride layer are exposed as a processing object layer. The substrate processing method includes: an etchant supply step of supplying an etchant containing an ammonium monohydrodifluoride as an etchant agent for etching to the processing object layer of the main surface of the substrate; a heating step of heating the etchant on the main surface of the substrate after the etchant supply step; and a rinse liquid supply step of supplying a rinse liquid onto the main surface of the substrate after the heating step.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a substrate processing method 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] The following Patent Document 1 discloses a substrate processing method for etching a substrate having a dielectric layer using a process gas including a fluorocarbon gas containing a first group of fluorocarbons containing hydrogen (e.g., CHF3) and a second group of fluorocarbons not containing hydrogen (e.g., C4F8), a carbon-oxygen containing gas such as CO, and a nitrogen containing gas such as N2. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-41274 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 discloses that the above-described substrate processing can achieve high selectivity etching. However, in the substrate processing disclosed in Patent Document 1, it is difficult to stop the reaction between the process gas and the substrate at a desired etching depth. Therefore, one object of the present invention is to provide a substrate processing method that can accurately control the etching depth. [Means for solving the problem]

[0005] One embodiment of the present invention provides a substrate processing method for processing a substrate having a main surface in which at least one of a silicon oxide layer and a silicon nitride layer is exposed as a processing target layer, the substrate processing method including: an etching solution supplying step of supplying an etching solution containing ammonium fluoride as an etchant for etching the processing target layer to the main surface of the substrate after the etching solution supplying step; a heating step of heating the etching solution on the main surface of the substrate after the etching solution supplying step; and a rinsing solution supplying step of supplying a rinsing solution to the main surface of the substrate after the heating step.

[0006] According to this method, the target layer is at least one of a silicon oxide layer and a silicon nitride layer, and the etching solution contains ammonium fluoride as an etching agent. Therefore, heating can rapidly react the target layer with the etching agent present on the main surface of the substrate, reducing the time dependency of etching of the target layer. In other words, saturated atomic layer etching can be achieved.

[0007] Saturated atomic layer etching is an etching process that stops after a certain process time, allowing the etching depth to be controlled. By repeating saturated atomic layer etching multiple times, the desired etching depth can be easily achieved. Specifically, one cycle stops within a few tens of seconds, and an etching depth of several nanometers to several tens of nanometers can be achieved.

[0008] In one embodiment of the present invention, the substrate processing method further includes a rotation step of rotating the substrate around a central axis passing through a center of the main surface of the substrate after stopping the supply of the etching solution to the main surface of the substrate in the etching solution supply step and before the heating step.

[0009] According to this method, the supply of the etching solution to the main surface of the substrate is stopped, and then the substrate is rotated. This allows the amount of etching solution on the main surface of the substrate to be appropriately reduced, thereby controlling the total amount of etching agent present on the main surface of the substrate. Controlling the total amount of etching agent makes it easier to control the amount of etching of the target layer. In particular, by rotating the substrate at a rotation speed of 2000 rpm or more and 4000 rpm or less, the total amount of etching agent present on the main surface of the substrate can be accurately controlled.

[0010] In one embodiment of the present invention, the mass percent concentration of the etching agent in the etching solution supplied to the main surface of the substrate is 0.2 wt% or more and less than 10 wt%. If the mass percent concentration of the etching agent in the etching solution is 0.2 wt% or more and less than 10 wt%, saturated atomic layer etching is easily achieved.

[0011] In one embodiment of the present invention, in the heating step, the substrate is heated to a temperature of 50° C. or higher and 200° C. or lower. If the heating temperature of the etching solution is 50° C. or higher and 200° C. or lower, the layer to be processed and the etching agent present on the main surface of the substrate can react particularly quickly.

[0012] In one embodiment of the present invention, the etching depth of the target layer is proportional to the total amount of the etching agent in the etching solution present on the main surface of the substrate at the start of the heating step, and therefore, by controlling the amount of etching solution present on the main surface of the substrate at the start of the heating step, the etching depth can be controlled with high precision.

[0013] In one embodiment of the present invention, the heating step includes a reaction promotion step of promoting the reaction between the etching agent in the etching solution on the main surface of the substrate and the layer to be treated by removing, by heating, a solid layer formed on the layer to be treated by a reaction between the etching agent and the layer to be treated.

[0014] According to this method, the solid layer formed by the reaction between the etching agent and the target layer is removed by heating, which accelerates the reaction between the etching agent and the target layer, thereby enabling the target layer to react more quickly with the etching agent present on the main surface of the substrate.

[0015] In one embodiment of the present invention, the substrate may further include an insulating layer, a channel formed by digging into the surface of the insulating layer and in which the layer to be processed is buried, and a covering layer interposed between the layer to be processed and a sidewall of the channel and covering the sidewall of the channel. The substrate may also include a semiconductor layer and a plurality of structures formed on the semiconductor layer, with the layer to be processed located between the structures. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic plan view showing the layout of a substrate processing apparatus according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram for explaining the configuration of a wet processing unit provided in the substrate processing apparatus. [Figure 3] FIG. 3 is a block diagram for explaining the electrical configuration of the substrate processing apparatus. [Figure 4] FIG. 4 is a flowchart for explaining the substrate processing performed by the substrate processing apparatus. [Figure 5] FIG. 5 is a schematic diagram for explaining the state of the upper surface of the substrate during the substrate processing. [Figure 6] FIG. 6 is a schematic diagram for explaining an example of a mechanism for etching a processing target layer exposed from the upper surface of a substrate. [Figure 7A] FIG. 7A is a schematic diagram illustrating an example of the structure of a surface layer portion of the upper surface of a substrate processed in the substrate processing apparatus. [Figure 7B]FIG. 7B is a schematic diagram for explaining a change in structure due to etching of the surface layer portion of the upper surface of the substrate shown in FIG. 7A. [Figure 8A] FIG. 8A is a schematic diagram for explaining another example of the structure of the surface layer portion of the upper surface of the substrate processed in the substrate processing apparatus. [Figure 8B] FIG. 8B is a schematic diagram for explaining a change in structure due to etching of the surface layer portion of the upper surface of the substrate shown in FIG. 8A. [Figure 9] FIG. 9 is a schematic diagram for explaining a modified example of the wet processing unit. [Figure 10] FIG. 10 is a schematic plan view showing the layout of a substrate processing apparatus according to a second embodiment of the present invention. [Figure 11] FIG. 11 is a schematic view for explaining the configuration of a wet processing unit provided in a substrate processing apparatus according to the second embodiment. [Figure 12] FIG. 12 is a schematic view for explaining the configuration of a dry processing unit provided in a substrate processing apparatus according to the second embodiment. [Figure 13A] FIG. 13A is a schematic diagram for explaining the procedure of a time change experiment for observing the time dependency of etching. [Figure 13B] FIG. 13B is a graph showing the results of the time course experiment. [Figure 14] FIG. 14 is a graph showing the results of a concentration change experiment for observing the concentration dependency of etching. [Figure 15] FIG. 15 is a table showing the results of a crystal observation experiment for observing the generation of crystals in an etching solution. [Figure 16] FIG. 16 is a graph showing the results of an experiment to change the rotation speed to observe the dependency of etching on the substrate rotation speed. [Figure 17] FIG. 17 is a graph showing the results of a temperature change experiment for observing the heating temperature dependency of etching. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0018] <Configuration of the Substrate Processing Apparatus According to the First Embodiment> FIG. 1 is a schematic plan view showing the layout of a substrate processing apparatus 1 according to a first embodiment of the present invention.

