SUBSTRATE PROCESSING METHOD AND SUBSTRATE PROCESSING APPARATUS

Abstract

To provide a substrate-processing method and a substrate-processing device which allow, by using phosphoric acid, a silicon oxide and a silicon nitride to be etched at etching rates equal or almost equal to each other.SOLUTION: In a substrate-processing method and a substrate-processing device, fluoride-containing phosphoric acid is kept at a given etching temperature which is coincident with or brought close to an isokinetic temperature where an etching rate of a silicon oxide film O1 and an etching rate of a silicon nitride film N1 are identical to each other at concentration of fluoride in the fluoride-containing phosphoric acid by heating the fluoride-containing phosphoric acid which is phosphoric acid containing fluoride. In the method and the device according to the present invention, the silicon oxide film O1 and the silicon nitride film N1 are etched by the fluoride-containing phosphoric acid in such a manner that the fluoride-containing phosphoric acid of the etching temperature is brought into contact with a silicon oxide film O1 and a silicon nitride film N1, formed on a substrate W.SELECTED DRAWING: Figure 3

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] Patent Document 1 discloses that, in manufacturing a three-dimensional NAND device, phosphoric acid is supplied to silicon oxide and silicon nitride to etch the silicon oxide and silicon nitride with a selectivity of greater than 100:1 (silicon nitride is 100).

[0003] Patent Document 2 discloses supplying an aqueous phosphoric acid solution to the surface of a silicon wafer on which a silicon oxide film and a silicon nitride film are exposed, and etching the silicon nitride film while suppressing etching of the silicon oxide film. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2021-530874 [Patent Document 2] JP 2018-182228 A Summary of the Invention [Problem to be solved by the invention]

[0005] When supplying phosphoric acid to a substrate such as a semiconductor wafer to etch silicon oxide and silicon nitride, it is usually required to etch silicon nitride at a high selectivity ratio as described in Patent Documents 1 and 2. However, there are cases where it is required to etch silicon oxide and silicon nitride at equal or nearly equal etching rates using phosphoric acid. Patent Documents 1 and 2 cannot meet such requirements.

[0006] SUMMARY OF THE PRESENTLY PREFERRED EMBODIMENTS Accordingly, one object of the present invention is to provide a substrate processing method and substrate processing apparatus capable of etching silicon oxide and silicon nitride at equal or nearly equal etching rates using phosphoric acid. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, one embodiment of the present invention provides a substrate processing method including: a phosphoric acid heating step of heating fluoride-containing phosphoric acid, which is phosphoric acid containing fluoride, to maintain the fluoride-containing phosphoric acid at an etching temperature that coincides with or approaches an isokinetic temperature at which the etching rates of a silicon oxide film and a silicon nitride film are equal at the fluoride concentration in the fluoride-containing phosphoric acid; and a phosphoric acid supplying step of contacting the fluoride-containing phosphoric acid at the etching temperature with the silicon oxide film and silicon nitride film formed on a substrate, thereby etching the silicon oxide film and the silicon nitride film with the fluoride-containing phosphoric acid.

[0008] According to this method, the silicon oxide film and silicon nitride film formed on the substrate are etched with fluoride-containing phosphoric acid, which is phosphoric acid containing fluoride, by contacting the silicon oxide film and silicon nitride film formed on the substrate with fluoride-containing phosphoric acid. The fluoride-containing phosphoric acid is maintained at an etching temperature that is equal to or close to the isokinetic temperature at which the etching rates of the silicon oxide film and the silicon nitride film are equal to each other at the fluoride concentration in the fluoride-containing phosphoric acid. Therefore, the silicon oxide film and the silicon nitride film can be etched at equal or nearly equal etching rates.

[0009] The isokinetic temperature depends on the concentration of fluoride in the fluoride-containing phosphoric acid. In a typical substrate processing, the concentration of fluoride in the fluoride-containing phosphoric acid is kept nearly constant, and therefore the isokinetic temperature is nearly constant. Accordingly, the fluoride-containing phosphoric acid is maintained at a constant etching temperature.

[0010] A silicon oxide film is a thin film of silicon oxide. Silicon oxide may be a compound whose chemical formula contains only Si (silicon) and O (oxygen), or may be a compound whose chemical formula contains elements other than Si and O. A typical example of silicon oxide is SiO 2 It is.

[0011] A silicon nitride film is a thin film of silicon nitride. Silicon nitride may be a compound whose chemical formula contains only Si (silicon) and N (nitrogen), or may contain elements other than Si and N. Typical examples of silicon nitride are SiN or Si 3 N 4 The number of Si in the chemical formula of silicon nitride may be other than 1 or 3. The number of N in the chemical formula of silicon nitride may be other than 1 or 4.

[0012] The etching rate of a silicon oxide film represents the amount of reduction in the thickness of the silicon oxide film per unit time. The same applies to the etching rate of a silicon nitride film. The selectivity of a silicon nitride film to a silicon oxide film represents the ratio of the etching rate of a silicon nitride film to the etching rate of a silicon oxide film (selectivity of a silicon nitride film to a silicon oxide film = etching rate of a silicon nitride film / etching rate of a silicon oxide film). Hereinafter, the selectivity of a silicon nitride film to a silicon oxide film may be simply referred to as the selectivity.

[0013] In the embodiment, at least one of the following features may be added to the substrate processing method.