[0019] The substrate processing apparatus 1 is a single-wafer processing apparatus that processes substrates W one by one. In this embodiment, the substrate W has a circular shape. The substrate W has a pair of main surfaces. At least one of the pair of main surfaces of the substrate W exposes at least one of a silicon oxide layer (SiO2 layer) and a silicon nitride layer (SiN layer) as a processing target layer. The substrate processing apparatus 1 includes a plurality of processing units 2 that process the substrates W, a load port LP on which carriers C are placed that accommodate a plurality of substrates W to be processed in the processing units 2, transport robots IR and CR that transport the substrates W between the load port LP and the processing units 2, and a controller 3 that controls the substrate processing apparatus 1.

[0020] The transport robot IR transports the substrate W between the carrier C and the transport robot CR. The transport robot CR transports the substrate W between the transport robot IR and the processing unit 2. The transport robots IR and CR are arranged on a transport path TR that extends from a plurality of load ports LP toward a plurality of processing units 2.

[0021] The multiple processing units 2 have, for example, the same configuration. The multiple processing units 2 form four processing towers TW arranged at four horizontally spaced positions. Each processing tower TW includes multiple (for example, three) processing units 2 stacked vertically. The four processing towers TW are arranged two on each side of the transport path TR.

[0022] The processing unit 2 is a wet processing unit 2W that uses a processing liquid to process the substrate W. As will be described in detail later, examples of the processing liquid supplied to the substrate W in the wet processing unit 2W include an etching liquid and a rinse liquid.

[0023] Each wet processing unit 2W includes a processing cup 7 and a chamber 4 that houses the processing cup 7. The chamber 4 is formed with an entrance (not shown) through which the transfer robot CR loads and unloads the substrate W. The chamber 4 is provided with a shutter unit (not shown) that opens and closes the entrance.

[0024] FIG. 2 is a schematic diagram for explaining the configuration of the wet processing unit 2W.

[0025] The wet processing unit 2W further includes a spin chuck 5 that rotates the substrate W about a rotation axis A1 while holding the substrate W at a predetermined holding position, a heating unit 6 that has a heating surface 6a facing the lower surface of the substrate W and heats the substrate W, and a plurality of processing liquid nozzles (etchant nozzle 8 and rinse liquid nozzle 9) that discharge processing liquid toward the upper surface (upper main surface) of the substrate W held on the spin chuck 5. The holding position is a position where the rotation axis A1 coincides with a central axis passing through the center of the upper surface of the substrate W, and where the upper surface of the substrate W is horizontal.

[0026] The spin chuck 5 and the plurality of processing liquid nozzles are disposed within a chamber 4 (see FIG. 1) together with a processing cup 7.

[0027] The spin chuck 5 is surrounded by a processing cup 7. The spin chuck 5 includes a spin base 20 that adsorbs to the lower surface of the substrate W and holds the substrate W at a predetermined holding position, a rotation shaft 21 that extends along a rotation axis A1 and is connected to the spin base 20, and a rotation drive mechanism 22 that rotates the rotation shaft 21 about the rotation axis A1.

[0028] The spin base 20 has an attraction surface 20a that attracts the substrate W to its lower surface. The attraction surface 20a is, for example, the upper surface of the spin base 20. The attraction surface 20a is, for example, a circular surface with the rotation axis A1 passing through its center. The diameter of the attraction surface 20a is smaller than the diameter of the substrate W.

[0029] A suction path 23 is inserted into the spin base 20 and the rotation shaft 21. The suction path 23 has a suction port 23a exposed from the center of the chucking surface 20a of the spin base 20. The suction path 23 is connected to a suction pipe 24. The suction pipe 24 is connected to a suction device 25 such as a vacuum pump. The suction device 25 may constitute a part of the substrate processing apparatus 1, or may be a device separate from the substrate processing apparatus 1 that is provided in a facility where the substrate processing apparatus 1 is installed.

[0030] The suction pipe 24 is provided with a suction valve 26 that opens and closes the suction pipe 24. By opening the suction valve 26, the substrate W placed on the suction surface 20a of the spin base 20 is sucked into the suction port 23a of the suction path 23. As a result, the substrate W is sucked onto the suction surface 20a from below and held at the holding position. The orientation of the substrate W held at the holding position is, for example, an orientation in which the upper surface of the substrate W is aligned horizontally. Furthermore, the substrate W may be centered by a centering unit (not shown) so that the central axis of the substrate W coincides with the rotation axis A1.

[0031] The rotation drive mechanism 22 includes an actuator such as an electric motor. The rotation shaft 21 is rotated by the rotation drive mechanism 22, thereby rotating the spin base 20. As a result, the substrate W is rotated together with the spin base 20 around the rotation axis A1.

[0032] The spin base 20 is an example of a substrate holding member that holds the substrate W at a predetermined holding position. The spin chuck 5 is an example of a rotation holding unit that rotates the substrate W around the rotation axis A1 while holding the substrate W at a predetermined holding position. The spin chuck 5 is also called an attraction rotation unit that rotates the substrate W while attracting the substrate W to the attraction surface 20a.

[0033] The multiple processing liquid nozzles include an etching liquid nozzle 8 that ejects a continuous flow of etching liquid toward the upper surface of the substrate W held on the spin chuck 5, and a rinsing liquid nozzle 9 that ejects a continuous flow of rinsing liquid toward the upper surface of the substrate W held on the spin chuck 5.

[0034] The etching liquid discharged from the etching liquid nozzle 8 contains an etching agent as a solute and a solvent that dissolves the etching agent. The etching agent is a substance that has the property of etching the processing target layer exposed from the main surface of the substrate W. The etching agent contains ammonium fluoride (NH4F).

[0035] The solvent may be any solvent capable of dissolving the etching agent, such as pure water (DIW). Therefore, an aqueous solution of ammonium fluoride can be used as the etching solution. The solvent is not limited to DIW, and can be selected from the liquids used as rinse solutions (described later).

[0036] The etching agent reacts with the target layer to form a solid layer containing a thermally decomposable solid. Ammonium fluoride, used as the etching agent, reacts with silicon oxide, the target layer, according to the following chemical reaction formulas 1 and 2.

[0037] Specifically, as shown in Chemical Reaction 1, ammonium fluoride reacts with silicon dioxide to form a solid layer containing primarily solid ammonium silicofluoride ((NH4)2SiF6). As shown in Chemical Reaction 2, ammonium silicofluoride decomposes upon heating. The decomposition of ammonium silicofluoride produces ammonia (NH3), hydrogen fluoride (HF), and silicon tetrafluoride (SiF4). All of these substances are gases at the reaction temperature.

[0038] [ka]

[0039] [ka]

[0040] Even if the layer to be treated contains silicon nitride, a solid layer containing solid-state ammonium silicofluoride is formed.

[0041] The mass percent concentration of the etching agent in the etching solution is preferably 0.2 wt% or more and less than 10 wt%, more preferably 0.2 wt% or more and 7.0 wt% or less, even more preferably 2.0 wt% or more and 7.0 wt% or less, and even more preferably 2.0 wt% or more and 6.0 wt% or less.

[0042] The rinse liquid discharged from the rinse liquid nozzle 9 is, for example, pure water such as DIW. However, the rinse liquid is not limited to DIW. The rinse liquid may be, for example, carbonated water, electrolytic ion water, diluted hydrochloric acid water (for example, 1 ppm or more and 100 ppm or less), diluted ammonia water (for example, 1 ppm or more and 100 ppm or less), or reduced water (hydrogen water).

[0043] In this embodiment, each processing liquid nozzle is a fixed nozzle whose position in the vertical and horizontal directions is fixed.