[0014] The fluoride is a compound that increases the etching rate of the silicon oxide film and the etching rate of the silicon nitride film, and is preferably a compound that increases the etching rate of the silicon oxide film and the etching rate of the silicon nitride film as the concentration of the fluoride in the fluoride-containing phosphoric acid increases.

[0015] According to this method, a fluoride-containing phosphoric acid containing fluoride at an etching temperature that increases the etching rate of a silicon oxide film and an etching rate of a silicon nitride film is contacted with a silicon oxide film and a silicon nitride film formed on a substrate. This allows the silicon oxide film to be etched at a higher etching rate than when the silicon oxide film is etched with phosphoric acid that does not contain fluoride, and allows the silicon nitride film to be etched at a higher etching rate than when the silicon nitride film is etched with phosphoric acid that does not contain fluoride. As a result, the processing time of the substrate can be shortened, and the consumption of energy such as electricity can be reduced.

[0016] When the concentration of the fluoride in the fluoride-containing phosphoric acid is constant, the etching rate of the silicon oxide film is greater than the etching rate of the silicon nitride film at temperatures lower than the constant rate temperature, and the etching rate of the silicon oxide film is smaller than the etching rate of the silicon nitride film at temperatures higher than the constant rate temperature.

[0017] According to this method, fluoride-containing phosphoric acid, whose selectivity changes with temperature, is maintained at or near a constant temperature, and the fluoride-containing phosphoric acid at this temperature is brought into contact with the silicon oxide film and silicon nitride film formed on the substrate. When the concentration of fluoride in the fluoride-containing phosphoric acid is constant, the selectivity is not constant regardless of the temperature of the fluoride-containing phosphoric acid, but increases or decreases depending on the temperature of the fluoride-containing phosphoric acid. Therefore, by controlling the temperature of the fluoride-containing phosphoric acid, the silicon oxide film and silicon nitride film can be etched so that the selectivity is 1 or near, or the silicon oxide film and silicon nitride film can be etched so that the selectivity is greater than or less than 1.

[0018] The fluoride is ammonium fluoride or ammonium hydrogen difluoride.

[0019] According to this method, fluoride-containing phosphoric acid containing ammonium fluoride or ammonium hydrogen difluoride at an etching temperature is brought into contact with a silicon oxide film and a silicon nitride film formed on a substrate. This allows the silicon oxide film and the silicon nitride film to be etched at equal or nearly equal etching rates. If the fluoride is an alkali metal fluoride such as sodium fluoride (NaF) or potassium fluoride (KF), the substrate may be contaminated with metal. If the fluoride is ammonium fluoride or ammonium hydrogen difluoride, there is no such risk. Therefore, the silicon oxide film and the silicon nitride film can be etched as described above while preventing a decrease in the cleanliness of the substrate.

[0020] A selectivity ratio, which represents a ratio of an etching rate of the silicon nitride film etched in the phosphoric acid supplying step to an etching rate of the silicon oxide film etched in the phosphoric acid supplying step, is within a range of 0.9 to 1.1. This range of selectivity ratio is an example of a range of selectivity ratio when the etching temperature is equal to or close to a constant rate temperature.

[0021] According to this method, the temperature of the fluoride-containing phosphoric acid is adjusted so that the selectivity (etching rate of silicon nitride film / etching rate of silicon oxide film) is within a range of 0.9 to 1.1, and the fluoride-containing phosphoric acid at this temperature is brought into contact with the silicon oxide film and silicon nitride film formed on the substrate. The silicon oxide film and silicon nitride film are etched with a selectivity within a range of 0.9 to 1.1. This makes it possible to prevent the silicon oxide film from being hardly etched, as occurs when the silicon oxide film and silicon nitride film are etched with phosphoric acid not containing fluoride, while the silicon nitride film is etched at a rate higher than the etching rate of the silicon oxide film.

[0022] The substrate includes a plurality of the silicon oxide films and a plurality of the silicon nitride films stacked in a thickness direction of the substrate so that the silicon oxide films and the silicon nitride films are alternately arranged, and holes recessed from an outermost surface of the substrate in the thickness direction and penetrating the plurality of the silicon oxide films and the plurality of the silicon nitride films in the thickness direction, and the phosphoric acid supplying step includes a step of contacting the plurality of the silicon oxide films and the plurality of the silicon nitride films exposed in the holes with the fluoride-containing phosphoric acid at the etching temperature.

[0023] According to this method, fluoride-containing phosphoric acid at an etching temperature is supplied into a hole penetrating a plurality of silicon oxide films and a plurality of silicon nitride films in the thickness direction of the substrate. The fluoride-containing phosphoric acid comes into contact with the plurality of silicon oxide films and the plurality of silicon nitride films constituting the inner peripheral surface of the hole, and etches them. If the longitudinal cross section of the inner peripheral surface of the hole before etching (a cross section cut along a plane parallel to the thickness direction of the substrate and including the center line of the hole) is linear, etching the inner peripheral surface of the hole with phosphoric acid that does not contain fluoride may cause the longitudinal cross section of the inner peripheral surface of the hole to change to a wavy line. Supplying fluoride-containing phosphoric acid at an etching temperature into the hole can prevent or mitigate such a change.

[0024] The diameter of the hole varies depending on the position in the thickness direction of the substrate.

[0025] According to this method, fluoride-containing phosphoric acid at an etching temperature is supplied into a hole whose diameter changes depending on the position in the thickness direction of the substrate. This allows the inner surface of the hole to be etched with fluoride-containing phosphoric acid while maintaining the vertical cross-sectional shape of the inner surface of the hole. When the inner surface of the hole is etched with an etching solution, the etching solution is less likely to be replaced as the hole approaches the bottom, so the etching rate tends to decrease as the hole approaches the bottom. If the diameter of the hole increases as the hole approaches the bottom, etching the inner surface of the hole with fluoride-containing phosphoric acid can reduce the variation in the diameter of the hole while maintaining the vertical cross-sectional shape of the inner surface of the hole.

[0026] The inner circumferential surface of the hole may have a shape in which the diameter of the hole decreases or increases continuously or stepwise from the outermost surface of the substrate to the bottom of the hole as the hole approaches the bottom, or the inner circumferential surface of the hole may include at least one of a portion where the diameter of the hole decreases continuously or stepwise as the hole approaches the bottom, and a portion where the diameter of the hole increases continuously or stepwise as the hole approaches the bottom.

[0027] The substrate processing method further includes an inner surface protection step of covering a portion of the inner surface of the hole in the thickness direction of the substrate with a solid, liquid, or semi-solid protective substance that protects the silicon oxide film and the silicon nitride film from the fluoride-containing phosphoric acid, and the phosphoric acid supply step includes a step of contacting the remaining portion of the inner surface of the hole that is not covered with the protective substance with the fluoride-containing phosphoric acid at the etching temperature, while protecting the portion of the inner surface of the hole from the fluoride-containing phosphoric acid at the etching temperature with the protective substance.

[0028] According to this method, before supplying fluoride-containing phosphoric acid at an etching temperature into a hole whose diameter changes depending on the position in the thickness direction of the substrate, a part of the inner surface of the hole in the thickness direction of the substrate is entirely covered with a protective material, and then the remaining part of the inner surface of the hole that is not covered with the protective material is contacted with fluoride-containing phosphoric acid at the etching temperature, thereby selectively etching the remaining part of the inner surface of the hole and intentionally changing the shape of the hole.

[0029] If the diameter of a hole "decreases" from the top surface of the substrate to the bottom of the hole, the variation in the diameter of the hole can be reduced by protecting the inlet portion of the inner periphery of the hole with a protective material and etching the bottom portion of the inner periphery of the hole with fluoride-containing phosphoric acid. On the other hand, if the diameter of a hole "increases" from the top surface of the substrate to the bottom of the hole, the variation in the diameter of the hole can be reduced by protecting the bottom portion of the inner periphery of the hole with a protective material and etching the inlet portion of the inner periphery of the hole with fluoride-containing phosphoric acid.

[0030] When the fluoride-containing phosphoric acid is supplied to the substrate, the protective substance may be any of solid, liquid, and semi-solid, so long as a part of the inner surface of the hole in the thickness direction of the substrate is kept covered with the protective substance. The protective substance may be a cylindrical protective film coaxial with the inner surface of the hole, or a protective plug that fills the entire inner area of ​​the inner surface of the hole. The remaining part of the inner surface of the hole that is not covered with the protective substance may be a part closer to the bottom of the hole than the protective substance, or a part closer to the inlet of the hole (the outermost surface of the substrate) than the protective substance.

[0031] The substrate processing method further includes a substrate heating step of heating the substrate to maintain the substrate at a constant temperature before the fluoride-containing phosphoric acid at the etching temperature is brought into contact with the silicon oxide film and the silicon nitride film formed on the substrate.

[0032] According to this method, before the substrate is contacted with the fluoride-containing phosphoric acid that is maintained at the etching temperature by heating, the substrate is heated and maintained at a constant temperature. This allows the silicon oxide film and the silicon nitride film to be etched in a short time compared to the case where the fluoride-containing phosphoric acid at the etching temperature is supplied to the substrate at room temperature. Furthermore, since the temperature of the substrate before contacting with the fluoride-containing phosphoric acid is stabilized, when multiple substrates are contacted with the fluoride-containing phosphoric acid at the etching temperature in sequence, the etching amount between the multiple substrates can be stabilized.

[0033] Another embodiment of the present invention for achieving the above object provides a substrate processing apparatus including: a heater for heating fluoride-containing phosphoric acid, which is phosphoric acid containing fluoride, to maintain the fluoride-containing phosphoric acid at an etching temperature that is equal to or close to the isokinetic temperature at which the etching rates of silicon oxide film and silicon nitride film are equal at the fluoride concentration in the fluoride-containing phosphoric acid; and a chemical nozzle for discharging the fluoride-containing phosphoric acid at the etching temperature, and etching the silicon oxide film and silicon nitride film formed on the substrate by contacting the discharged fluoride-containing phosphoric acid at the etching temperature with the silicon oxide film and silicon nitride film formed on the substrate. This apparatus can achieve the same effect as the above-mentioned substrate processing method. [Brief description of the drawings]