[0044] An etching liquid pipe 40 that guides the etching liquid to the etching liquid nozzle 8 is connected to the etching liquid nozzle 8. The etching liquid pipe 40 is provided with an etching liquid valve 50A that opens and closes the flow path in the etching liquid pipe 40, and an etching liquid flow rate adjustment valve 50B that adjusts the flow rate of the etching liquid in the etching liquid pipe 40. "A valve is provided in the pipe" may also mean that the valve is interposed in the pipe. When the etching liquid valve 50A is opened, the etching liquid is discharged from the etching liquid nozzle 8 at a flow rate that corresponds to the opening degree of the etching liquid flow rate adjustment valve 50B.

[0045] A rinse liquid pipe 41 that guides the rinse liquid to the rinse liquid nozzle 9 is connected to the rinse liquid nozzle 9. The rinse liquid pipe 41 is provided with a rinse liquid valve 51A that opens and closes a flow path in the rinse liquid pipe 41, and a rinse liquid flow rate adjustment valve 51B that adjusts the flow rate of the rinse liquid in the rinse liquid pipe 41. When the rinse liquid valve 51A is opened, the rinse liquid is discharged from the rinse liquid nozzle 9 at a flow rate that corresponds to the opening degree of the rinse liquid flow rate adjustment valve 51B.

[0046] The heating unit 6 is, for example, a hot plate that heats the substrate W. The heating unit 6 includes a plate body 60 that faces the substrate W from below, and a heater 61 built into the plate body 60. The heating unit 6 is, for example, formed in an annular shape that surrounds the spin base 20. The heating surface 6a is, for example, formed by the upper surface of the plate body 60. The heating surface 6a may be an annular surface that surrounds the spin base 20. The heater 61 may be a resistor built into the plate body 60. Power is supplied to the heater 61 from a power supply unit 63, such as a power source, via a power supply line 62. The set temperature of the heater 61 of the heating unit 6 is, for example, 50°C to 200°C.

[0047] The heating unit 6 is raised and lowered in the vertical direction by a heater lifting mechanism 64. The heater lifting mechanism 64 raises and lowers the heating unit 6 between a contact heating position (position shown by a solid line in FIG. 2) where the heating unit 6 heats the substrate W while in contact with the substrate W, and a non-heating position (position shown by a two-dot chain line in FIG. 2) where the heating unit 6 is spaced apart from the substrate W and is not heated. When positioned at the contact heating position, the heating unit 6 can heat the substrate W and the liquid on the substrate W to a temperature of 50°C or higher and 200°C or lower.

[0048] The heating unit 6 can also be disposed at a non-contact heating position where it heats the substrate W without coming into contact with the lower surface of the substrate W. The non-contact heating position is a position closer to the lower surface of the substrate W than the non-heating position.

[0049] The heater lifting mechanism 64 includes, for example, a ball screw mechanism (not shown) coupled to the plate body 60, and a motor (not shown) that provides a driving force to the ball screw mechanism. The heater lifting mechanism 64 is also called a heater lifter.

[0050] The processing cup 7 is a member that receives the processing liquid discharged from the substrate W. The processing cup 7 includes a cylindrical portion 70 that extends vertically, an inclined portion 71 that extends obliquely upward from the upper end of the cylindrical portion 70, and a substantially annular bottom portion 72 to which the processing liquid received by the inclined portion 71 and the cylindrical portion 70 is guided. A sealing member 73 such as a labyrinth seal is provided between the inner circumferential end of the bottom portion 72 and the rotation shaft 21. The sealing member 73 prevents leakage of the processing liquid from the bottom portion 72 of the processing cup 7.

[0051] A drain groove 74 is provided in the bottom 72, and the drain groove 74 is connected to a drain pipe 75. A drain valve 76 is provided in the drain pipe 75. When the drain valve 76 is opened, the processing liquid is discharged from the drain pipe 75 as waste liquid.

[0052] 3 is a block diagram for explaining the electrical configuration of the substrate processing apparatus 1. The controller 3 includes a microcomputer, and controls the controlled objects provided in the substrate processing apparatus 1 according to a predetermined control program.

[0053] Specifically, the controller 3 includes a processor 3A (CPU) and a memory 3B that stores a control program. The controller 3 is configured to perform various controls for substrate processing by the processor 3A executing the control program. In particular, the controller 3 is programmed to control the transfer robots IR and CR, the rotation drive mechanism 22, the heater lifting / lowering mechanism 64, the energization unit 63, the suction valve 26, the etching liquid valve 50A, the etching liquid flow rate adjustment valve 50B, the rinse liquid valve 51A, the rinse liquid flow rate adjustment valve 51B, the drain valve 76, and the like.

[0054] 3 shows representative members, but this does not mean that members not shown are not controlled by the controller 3, and the controller 3 can appropriately control each member provided in the substrate processing apparatus 1. FIG. 3 also shows members to be described in modified examples and the second embodiment, which will be described later, and these members are also controlled by the controller 3.

[0055] 4, which will be described later, is executed by the controller 3 controlling each member included in the substrate processing apparatus 1. In other words, the controller 3 is programmed to execute each step shown in FIG.

[0056] <Example of substrate processing> Fig. 4 is a flowchart for explaining the substrate processing performed by the substrate processing apparatus 1. Fig. 5 is a schematic diagram for explaining the state of the upper surface of the substrate W during the substrate processing.

[0057] In the substrate processing by the substrate processing apparatus 1, for example, an etching liquid supplying step (step S1), a liquid film forming step (step S2), a heating step (step S3), a rinsing liquid supplying step (step S4), and a drying step (step S5) are performed, as shown in Fig. 4. Details of the substrate processing will be described below mainly with reference to Fig. 2 and Fig. 4. Fig. 5 will also be referenced as appropriate.

[0058] First, an unprocessed substrate W is loaded from the carrier C into the processing unit 2 by the transport robot CR (see FIG. 1) and handed over to the spin chuck 5 (loading step). As a result, the substrate W is held in a holding position by the spin chuck 5 (substrate holding step). The substrate W is held by the spin chuck 5 so that the main surface on which the processing target layer is exposed faces upward. The spin chuck 5 starts to rotate the substrate W while holding it (rotation step). During substrate processing, the power supply unit 63 remains powered, and the heater 61 of the heating unit 6 is heated to a set temperature (for example, 50°C or higher and 200°C or lower).

[0059] After the substrate W is held by the spin chuck 5, an etching liquid supply step (step S1) is performed to supply an etching liquid to the upper surface of the substrate W. Specifically, the etching liquid valve 50A is opened. As a result, as shown in FIG. 5(a), the etching liquid is discharged from the etching liquid nozzle 8 and the etching liquid lands on the upper surface of the substrate W. The etching liquid that has landed on the upper surface of the substrate W spreads over the entire upper surface of the substrate W due to the action of centrifugal force.

[0060] The discharge flow rate of the etching liquid from the etching liquid nozzle 8 is, for example, 2000 mL / min. While the etching liquid is being supplied to the upper surface of the substrate W, the substrate W is rotated, for example, at 300 rpm or more and 700 rpm or less.

[0061] Next, a liquid film forming step (step S2) is performed to form a thin liquid film 150 of the etching liquid on the upper surface of the substrate W. Specifically, in the etching liquid supplying step, the etching liquid is discharged from the etching liquid nozzle 8 for a predetermined period (for example, a period of 5 seconds or more and 15 seconds or less), and then the etching liquid valve 50A is closed. This stops the discharge of the etching liquid from the etching liquid nozzle 8, and stops the supply of the etching liquid to the upper surface of the substrate W. Even after the supply of the etching liquid to the upper surface of the substrate W is stopped, the rotation of the substrate W continues (rotation continuing step, rotation step). Therefore, the etching liquid is removed from the upper surface of the substrate W, and a thin liquid film 150 (thin film) of the etching liquid is formed on the upper surface of the substrate W, as shown in FIG. 5(b) (liquid film forming step, thin film forming step). The rotation speed of the substrate W after the discharge of the etching liquid is stopped, i.e., the rotation speed of the substrate W in the liquid film forming step, is 2000 rpm or more and 4000 rpm or less.