[0034] [Figure 1A-D] 1A to 1C are cross-sectional views of a substrate for explaining an example of substrate processing according to the embodiment. [Figure 1E-H] 1A to 1C are cross-sectional views of a substrate for explaining an example of substrate processing according to the embodiment. [Diagram 2] 1A and 1B are cross-sectional views of a substrate showing images of the inner periphery of a memory hole before and after etching with fluoride-free phosphoric acid. [Diagram 3] 1A and 1B are cross-sectional views of a substrate showing images of the inner surface of a memory hole before and after etching with fluoride-containing phosphoric acid that contains fluoride. [Figure 4]1 is a line graph showing the relationship between the concentration of fluoride in fluoride-containing phosphoric acid and the etching rate of a silicon oxide film and a silicon nitride film. [Diagram 5] 1 is a line graph showing the relationship between the concentration of fluoride in fluoride-containing phosphoric acid and the etching rate of a silicon oxide film and a silicon nitride film. [Figure 6] 1 is a line graph showing the relationship between the temperature of fluoride-containing phosphoric acid and the etching rate of a silicon oxide film and a silicon nitride film. [Figure 7] 1 is a line graph showing the relationship between the temperature of fluoride-containing phosphoric acid and the etching rate of a silicon oxide film and a silicon nitride film. [Figure 8] 1 is a schematic plan view showing a layout of a batch-type substrate processing apparatus according to an embodiment of the present invention; [Figure 9] FIG. 2 is a schematic diagram showing an example of a vertical cross section of a chemical solution treatment tank. [Figure 10] FIG. 11 is a schematic view showing another example of a vertical cross section of the chemical solution treatment tank. [Figure 11A] 1 is a schematic plan view showing a layout of a single-wafer type substrate processing apparatus according to an embodiment of the present invention; [Figure 11B] FIG. 2 is a schematic side view of a single-wafer type substrate processing apparatus. [Figure 12] FIG. 2 is a schematic diagram showing the inside of the processing unit as viewed horizontally. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0036] 1A, 1B, 1C, 1D, 1E, 1F, 1G, and 1H are cross-sectional views of a substrate W for explaining an example of processing of the substrate W according to the present embodiment.

[0037] 1A to 1H show a cross section of the substrate W cut along a plane perpendicular to the surface of the substrate W. In the following, an example will be described in which the processing of the substrate W is part of a manufacturing process for a three-dimensional NAND flash memory. In the following description, unless otherwise specified, phosphoric acid means an aqueous phosphoric acid solution. However, the concentration of phosphoric acid is determined by the concentration of the phosphoric acid compound (H 3 PO 4 ) means the concentration of

[0038] 1A, the substrate W includes a plate-shaped base material 101 such as a silicon wafer, a laminated film 102 formed on the base material 101, and a memory hole 104 recessed in the thickness direction Dt of the substrate W from the outermost surface of the laminated film 102, which corresponds to the outermost surface 103 of the substrate W. The laminated film 102 is a part that constitutes the memory cell array of the three-dimensional NAND flash memory. The memory cell array is a part that includes a plurality of memory cells that are three-dimensionally arranged in three orthogonal directions.

[0039] The laminated film 102 includes a plurality of silicon oxide films O1 and a plurality of silicon nitride films N1 that are laminated in a thickness direction Dt of the substrate W such that the silicon oxide films O1, which are thin films of silicon oxide, and the silicon nitride films N1, which are thin films of silicon nitride, are alternately arranged. The memory hole 104 penetrates the plurality of silicon oxide films O1 and the plurality of silicon nitride films N1 in the thickness direction Dt of the substrate W. The memory hole 104 is formed by dry etching such as reactive ion etching.

[0040] At least a part of the inner peripheral surface 105 of the memory hole 104 is composed of the inner peripheral surfaces of multiple silicon oxide films O1 and multiple silicon nitride films N1 that are continuous in the thickness direction Dt of the substrate W such that the inner peripheral surfaces of the silicon oxide films O1 and the silicon nitride films N1 alternate with each other. Fig. 1A shows an example in which the diameter of the memory hole 104 continuously decreases from the outermost surface 103 of the substrate W to the bottom of the memory hole 104 as it approaches the bottom of the memory hole 104. The cross section of the memory hole 104, that is, the cross section of the memory hole 104 along a plane perpendicular to the thickness direction Dt of the substrate W, is circular.

[0041] As shown in Fig. 1B, in one example of processing of the substrate W according to this embodiment, a filling liquid 111 is supplied to the substrate W in which a memory hole 104 is formed, and the memory hole 104 is filled with the filling liquid 111. Thereafter, as shown in Fig. 1C, the filling liquid 111 in the memory hole 104 is changed into a filling substance 112, and the memory hole 104 is filled with the filling substance 112. Fig. 1C shows a state in which the entire memory hole 104 is filled with the filling substance 112. The filling substance 112 may be solid, or may be semi-solid including a liquid.

[0042] The filling liquid 111 changes to a solid or semi-solid state by, for example, precipitation, coagulation, or solidification. Precipitation means that the concentration of the solute dissolved in the solvent changes to a solid state as a result of the evaporation of the solvent causing the concentration of the solute to exceed the saturation concentration. Coagulation means that the liquid phase changes to a solid phase as a result of the temperature decreasing to below the freezing point. Solidification means that the liquid phase changes to a solid state through a chemical change caused by the supply of energy such as heat or light. After the filling liquid 111 is supplied to the substrate W, the filling liquid 111 is changed to a solid or semi-solid state by precipitation, coagulation, or solidification, and the filling liquid 111 is changed to a filling substance 112.