[0062] After the supply of the etching liquid is stopped, a heating step (step S3) of heating the substrate W is started when a predetermined liquid film formation time (for example, 30 seconds or more and 140 seconds or less) has elapsed. Specifically, the rotation of the substrate W is stopped, and then the heater lifting mechanism 64 positions the heating unit 6 at the contact heating position. As a result, as shown in FIG. 5(c), a liquid film 150 on the upper surface of the substrate W is heated via the substrate W. The heating temperature of the liquid film 150 is, for example, the set temperature of the heating unit 6, and is 50°C or more and 200°C or less. Heating the liquid film 150 promotes the etching action of the etching agent in the etching liquid. As shown in FIG. 5(d), a solid layer 151 is formed on the upper surface of the substrate W by a reaction between the etching agent and the layer to be processed.

[0063] After the substrate W is heated for a predetermined heating time (for example, not less than 60 seconds and not more than 180 seconds), a rinse liquid supply step (step S4) is performed in which a rinse liquid is supplied to the upper surface of the substrate W. Specifically, the heater lifting mechanism 64 positions the heating unit 6 at the non-heating position. This stops heating of the substrate W. Thereafter, rotation of the substrate W is resumed, and the rinse liquid valve 51A is opened. As a result, as shown in FIG. 5(e), rinse liquid is discharged from the rinse liquid nozzle 9, and the rinse liquid lands on the upper surface of the rotating substrate W. The rinse liquid that has landed on the upper surface of the substrate W spreads over the entire upper surface of the substrate W due to the action of centrifugal force. As a result, the solid layer 151 on the upper surface of the substrate W is dissolved in the rinse liquid and discharged outside the substrate W.

[0064] The discharge flow rate of the rinse liquid from the rinse liquid nozzle 9 is, for example, 2000 mL / min. While the rinse liquid is being supplied to the upper surface of the substrate W, the substrate W is rotated, for example, at 1000 rpm or more and 2000 rpm or less.

[0065] Next, a drying step (step S5) is performed in which the substrate W is rotated at high speed to dry the upper surface of the substrate W. Specifically, the supply of the rinse liquid to the upper surface of the substrate W is stopped by closing the rinse liquid valve 51A.

[0066] Then, the rotation drive mechanism 22 accelerates the rotation of the substrate W, and the substrate W is rotated at high speed (for example, 1500 rpm). As a result, a large centrifugal force acts on the rinse liquid adhering to the substrate W, and the rinse liquid is thrown off around the substrate W.

[0067] After the drying step (step S5), the rotation drive mechanism 22 stops the rotation of the substrate W. Thereafter, the transport robot CR enters the processing unit 2, receives the processed substrate W from the spin chuck 5, and transports it out of the processing unit 2 (transport step). The substrate W is handed over from the transport robot CR to the transport robot IR, and is stored in the carrier C by the transport robot IR.

[0068] According to the first embodiment, the target layer includes at least one of a silicon oxide layer and a silicon nitride layer, and the etching solution contains ammonium fluoride as an etching agent. Therefore, heating can quickly cause the target layer to react with the etching agent present on the main surface of the substrate W, reducing the time dependency of etching of the target layer. In other words, saturated atomic layer etching can be achieved.

[0069] After the etching solution supplying step and before the heating step, the substrate W is rotated. This allows the amount of etching solution on the upper surface of the substrate W to be appropriately reduced, thereby controlling the total amount of etching agent present on the upper surface of the substrate W. Controlling the total amount of etching agent makes it easier to control the amount of etching of the layer to be processed. In particular, by rotating the substrate W at a rotational speed of 2000 rpm or more and 4000 rpm or less, the total amount of etching agent present on the upper surface of the substrate W can be accurately controlled.

[0070] If the mass percent concentration of the etching agent in the etching solution is 0.2 wt % or more and less than 10 wt %, saturated atomic layer etching is easily achieved.

[0071] If the heating temperature in the heating step is 50° C. or higher and 200° C. or lower, the layer to be treated and the etching agent present on the main surface of the substrate can react particularly quickly.

[0072] <An example of the mechanism of saturated atomic layer etching> Next, the mechanism of saturated atomic layer etching will be described. Fig. 6 is a schematic diagram for explaining an example of the mechanism when etching the processing target layer 100 exposed from the upper surface of the substrate W. In the liquid film formation step (step S2), a liquid film 150 is formed on the upper surface of the substrate W, as shown in Fig. 6(a).

[0073] A solid layer 151 is formed by a reaction between the etching agent in the etching solution on the upper surface of the substrate W and the layer to be processed 100. In the heating step (step S3), the liquid film 150 is heated through the substrate W, thereby promoting the formation of the solid layer 151, as shown in FIG. 6(b).

[0074] More specifically, etching progresses as the etching solution penetrates the solid layer 151 and reaches the layer to be treated 100. As the etching progresses, the thickness T of the solid layer 151 increases. Meanwhile, decomposition of the solid layer 151 progresses due to heating, and the reaction between the etching agent and the layer to be treated 100 is promoted (reaction promotion step).

[0075] More specifically, since the product of the decomposition of the solid layer 151 is gas, the gas diffuses into the atmosphere. This removes the product of the reaction between the etching solution and the layer 100 to be treated from the reaction system. As the product is removed, the decomposition of the solid layer 151 is promoted to increase the amount of product of the thermal decomposition reaction.

[0076] 6(c), etching of the layer to be processed 100 progresses until most of the etching agent on the upper surface of the substrate W is consumed, and then the etching is stopped. In this manner, at least a portion of the solid layer 151 formed by the reaction between the etching agent and the layer to be processed 100 is removed by heating, thereby accelerating the reaction between the etching agent and the layer to be processed 100.

[0077] The promotion of the reaction between the etching solution and the target layer 100 will be specifically explained using the above chemical reaction formulas 1 and 2. Ammonium silicofluoride ((NH4)2SiF6) is converted into various decomposition products (ammonia, hydrogen fluoride, and silicon tetrafluoride) through decomposition. Because the various decomposition products are in a gaseous state at the reaction temperature, they diffuse into the atmosphere. This removes the products of the reaction between the etching solution and the target layer 100 (the reaction shown in chemical reaction formula 1) from the reaction system. Therefore, the decomposition of ammonium silicofluoride is promoted to increase the amount of product of the thermal decomposition reaction, and the reaction shown in chemical reaction formula 2 proceeds to the right. Because the reaction shown in chemical reaction formula 2 proceeds to the right, the product of the reaction shown in chemical reaction formula 1 decreases, and chemical reaction formula 1 also proceeds to the right. In other words, the reaction between ammonium fluoride (NH4F) and silicon oxide (SiO2) is promoted. As a result, most of the ammonium fluoride is consumed.

[0078] Therefore, the etching depth D of the processing target layer 100 is proportional to the total amount of etching agent in the etching solution present on the upper surface of the substrate W at the start of the heating step. Therefore, by controlling the amount of etching solution present on the upper surface of the substrate W at the start of the heating step, the etching depth D can be controlled with high precision.

[0079] <Example of changes in the surface layer of the upper surface of a substrate due to substrate processing> Fig. 7A is a schematic diagram illustrating an example of the structure of the surface layer 110 on the upper surface of the substrate W processed by the substrate processing apparatus 1. Fig. 7B is a schematic diagram illustrating a change in the structure of the surface layer 110 on the upper surface of the substrate W shown in Fig. 7A due to etching.