[0043] The filling liquid 111 may be a solution containing a solute and a solvent. The solute may be at least one selected from the group consisting of a heat-sensitive water-soluble resin, an acrylic resin, a phenolic resin, an epoxy resin, a melamine resin, a urea resin, an unsaturated polyester resin, an alkyd resin, a polyurethane, a polyimide, a polyethylene, a polypropylene, a polyvinyl chloride, a polystyrene, a polyvinyl acetate, a polytetrafluoroethylene, an acrylonitrile butadiene styrene resin, an acrylonitrile styrene resin, a polyamide, a polyacetal, a polycarbonate, a polyvinyl alcohol, a modified polyphenylene ether, a polybutylene terephthalate, a polyethylene terephthalate, a polyphenylene sulfide, a polysulfone, a polyether ether ketone, and a polyamide imide. The heat-sensitive water-soluble resin is a resin that is poorly soluble or insoluble in water before being heated to a predetermined temperature or higher, and changes to become water-soluble when heated to the temperature or higher. The solvent preferably has a higher volatility than water. It is preferable to use PGEE (propylene glycol monoethyl ether) as the solvent.

[0044] The filling liquid 111 may contain a sublimable substance. As the sublimable substance, various substances that have a high vapor pressure at 5°C to 35°C and change from a solid phase to a gas phase without passing through a liquid phase are used. As the sublimable substance, for example, hexamethylenetetramine, 1,3,5-trioxane, 1-pyrrolidinecarbodithioic acid ammonium, metaldehyde, paraffin having about 20 to 48 carbon atoms, t-butanol, paradichlorobenzene, naphthalene, L-menthol, fluorohydrocarbon compounds, etc. can be used. In particular, as the sublimable substance, a fluorohydrocarbon compound can be used. It is particularly preferable to use 1,1,2,2,3,3,4-heptafluorocyclopentane as the sublimable substance.

[0045] The solvent may be, for example, at least one selected from the group consisting of pure water (deionized water: DIW), aliphatic hydrocarbons, aromatic hydrocarbons, esters, alcohols, and ethers. Specifically, examples of the solvent include at least one selected from the group consisting of pure water, methanol, ethanol, IPA, butanol, ethylene glycol, propylene glycol, NMP (N-methyl-2-pyrrolidone), DMF (N,N-dimethylformamide), DMA (dimethylacetamide), DMSO (dimethylsulfoxide), hexane, toluene, PGMEA (propylene glycol monomethyl ether acetate), PGME (propylene glycol monomethyl ether), PGPE (propylene glycol monopropyl ether), PGEE (propylene glycol monoethyl ether), GBL (γ-butyrolactone), acetylacetone, 3-pentanone, 2-heptanone, ethyl lactate, cyclohexanone, dibutyl ether, HFE (hydrofluoroether), ethyl nonafluoroisobutyl ether, ethyl nonafluorobutyl ether, and m-xylene hexafluoride.

[0046] After the filling material 112 is formed in the memory hole 104, as shown in Fig. 1D, a removal liquid 113 that dissolves the filling material 112 is supplied to the substrate W, and the filling material 112 in the memory hole 104 is removed by the removal liquid 113 while leaving the filling material 112 on the bottom side of the memory hole 104. The removal liquid 113 supplied to the substrate W comes into contact with the filling material 112 in the memory hole 104, and dissolves the filling material 112 from the entrance side of the memory hole 104 toward the bottom of the memory hole 104. As a result, the end face of the filling material 112 moves toward the bottom side of the memory hole 104, and the height of the filling material 112 gradually decreases.

[0047] As the removal liquid 113, for example, organic solvents such as thinner, toluene, acetates, alcohols, and glycols, and acidic liquids such as acetic acid, formic acid, and hydroxyacetic acid can be used. In particular, it is preferable to use a solvent that is compatible with water-based liquids as the removal liquid 113. For example, it is preferable to use isopropyl alcohol (IPA) as the removal liquid 113.

[0048] When the filling material 112 has been removed from the range from the entrance of the memory hole 104 to the middle of the memory hole 104 and a time has elapsed during which the filling material 112 remains in the range from the middle of the memory hole 104 to the bottom of the memory hole 104, the removing liquid 113 is removed from the substrate W. The removing liquid 113 may be removed by replacing the removing liquid 113 in contact with the substrate W with a liquid such as pure water or a protective liquid 114 described below. The distance from the entrance of the memory hole 104 to the middle of the memory hole 104 may be equal to or different from the distance from the middle of the memory hole 104 to the bottom of the memory hole 104.

[0049] The filling material 112 remaining in the memory hole 104 after the removal liquid 113 is removed from the substrate W is defined as the remaining filling material 112r. The part of the inner surface 105 of the memory hole 104 that is not in contact with the remaining filling material 112r is defined as the inlet part 105e of the inner surface 105 of the memory hole 104, and the part of the inner surface 105 of the memory hole 104 that is in contact with the remaining filling material 112r is defined as the bottom part 105b of the inner surface 105 of the memory hole 104. At least a part of the inlet part 105e is composed of the inner surfaces of the multiple silicon oxide films O1 and the inner surfaces of the multiple silicon nitride films N1. At least a part of the bottom part 105b is composed of the inner surfaces of the other multiple silicon oxide films O1 and the inner surfaces of the other multiple silicon nitride films N1.

[0050] 1E, a protective liquid 114 is supplied to the substrate W, and a protective film 115, which is an example of a protective material, is formed on the inlet side portion 105e of the inner circumferential surface 105 of the memory hole 104. Since the filling material 112 remains on the bottom side of the memory hole 104, when the protective liquid 114 is supplied to the substrate W, the inlet side region of the memory hole 104, i.e., the region on the inlet side of the memory hole 104 relative to the remaining filling material 112r in the memory hole 104, is filled with the protective liquid 114, and the inlet side portion 105e of the inner circumferential surface 105 of the memory hole 104 and the end face of the remaining filling material 112r come into contact with the protective liquid 114.