[0080] As shown in Figure 7A, the surface layer 110 of the upper surface of the substrate W has a semiconductor layer 111, a stack 112 formed on the semiconductor layer 111, a plurality of channels 113 formed by digging into the surface of the stack 112, a plurality of processing target layers 100 buried respectively in the plurality of channels 113, and a covering layer 114 interposed between the channel 113 and the sidewall 113a of the channel 113 and covering the sidewall 113a of the channel 113.

[0081] The depth CD1 of the channel 113 is, for example, not less than 32 atomic layers and not more than 96 atomic layers. The channel 113 has, for example, a circular shape when viewed from the depth direction DD of the channel 113. The width L1 of the channel 113 (the diameter of the channel 113) is, for example, not less than 50 nm and not more than 90 nm.

[0082] The semiconductor layer 111 is made of, for example, single crystal Si. The stacked body 112 has a plurality of first insulating layers 115 and a plurality of second insulating layers 116. In the stacked body 112, the first insulating layers 115 and the second insulating layers 116 are alternately arranged along the depth direction DD of the channel 113. The first insulating layer 115 is, for example, a silicon oxide layer, and the second insulating layer 116 is, for example, a silicon nitride layer.

[0083] A fine uneven pattern is formed on the surface layer portion 110 by the sidewall 113a of the channel 113, the bottom wall 113b of the channel 113, and the tip surface 112a of the stacked body 112. The covering layer 114 covers the sidewall 113a of the channel 113 and the tip 112a of the stacked body 112. This prevents the stacked body 112 from being exposed to the etching solution. An example of a substrate W having a surface layer portion 110 with such a configuration is a substrate used in a manufacturing process for a three-dimensional NAND flash memory.

[0084] When the substrate W shown in Fig. 7A is subjected to the above-described substrate processing, a portion of the processing target layer 100 in the channel 113 is etched, as shown in Fig. 7B, and a desired etching depth D1 is achieved. Furthermore, because the processing target layer 100 can be etched by wet etching, it is possible to suppress damage to the fine concave-convex pattern and excessive etching of the processing target layer 100, which are problems when using dry etching techniques such as reactive ion etching. Damage to the fine concave-convex pattern means, for example, that the corners of the tip surface 112a of the stack 112 are scraped off, resulting in a rounded (curved) shape.

[0085] <Another example of changes in the surface layer of the upper surface of a substrate due to substrate processing> Fig. 8A is a schematic diagram illustrating another example of the structure of the surface layer 120 on the upper surface of the substrate W processed by the substrate processing apparatus 1. Fig. 8B is a schematic diagram illustrating a change in the structure of the surface layer 120 on the upper surface of the substrate W shown in Fig. 8A due to etching.

[0086] 8A, the surface layer portion 120 on the upper surface of the substrate W has a semiconductor layer 121, a plurality of structures 122 formed on the semiconductor layer 121, and a processing target layer 130 covering the plurality of structures 122. The processing target layer 130 has a first processing target layer 131 formed on each of the structures 122, and a second processing target layer 132 located between the plurality of structures 122.

[0087] The semiconductor layer 121 and the plurality of structures 122 are made of, for example, single crystal Si. The first processing target layer 131 has, for example, a first layer 133 made of a silicon oxide layer and a second layer 134 made of a silicon nitride layer formed on the first layer 133. The first processing target layer 131 is, for example, a silicon oxide layer, and is located between adjacent structures 122 so as to be in contact with the first processing target layer 131 and the structures 122.

[0088] The structures 122 are linear (strip-shaped) when viewed in the height direction TD of the structures 122, and the multiple structures 122 are arranged at intervals. The width L2 of the structures 122 is the width in the short direction of the structures 122 (the arrangement direction of the structures 122) when viewed in the height direction TD of the structures 122, and is, for example, not less than 5 nm and not more than 22 nm. The width L3 of the gap between the structures 122 is, for example, not less than 24 nm and not more than 60 nm.

[0089] A fine concave-convex pattern is formed on the surface layer 120 by the plurality of structures 122. An example of a substrate W having a surface layer 120 with such a configuration is a substrate used in a CMOS manufacturing process.

[0090] When such a substrate W is subjected to the above-described substrate processing, a portion of the processing target layer 130 is etched, achieving a desired etching depth D2, as shown in FIG. 8B . Specifically, the entire first processing target layer 131 is removed by etching. Then, a portion of the second processing target layer 132 is removed by etching so that its surface is located closer to the semiconductor layer 121 than the tip portions 122a of the multiple structures 122. The etched processing target layer 130 functions as an interlayer insulating film. Because the processing target layer 130 can be etched by wet etching, damage to the fine uneven pattern and excessive etching of the processing target layer 130 can be suppressed. When the desired etching depth D2 is achieved, the structures 122 have protruding portions 122b protruding from the second processing target layer 132. The height T2 of the protruding portions 122b is, for example, 34 nm or more and 60 nm or less.

[0091] <Modification of Wet Processing Unit> Figure 9 is a schematic diagram illustrating a modified example of a wet processing unit 2W. As shown in Figure 9, the wet processing unit 2W may include, instead of the heating unit 6 (see Figure 2), a heated gas nozzle 10 that supplies heated gas toward the upper surface of the substrate W to heat the substrate W and the liquid film 150 on the substrate W. The wet processing unit 2W shown in Figure 9 includes a facing member 11 having a facing surface 11a facing the upper surface of the substrate W, and a facing member lifting mechanism 12 that lifts and lowers the facing member 11.

[0092] The heated gas nozzle 10 has an outlet 10a exposed from the opposing surface 11a. The heated gas discharged from the heated gas nozzle 10 is, for example, an inert gas such as nitrogen gas, air, or a mixture of these. The inert gas is not limited to nitrogen gas, and may contain a rare gas such as argon gas. The temperature of the heated gas is, for example, 50°C or higher and 200°C or lower.

[0093] A heated gas pipe 42 that guides heated gas to the heated gas nozzle 10 is connected to the heated gas nozzle 10. The heated gas pipe 42 is provided with a heated gas valve 52A that opens and closes the flow path in the heated gas pipe 42, and a heated gas flow rate adjustment valve 52B that adjusts the flow rate of the heated gas in the heated gas pipe 42. When the heated gas valve 52A is opened, heated gas is discharged from the heated gas nozzle 10 at a flow rate that corresponds to the opening degree of the heated gas flow rate adjustment valve 52B.

[0094] The facing member 11 includes a circular facing portion 80 facing the upper surface of the substrate W, and an annular portion 81 extending downward from the peripheral edge of the facing portion 80. The facing surface 11a is, for example, the lower surface of the facing portion 80. The facing member 11 can be moved by the facing member lifting mechanism 12 between a proximity position (position shown by a two-dot chain line in FIG. 9) in which it is close to the upper surface of the substrate W, and a distant position (position shown by a solid line in FIG. 9) that is higher than the proximity position. When the facing member 11 is located in the proximity position, the annular portion 81 faces the substrate W in the horizontal direction.

[0095] The opposing member lifting mechanism 12 includes, for example, a ball screw mechanism (not shown) coupled to the opposing member 11, and a motor (not shown) that provides a driving force to the ball screw mechanism. The opposing member lifting mechanism 12 is also called an opposing member lifter.

[0096] When the facing member 11 is located at the close position, a processing space SP is formed by the facing portion 80, the annular portion 81, and the substrate W. When the processing space SP is formed, the heated gas valve 52A is opened, so that the gas in the processing space SP can be quickly replaced with heated gas. This allows the substrate W and the liquid film 150 to be quickly heated.

[0097] <Configuration of Substrate Processing Apparatus According to Second Embodiment> 10 is a schematic plan view showing the layout of a substrate processing apparatus 1A according to the second embodiment. The substrate processing apparatus 1A includes a plurality of processing units 2 including a plurality of dry processing units 2D in addition to a plurality of wet processing units 2W.

[0098] 10, the two processing towers TW on the transfer robot IR side are made up of multiple wet processing units 2W, and the two processing towers TW on the opposite side of the transfer robot IR are made up of multiple dry processing units 2D. The dry processing units 2D are disposed within the chamber 4 and include heat treatment chambers 90 for heating the substrates W therein.

[0099] 11 is a schematic diagram illustrating the configuration of a wet processing unit 2W according to the second embodiment. As shown in FIG. 11, the wet processing unit 2W according to the second embodiment is not provided with a configuration for heating the substrate W, unlike the first embodiment.

[0100] FIG. 12 is a schematic diagram for explaining the configuration of the dry processing unit 2D.

[0101] The dry processing unit 2D is accommodated in the heat treatment chamber 90 and further includes a heating unit 91 having a heating surface 91a on which the substrate W is placed. The heating unit 91 has the form of a disk-shaped hot plate. The heating unit 91 includes a plate body 92 and a heater 93. The upper surface of the plate body 92 forms the heating surface 91a. The heater 93 may be a resistor built into the plate body 92. The heater 93 can heat the substrate W to a temperature approximately equal to the temperature of the heater 93. The heater 93 is heated to a set temperature (for example, 50°C or higher and 200°C or lower). Specifically, a current supply unit 94 such as a power supply is connected to the heater 93, and the temperature of the heater 93 changes to a temperature within a predetermined temperature range by adjusting the current supplied from the current supply unit 94.

[0102] The heat treatment chamber 90 includes a chamber body 90A that opens upward, and a lid 90B that moves up and down above the chamber body 90A to close the opening of the chamber body 90A. When the opening of the chamber body 90A is open (as shown by the two-dot chain line in FIG. 12), the transfer robot CR can access the inside of the heat treatment chamber 90.

[0103] The dry processing unit 2D further includes a plurality of lift pins 96 that move up and down while penetrating the plate body 92. The plurality of lift pins 96 are movable up and down between an upper position (position indicated by a two-dot chain line in FIG. 12) where they support the substrate W above the heating surface 91a, and a lower position (position indicated by a solid line in FIG. 12) where their tips (upper ends) are recessed below the heating surface 91a.

[0104] The substrate processing apparatus 1A according to the second embodiment can perform substrate processing similar to that of the first embodiment (see FIGS. 4 and 5). However, before and after the heating step (step S4), the substrate W is transported between the wet processing unit 2W and the dry processing unit 2D. In the heating step (step S4), the liquid film 150 is heated by the heating unit 91 via the substrate W while the lift pins 96 are positioned in the lower position and the opening of the chamber body 90A is closed by the lid 90B (the state shown by the solid line in FIG. 12).

[0105] <Experiment to demonstrate saturated atomic layer etching> Next, the results of the experiments conducted to demonstrate saturated atomic layer etching will be described.

[0106] [Time change experiment] First, a time-varying experiment conducted to observe the time dependency of etching will be described. Fig. 13A is a schematic diagram illustrating the procedure of the time-varying experiment to observe the time dependency of etching. The time-varying experiment was conducted by the following steps (a) to (d).

[0107] (a) A 2.5 cm square substrate piece (hereinafter referred to as "substrate piece 200") on which a 100 nm thick silicon oxide film was formed was placed on a heater 201, and 1 mL of an ammonium fluoride aqueous solution (etchant) was supplied to the main surface of the substrate piece 200. The mass percent concentration of ammonium fluoride (etchant) in the ammonium fluoride aqueous solution was 2 wt%.

[0108] (b) Thereafter, the small substrate piece 200 was rotated by rotating the heater 201 for a predetermined rotation time. By rotating the small substrate piece 200, the ammonium fluoride aqueous solution on the small substrate piece 200 spreads over the entire main surface of the small substrate piece 200, and a thin film 202 of the ammonium fluoride aqueous solution is formed on the main surface of the small substrate piece 200. At this time, the rotation of the small substrate piece 200 was started at 500 rpm, and the rotation speed of the small substrate piece 200 was gradually accelerated so that the rotation speed of the small substrate piece 200 reached 3000 rpm 20 seconds after the start of rotation. Five types of small substrate piece 200 were prepared with rotation times of 30 seconds, 40 seconds, 60 seconds, 80 seconds, and 140 seconds, respectively.

[0109] (c) After that, the five types of small substrate 200 rotated for each rotation time were heated by the heater 201. The heating was performed at 200° C. for 180 seconds.

[0110] (d) After that, each small substrate 200 was rinsed with a rinse liquid.

[0111] Using this procedure, five types of heated substrate pieces 200 were prepared as "heated samples." On the other hand, a substrate piece 200 that was subjected to procedures (a), (b), and (d) without performing procedure (c) was prepared as an "unheated sample." The amount of silicon oxide film removed (etched amount) of these samples was then measured using an SEM or the like.

[0112] FIG. 13B is a graph showing the results of a time-varying experiment, illustrating the relationship between the rotation time of the substrate piece 200 and the etching amount. As shown in FIG. 13B, when a heated sample was used, the etching amount was similar at all rotation times, approximately 4.0 nm to 4.2 nm. On the other hand, for the unheated sample, the etching amount increased over time, gradually approaching 4.0 nm. This suggests that heating promotes etching. When the etching solution was heated via the substrate piece 200, etching was completed at least by the time the rotation time reached 30 seconds, demonstrating that the etching amount had very little dependency on the rotation time.

[0113] [Concentration change experiment] Next, a concentration change experiment conducted to observe the concentration dependency of etching will be described. In the concentration change experiment, the following steps (a) to (d) were performed. The procedure for the concentration change experiment is generally the same as the procedure for the time change experiment described above, so the procedure will be described with reference to FIG. 13A.

[0114] (a) A small substrate piece 200 was placed on a heater 201, and 1 ml of an ammonium fluoride aqueous solution was supplied to the main surface of the small substrate piece 200. Five types of small substrate piece 200 were prepared, each with an ammonium fluoride concentration of 2 wt%, 4 wt%, 6 wt%, and 10 wt%, respectively, in the ammonium fluoride aqueous solution supplied to the small substrate piece 200.

[0115] (b) Thereafter, the small substrate piece 200 was rotated by rotating the heater 201 for a predetermined rotation time. By rotating the small substrate piece 200, the ammonium fluoride aqueous solution on the small substrate piece 200 spreads over the entire main surface of the small substrate piece 200, and a thin film 202 of ammonium fluoride is formed on the main surface of the small substrate piece 200. At this time, the rotation of the small substrate piece 200 was started at 500 rpm, and the rotation of the small substrate piece 200 was gradually accelerated so that the rotation speed of the small substrate piece 200 reached 3000 rpm 20 seconds after the start of rotation, and the small substrate piece 200 was rotated until 80 seconds had elapsed from the start of rotation.

[0116] (c) After that, each small substrate 200 was heated by the heater 201. Heating was performed at 200° C. for 180 seconds.

[0117] (d) After that, each small substrate 200 was rinsed with a rinse liquid.

[0118] Using this procedure, five types of small substrate pieces 200 with different supply amounts of etching agent were prepared. The removal amounts (etching amounts) of the silicon oxide film of these five types of small substrate pieces 200 were measured using an SEM or the like.