[0051] The protection liquid 114 is, for example, a liquid of a water repellent agent that makes silicon (Si) itself and compounds containing silicon hydrophobic. Typically, the water repellent agent is a silane coupling agent. In one example, the silane coupling agent includes at least one of HMDS (hexamethyldisilazane), TMS (tetramethylsilane), fluorinated alkylchlorosilane, alkyldisilazane, and a non-chloro water repellent agent. The non-chloro water repellent agent includes, for example, at least one of dimethylsilyldimethylamine, dimethylsilyldiethylamine, hexamethyldisilazane, tetramethyldisilazane, bis(dimethylamino)dimethylsilane, N,N-dimethylaminotrimethylsilane, N-(trimethylsilyl)dimethylamine, and an organosilane compound.

[0052] The protective liquid 114 adheres to the multiple silicon oxide films O1 and multiple silicon nitride films N1 constituting the inlet side portion 105e of the inner circumferential surface 105 of the memory hole 104, and forms a protective film 115 on the inlet side portion 105e of the inner circumferential surface 105 of the memory hole 104. The protective film 115 is a cylindrical liquid film coaxial with the inner circumferential surface 105 of the memory hole 104, and contacts the entire area of ​​the inlet side portion 105e of the inner circumferential surface 105 of the memory hole 104. In FIG. 1E, for ease of understanding, a boundary is shown between the protective liquid 114 and the protective film 115, but in reality, such a boundary does not exist.

[0053] When the protective liquid 114 comes into contact with the entrance portion 105e of the inner circumferential surface 105 of the memory hole 104 and the protective film 115 is formed on the entrance portion 105e of the inner circumferential surface 105 of the memory hole 104, the protective liquid 114 is removed from the substrate W. The protective liquid 114 may be removed by replacing the protective liquid 114 with a liquid such as pure water. Even after the protective liquid 114 is removed from the substrate W, the protective liquid 114 remains on the entrance portion 105e of the inner circumferential surface 105 of the memory hole 104.

[0054] After the protection liquid 114 is brought into contact with the inlet portion 105e of the inner circumferential surface 105 of the memory hole 104, as shown in FIG. 1F, the filling substance 112 is removed from the bottom region of the memory hole 104, that is, the region occupied by the remaining filling substance 112r in the memory hole 104, while leaving the protection film 115 on the inlet portion 105e of the inner circumferential surface 105 of the memory hole 104. The removal of the remaining filling substance 112r may be performed by supplying a removal liquid 113 to the substrate W as shown in FIG. 1F. In this case, the protection liquid 114 in the memory hole 104 may be replaced with the removal liquid 113. The removal of the remaining filling substance 112r may be performed by heating the substrate W. If the remaining filling substance 112r contains a sublimable substance, the remaining filling substance 112r may be sublimated by heating the substrate W.

[0055] As shown in FIG. 1F, when the remaining filling material 112r is removed from the memory hole 104, the bottom portion 105b of the inner circumferential surface 105 of the memory hole 104 is exposed from the filling material 112, with the inlet portion 105e of the inner circumferential surface 105 of the memory hole 104 being covered with the protective film 115. As shown in FIG. 1G, in this state, fluoride-containing phosphoric acid is supplied to the substrate W. FIG. 1G shows that the fluoride contained in the fluoride-containing phosphoric acid is ammonium fluoride (NH 4 The fluoride-containing phosphoric acid supplied to the substrate W enters the memory hole 104 from the entrance of the memory hole 104 and passes through the inside of the cylindrical protective film 115. As a result, the bottom region of the memory hole 104 and the inner region of the protective film 115 are filled with the fluoride-containing phosphoric acid.

[0056] Fluoride-containing phosphoric acid is phosphoric acid containing fluoride (strictly speaking, an aqueous phosphoric acid solution containing fluoride). Fluoride-containing phosphoric acid is an example of a chemical solution containing a substance that chemically reacts with the substrate W. Fluoride-containing phosphoric acid is also an example of an etching solution for etching the substrate W. The fluoride contained in the fluoride-containing phosphoric acid may be a solid fluoride dissolved in phosphoric acid, or may be a fluoride contained in a fluoride-containing liquid (a fluoride liquid or a solution in which fluoride is dissolved) mixed with phosphoric acid.

[0057] The fluoride contained in fluoride-containing phosphoric acid is ammonium fluoride (NH 4 F) or ammonium difluoride (NH 4 HF 2 ) When the fluoride is ammonium fluoride, the concentration of the fluoride in the fluoride-containing phosphoric acid is 0.15 to 1.5 wt% (mass percent concentration). The concentration of phosphoric acid before adding fluoride (concentration of phosphoric acid in the phosphoric acid aqueous solution) is 85%. The concentration of phosphoric acid and the concentration of fluoride are not limited to those mentioned above.