[0119] FIG. 14 is a graph showing the results of the concentration change experiment. As shown in FIG. 14, when the ammonium fluoride concentration was 2 wt%, the etching amount was approximately 4.1 nm, and when the ammonium fluoride concentration was 4 wt%, the etching amount was approximately 6.1 nm. When the ammonium fluoride concentration was 6 wt%, the etching amount was approximately 7.5 nm, and when the ammonium fluoride concentration was 10 wt%, the etching amount was approximately 12.5 nm. Thus, the etching amount increased as the ammonium fluoride concentration increased. This shows that the etching amount varies depending on the concentration of the etching agent. The difference in the etching amount within the concentration range of 2 wt% to 10 wt% was 8.4 nm.

[0120] [Crystal observation experiment] Next, a crystal observation experiment for observing the generation of crystals in the etching solution will be described. In the crystal observation experiment, the following steps (a) to (d) were performed for multiple concentrations. The procedure for the crystal observation experiment is generally the same as the procedure for the time change experiment described above, so it will be described with reference to FIG. 13A.

[0121] (a) A small substrate piece 200 was placed on a heater 201, and 1 mL of an aqueous ammonium solution was supplied to the main surface of the small substrate piece 200. Five types of small substrate piece 200 were prepared, each with an ammonium fluoride concentration of 2 wt%, 4 wt%, 6 wt%, 10 wt%, and 15 wt% in the aqueous ammonium fluoride solution supplied to the small substrate piece 200.

[0122] (b) Thereafter, the heater 201 was rotated to rotate the small substrate piece 200 for a predetermined rotation time. At this time, the rotation of the small substrate piece 200 was started at 500 rpm, and the rotation of the small substrate piece 200 was gradually accelerated so that the rotation speed of the small substrate piece 200 reached 3000 rpm 20 seconds after the start of rotation. Five types of small substrate piece 200 were prepared, each with a rotation time of 30 seconds, 40 seconds, 50 seconds, 60 seconds, and 80 seconds for the small substrate piece 200 to which aqueous ammonium fluoride solutions of various concentrations had been supplied.

[0123] (c) After that, each small substrate 200 was heated by the heater 201. Heating was performed at 200° C. for 180 seconds.

[0124] (d) After that, each small substrate 200 was rinsed with a rinse liquid.

[0125] Using this procedure, we prepared a plurality of types (25 types in total) of small substrate pieces 200 with different rotation times and etching agent supply amounts. The states of the main surfaces of these plurality of types of small substrate pieces 200 were measured using an SEM or the like.

[0126] FIG. 15 is a table showing the results of a crystal observation experiment. As shown in FIG. 15, when the mass percent concentration of ammonium fluoride in the ammonium fluoride aqueous solution was 2 wt%, 4 wt%, or 6 wt%, no crystal formation was observed regardless of the rotation time of the small substrate piece 200. On the other hand, when the mass percent concentration of ammonium fluoride in the ammonium fluoride aqueous solution was 10 wt%, crystal formation was observed when the rotation time was longer than 30 seconds. Furthermore, when the mass percent concentration of ammonium fluoride in the ammonium fluoride aqueous solution was 15 wt%, crystal formation was observed regardless of the rotation time. The formation of crystals may reduce the etching uniformity on the main surface of the small substrate piece 200.

[0127] Based on the results of the concentration change experiment shown in FIG. 14 and the crystal observation experiment shown in FIG. 15, the following can be inferred. When the mass percent concentration of ammonium fluoride in the etching solution is less than 10 wt%, the silicon oxide film can be sufficiently etched while maintaining good in-plane etching uniformity. In particular, when the mass percent concentration of ammonium fluoride in the etching solution is 2 wt% or more and less than 10 wt%, such an effect is easily achieved. When the mass percent concentration of ammonium fluoride in the etching solution is 2 wt% or more and 6 wt% or less, such an effect is even more easily achieved.

[0128] [Rotation speed change experiment] Next, a rotation speed change experiment for observing the rotation speed dependency of etching will be described. The rotation speed change experiment was carried out according to the following steps (a) to (d). The procedure for the rotation speed change experiment is generally the same as the procedure for the time change experiment described above, so it will be described with reference to FIG. 13A.

[0129] (a) The substrate piece 200 was placed on the heater 201, and 1 mL of an aqueous solution of ammonium fluoride, the mass percent concentration of which was 2 wt %, was supplied to the main surface of the substrate piece 200.

[0130] (b) Then, the heater 201 was rotated for a predetermined rotation time to rotate the small substrate 200. By rotating the small substrate 200, the ammonium fluoride aqueous solution on the small substrate 200 spreads over the entire main surface of the small substrate 200, forming a thin film 202 of ammonium fluoride on the main surface of the small substrate 200. At this time, the small substrate 200 started to rotate at 500 rpm, and the rotation of the small substrate 200 was accelerated so that the rotation speed of the small substrate 200 reached a predetermined thinning speed about 5 seconds after the start of rotation. The small substrate 200 continued to rotate at the thinning speed until about 80 seconds had elapsed after the start of rotation. Five types of small substrate 200 were prepared, each with a thinning speed of 2000 rpm, 2500 rpm, 3000 rpm, 3500 rpm, and 4000 rpm.

[0131] (c) After that, the five types of small substrate 200 rotated for each rotation time were heated by the heater 201. The heating was performed at 180° C. for 180 seconds.

[0132] (d) After that, each small substrate 200 was rinsed with a rinse liquid.

[0133] Five types of small substrate pieces with different thinning rates were prepared using this procedure. The removal amount (etching amount) of the silicon oxide film of these five types of small substrate pieces 200 was measured using an SEM or the like.

[0134] Fig. 16 is a graph showing the results of the experiment on changing the rotation speed. As shown in Fig. 16, when the thinning speed was in the range of 2000 rpm or more and 3000 rpm or less, the etching amount tended to decrease as the thinning speed increased. Specifically, when the thinning speed was 2000 rpm, the etching amount was approximately 5.6 nm, when the thinning speed was 2500 rpm, the etching amount was approximately 4.8 nm, and when the thinning speed was 3000 rpm, the etching amount was approximately 4.1 nm. Thus, it was shown that the etching amount changed depending on the thinning speed.

[0135] When the thinning speed was in the range of 3000 rpm or more and 4000 rpm or less, the etching amount was roughly constant regardless of the thinning speed. The reason for this is thought to be that when the thinning speed was 3000 rpm, the ammonium fluoride aqueous solution on the small substrate piece 200 was thinned to its limit, and even if the rotation speed was increased, no change occurred in the amount of ammonium fluoride aqueous solution on the small substrate piece 200, so no change occurred in the etching amount within the above rotation speed range.

[0136] The change in etching amount due to the change in the thinning speed was approximately 1.7 nm, whereas in the concentration change experiment (see Figure 14), the change in etching amount due to the change in the ammonium fluoride concentration was a maximum of approximately 8.4 nm. Therefore, it is inferred that the etching amount can be precisely controlled by adjusting the thinning speed, i.e., by controlling the rotation speed of the substrate.

[0137] [Temperature change experiment] Next, a temperature change experiment for observing the heating temperature dependency of etching will be described. The temperature change experiment was carried out according to the following steps (a) to (d). The procedure for the temperature change experiment is generally the same as the procedure for the time change experiment described above, so it will be described with reference to FIG. 13A.

[0138] (a) The substrate piece 200 was placed on the heater 201, and 1 mL of an aqueous solution of ammonium fluoride, the mass percent concentration of which was 2 wt %, was supplied to the main surface of the substrate piece 200.

[0139] (b) Thereafter, the small substrate 200 was rotated by rotating the heater 201 for a predetermined rotation time. By rotating the small substrate 200, the ammonium fluoride aqueous solution on the small substrate 200 spreads over the entire main surface of the small substrate 200, and a thin film of ammonium fluoride is formed on the main surface of the small substrate 200. At this time, the rotation of the small substrate 200 was started at 500 rpm, and the rotation of the small substrate 200 was gradually accelerated so that the rotation speed of the small substrate 200 reached 3000 rpm 20 seconds after the start of rotation, and the small substrate 200 was rotated until 80 seconds had elapsed from the start of rotation.

[0140] (c) Thereafter, the substrate piece 200 was heated by the heater 201. Four types of substrate piece 200 were prepared, each heated at a temperature of 50° C., 80° C., 150° C., and 180° C.

[0141] (d) After that, each small substrate 200 was rinsed with a rinse liquid.

[0142] Using this procedure, four types of small substrate pieces 200 with different heating temperatures were prepared. The removal amount (etching amount) of the silicon oxide film of these four types of small substrate pieces 200 was measured using an SEM or the like.

[0143] Figure 17 is a graph showing the results of the temperature change experiment. As shown in Figure 17, the etching amount was about 4.5 nm regardless of the heating temperature. Therefore, it was shown that sufficient etching was possible regardless of the heating temperature as long as the temperature was at least in the range of 50°C or higher and 180°C or lower.

[0144] <Other embodiments> The present invention is not limited to the above-described embodiment, and can be embodied in other forms.

[0145] (1) For example, in each of the above-described embodiments, the substrate processing is performed on the upper surface of the substrate W. However, the substrate processing may also be performed on the lower surface of the substrate W.

[0146] (2) In each of the above-described embodiments, the spin chuck 5 is a vacuum suction-type spin chuck that suctions the substrate W to the spin base 20. However, the spin chuck 5 may be a gripping-type spin chuck that grips the periphery of the substrate W with multiple chuck pins.

[0147] (3) The spin chuck 5 does not necessarily need to hold the substrate W horizontally. That is, unlike in FIG. 3, the spin chuck 5 may hold the substrate W vertically, or may hold the substrate W so that the top surface of the substrate W is inclined relative to the horizontal plane.

[0148] (4) In the above-described embodiments, the solid formed by the reaction between the etching agent in the etching solution and the target layer is decomposed by heating, thereby accelerating the reaction between the etching agent and the target layer. However, the reaction between the etching agent and the target layer may also be accelerated by the substance formed by the reaction between the etching agent and the target layer changing state to gas (mainly by sublimation) without being decomposed.

[0149] (5) Unlike the above-described embodiment, the rotation of the substrate W may be stopped during the etching liquid supplying step.

[0150] (6) In each of the above-described embodiments, a plurality of fluids are ejected from a plurality of nozzles, respectively. However, the manner in which each fluid is ejected is not limited to the above-described embodiments.

[0151] For example, each processing liquid nozzle may be a movable nozzle that is horizontally movable. Alternatively, all processing liquid nozzles may be configured to be moved together by a single nozzle moving mechanism. Alternatively, all fluids may be ejected from a single nozzle toward the top surface of the substrate W.

[0152] (7) In each of the above-described embodiments, although illustrations of pipes, pumps, valves, actuators, etc. are omitted, this does not mean that these components do not exist, and in reality, these components are provided in appropriate positions. For example, each pipe may be provided with a flow rate adjustment valve (not shown) that adjusts the flow rate of the processing liquid discharged from the corresponding processing liquid nozzle.

[0153] (8) In each of the above-described embodiments, the controller 3 controls the entire substrate processing apparatus 1. However, the controllers controlling the components of the substrate processing apparatus 1 may be distributed across multiple locations. Furthermore, the controller 3 does not need to directly control each component, and signals output from the controller 3 may be received by a slave controller that controls each component of the substrate processing apparatus 1.

[0154] (9) In the above-described embodiment, the substrate processing apparatus 1 includes the transport robots IR and CR, the plurality of processing units 2, and the controller 3. However, the substrate processing apparatus 1 may include a single processing unit 2 and the controller 3, and may not include a transport robot. Alternatively, the substrate processing apparatus 1 may include only a single processing unit 2. In other words, the processing unit 2 may be an example of the substrate processing apparatus.

[0155] In addition, various modifications can be made within the scope of the claims. [Explanation of symbols]

[0156] 100: Processing target layer 112: Laminate (insulating layer) 113: Channel 114: Covering layer 121: Semiconductor layer 122 :Structure 130: Processing target layer 151 :Solid layer A1: Rotation axis (center axis) D: Etching depth (etching amount) D1: Etching depth (etching amount) D2: Etching depth (etching amount) W: Substrate

Claims

1. 1. A substrate processing method for processing a substrate having a main surface on which at least one of a silicon oxide layer and a silicon nitride layer is exposed as a processing target layer, comprising: an etching solution supplying step of supplying an etching solution containing ammonium fluoride as an etching agent for etching the processing target layer onto the main surface of the substrate; a liquid film forming step of stopping the supply of the etching liquid and removing a portion of the etching liquid to form a liquid film of the etching liquid; a heating step of heating the etching liquid on the main surface of the substrate after the liquid film forming step; a rinsing liquid supplying step of supplying a rinsing liquid to the main surface of the substrate after the heating step.

2. A substrate processing method as described in claim 1, wherein the ammonium fluoride contained in the etching solution reacts with the main surface of the substrate to form a solid layer on the main surface of the substrate.

3. A substrate processing method as described in claim 2, wherein the solid layer contains ammonium silicofluoride.

4. A substrate processing method as described in claim 3, wherein, in the heating process, the ammonium silicofluoride contained in the solid layer is converted into a gaseous decomposition product.

5. A substrate processing method described in any one of claims 1 to 4, further comprising a rotation process in the liquid film formation process of rotating the substrate around a central axis passing through the center of the main surface of the substrate.

6. 6. The substrate processing method according to claim 5, wherein the rotating step includes the step of rotating the substrate at a rotational speed of not less than 2000 rpm and not more than 4000 rpm.

7. 7. The substrate processing method according to claim 1, wherein a mass percent concentration of the etching agent in the etching liquid supplied to the main surface of the substrate is equal to or greater than 0.2 wt % and less than 10 wt %.

8. 8. The substrate processing method according to claim 1, wherein the substrate is heated to a temperature of 50° C. or higher and 200° C. or lower in the heating step.

9. 9. The substrate processing method according to claim 1, wherein the etching depth of the layer to be processed is proportional to the total amount of the etching agent in the etching solution present on the main surface of the substrate at the start of the heating step.

10. 10. The substrate processing method according to claim 1, wherein the heating step includes a reaction promotion step of promoting a reaction between the etching agent in the etching solution on the main surface of the substrate and the processing target layer by removing, by heating, a solid layer formed on the processing target layer by a reaction between the etching agent and the processing target layer.

11. The substrate processing method according to any one of claims 1 to 10, wherein the substrate further comprises an insulating layer, a channel formed by digging into the surface of the insulating layer and in which the layer to be processed is buried, and a covering layer interposed between the layer to be processed and a sidewall of the channel and covering the sidewall of the channel.

12. The substrate processing method according to any one of claims 1 to 10, wherein the substrate further has a semiconductor layer and a plurality of structures formed on the semiconductor layer, the plurality of structures being covered by the processing target layer.

13. A substrate processing method for processing a substrate having a main surface on which at least one of a silicon oxide layer and a silicon nitride layer is exposed as a processing target layer, comprising: an etching solution supplying step of supplying an etching solution containing ammonium fluoride as an etching agent for etching the processing target layer onto the main surface of the substrate; a rotation step of rotating the substrate around a central axis passing through a center of the main surface of the substrate at a rotation speed of 2000 rpm or more and 4000 rpm or less after stopping the supply of the etching solution to the main surface of the substrate in the etching solution supply step; a heating step of heating the etching solution on the main surface of the substrate after the rotating step; a rinsing liquid supplying step of supplying a rinsing liquid to the main surface of the substrate after the heating step.

Images