[0058] The silicon oxide films O1 and silicon nitride films N1 constituting the inlet portion 105e of the inner peripheral surface 105 of the memory hole 104 are protected from the fluoride-containing phosphoric acid by the protective film 115. On the other hand, the silicon oxide films O1 and silicon nitride films N1 constituting the bottom portion 105b of the inner peripheral surface 105 of the memory hole 104 come into contact with the fluoride-containing phosphoric acid and are etched by the fluoride-containing phosphoric acid. As described later, the fluoride-containing phosphoric acid is supplied to the substrate W under processing conditions in which the silicon oxide film O1 and the silicon nitride film N1 are etched at equal or nearly equal etching rates. Therefore, while the bottom portion 105b of the inner peripheral surface 105 of the memory hole 104 is etched, the inlet portion 105e of the inner peripheral surface 105 of the memory hole 104 is not etched or is hardly etched.

[0059] The bottom portion 105b of the inner peripheral surface 105 of the memory hole 104 is etched at any position in the circumferential direction of the memory hole 104, and is etched at any position in the depth direction of the memory hole 104 that coincides with the thickness direction Dt of the substrate W. Therefore, although the height of the bottom portion 105b of the inner peripheral surface 105 of the memory hole 104 (the shortest distance in the thickness direction Dt of the substrate W from the bottom of the memory hole 104 to the protective film 115) does not change or hardly changes, the diameter of the bottom portion 105b of the inner peripheral surface 105 of the memory hole 104 increases at any position in the thickness direction Dt of the substrate W. The bottom portion 105b of the inner peripheral surface 105 of the memory hole 104 after etching is cylindrical and coaxial with the bottom portion 105b of the inner peripheral surface 105 of the memory hole 104 before etching.

[0060] FIG. 1A shows an example in which the memory hole 104 tapers toward the bottom of the memory hole 104. In this example, before the fluoride-containing phosphoric acid is supplied to the substrate W, the diameter of the memory hole 104 is maximum near the entrance of the memory hole 104 and is minimum near the bottom of the memory hole 104. When the fluoride-containing phosphoric acid is supplied to the substrate W, the diameter of the entrance side portion 105e of the inner peripheral surface 105 of the memory hole 104 does not change or changes little, while the diameter of the bottom side portion 105b of the inner peripheral surface 105 of the memory hole 104 increases due to etching of the silicon oxide film O1 and the silicon nitride film N1. The minimum value of the diameter of the memory hole 104 approaches the maximum value of the diameter of the memory hole 104. This reduces the difference between the maximum and minimum values ​​of the diameter of the memory hole 104.

[0061] When a predetermined time has elapsed since the supply of the fluoride-containing phosphoric acid to the substrate W started, the fluoride-containing phosphoric acid is removed from the substrate W. The fluoride-containing phosphoric acid may be removed by replacing the fluoride-containing phosphoric acid in contact with the substrate W with a liquid such as a rinse liquid. The protective film 115 may be removed by heating the substrate W or irradiating the substrate W with ultraviolet light after or while removing the fluoride-containing phosphoric acid. The protective film 115 may be left as long as it does not affect the characteristics of the three-dimensional NAND flash memory.

[0062] After the fluoride-containing phosphoric acid is removed from the substrate W, a thin film 116, which is a part of the three-dimensional NAND flash memory, is deposited on the entire inner surface 105 of the memory hole 104 by vapor deposition such as chemical vapor deposition, as shown in FIG. 1H. The thin film 116 in contact with the inner surface 105 of the memory hole 104 is a part that constitutes a plurality of memory cells arranged in the thickness direction Dt of the substrate W. This thin film 116 may be a conductive film such as a polysilicon film, or an insulating film such as a silicon oxide film. The silicon nitride film N1 may be a sacrificial film that is replaced with a thin film such as a metal film after the thin film 116 is deposited on the inner surface 105 of the memory hole 104.

[0063] The series of steps from forming the memory hole 104 until depositing the thin film 116 on the inner surface 105 of the memory hole 104 is a hole shape modification step in which the shape of the memory hole 104 is modified by wet etching. The hole shape modification step is performed by a wet process in which a processing liquid is brought into contact with the substrate W. In contrast, the memory hole 104 is formed by dry etching, which is an example of a dry process. The thin film 116 in contact with the inner surface 105 of the memory hole 104 is also formed by vapor phase deposition, which is an example of a dry process.

[0064] The hole shape correcting step may be performed by one substrate processing apparatus 1 (see FIG. 8 and FIG. 11) or by a plurality of substrate processing apparatuses 1. The hole shape correcting step may be performed by a batch type substrate processing apparatus 1 that processes a plurality of substrates W collectively, or a single-wafer type substrate processing apparatus 1 that processes a plurality of substrates W one by one, or by a batch type substrate processing apparatus 1 and a single-wafer type substrate processing apparatus 1. A part of the hole shape correcting step may be performed by a dry process. For example, a protective gas, instead of the protective liquid 114, may be brought into contact with the inlet side portion 105e of the inner circumferential surface 105 of the memory hole 104 to form a solid, liquid, or semi-solid protective film 115 on the inlet side portion 105e of the inner circumferential surface 105 of the memory hole 104 using a substance contained in the protective gas.

[0065] Next, the cross sections of the substrate W before and after etching will be described.

[0066] Fig. 2 is a cross-sectional view of a substrate W showing images of an inner peripheral surface 105 of a memory hole 104 before and after etching with phosphoric acid not containing fluoride (hereinafter simply referred to as "phosphoric acid"). Fig. 3 is a cross-sectional view of a substrate W showing images of an inner peripheral surface 105 of a memory hole 104 before and after etching with fluoride-containing phosphoric acid containing fluoride.

[0067] 2 and 3, the inner circumferential surface 105 of the memory hole 104 before etching is indicated by a two-dot chain line, and the inner circumferential surface 105 of the memory hole 104 after etching is indicated by a solid line. The shapes of the inner circumferential surface 105 of the memory hole 104 before and after etching are merely images, and may differ from the actual shapes. FIG. 3 shows a case where the fluoride contained in the fluoride-containing phosphoric acid is ammonium fluoride (NH 4 F) is shown below.

[0068] At least a portion of the inner circumferential surface 105 of the memory hole 104 is composed of the inner circumferential surfaces of a plurality of silicon oxide films O1 and a plurality of silicon nitride films N1 that are continuous in the thickness direction Dt of the substrate W such that the inner circumferential surfaces of the silicon oxide films O1 and the silicon nitride films N1 alternate with each other. When phosphoric acid is supplied to the memory hole 104, the silicon oxide film O1 is not or barely etched by the phosphoric acid, whereas the silicon nitride film N1 is etched by the phosphoric acid at an etching rate higher than the etching rate of the silicon oxide film O1.

[0069] As shown in FIG. 2, when the inner peripheral surface 105 of the memory hole 104 is etched with phosphoric acid, the diameter of the memory hole 104 does not change or hardly changes at the positions of the multiple silicon oxide films O1, but increases at the positions of the multiple silicon nitride films N1. As shown by the two-dot chain line in FIG. 2, when the diameter of the memory hole 104 before etching is uniform, when the inner peripheral surface 105 of the memory hole 104 is etched with phosphoric acid, the vertical cross section (cross section cut by a plane parallel to the thickness direction Dt of the substrate W and including the center line of the memory hole 104) of the inner peripheral surface 105 of the memory hole 104 changes from a straight line to a wavy line. In this case, the inner peripheral surface 105 of the memory hole 104 changes to a cylindrical shape in which the diameter decreases at the positions of the multiple silicon oxide films O1 and increases at the positions of the multiple silicon nitride films N1.

[0070] A thin film 116 (see FIG. 1H) that will become a part of the three-dimensional NAND flash memory is formed on the inner circumferential surface 105 of the memory hole 104. It is preferable that the vertical cross section of the inner circumferential surface 105 of the memory hole 104 has as few undulations as possible. In addition, it is preferable that the diameter of the memory hole 104 is as uniform as possible. FIG. 3 shows an example in which the diameter of the memory hole 104 is uniform even after etching, and the vertical cross section of the inner circumferential surface 105 of the memory hole 104 has as few undulations as possible even after etching. In this example, the inner circumferential surface 105 of the memory hole 104 is etched while the vertical cross section of the inner circumferential surface 105 of the memory hole 104 is maintained linear.

[0071] As described below, the fluoride-containing phosphoric acid is supplied to the inner surface 105 of the memory hole 104 under processing conditions in which the silicon oxide film O1 and the silicon nitride film N1 are etched at equal or approximately equal etching rates. This allows not only the silicon nitride film N1 but also the silicon oxide film O1 to be etched at a sufficient etching rate, and prevents the formation of multiple ring-shaped depressions recessed in the surface direction Dp of the substrate W (direction perpendicular to the thickness direction Dt of the substrate W) at the positions of multiple silicon nitride films N1 on the inner surface 105 of the memory hole 104. Even if such depressions are formed, the depressions can be made shallow.

[0072] Next, the relationship between the etching rate and the fluoride concentration or the temperature of the fluoride-containing phosphoric acid will be described.

[0073] 4 to 7 are line graphs showing measured etching rates when a silicon oxide film O1 and a silicon nitride film are etched using fluoride-containing phosphoric acid.

[0074] 4 to 7 show the etching rates when a silicon oxide film and a silicon nitride film are etched using a solution in which ammonium fluoride is added to 85% phosphoric acid (a phosphoric acid aqueous solution with a phosphoric acid concentration of 85%). In Figs. 4 to 7, the vertical axis shows the etching rate, and the horizontal axis shows the concentration of ammonium fluoride or the temperature of the fluoride-containing phosphoric acid. The etching rate represents the amount of film thickness reduction per unit time.

[0075] "Figure 4" is a line graph showing the relationship between the etching rate of silicon oxide film and silicon nitride film and the concentration of ammonium fluoride in fluoride-containing phosphoric acid when the fluoride-containing phosphoric acid is at "120°C." "Figure 5" is a line graph showing the relationship between the etching rate of silicon oxide film and silicon nitride film and the concentration of ammonium fluoride in fluoride-containing phosphoric acid when the fluoride-containing phosphoric acid is at "130°C."

[0076] FIG. 6 is a line graph showing the relationship between the etching rate of silicon oxide film and silicon nitride film and the temperature of fluoride-containing phosphoric acid when the concentration of ammonium fluoride in the fluoride-containing phosphoric acid is 0.15 wt%. FIG. 7 is a line graph showing the relationship between the etching rate of silicon oxide film and silicon nitride film and the temperature of fluoride-containing phosphoric acid when the concentration of ammonium fluoride in the fluoride-containing phosphoric acid is 0.3 wt%. The dashed line in FIG. 7 shows the predicted change in the etching rate of the silicon oxide film, and the dashed line in FIG. 7 shows the predicted change in the etching rate of the silicon nitride film.

[0077] As shown in Figure 4, when the fluoride-containing phosphoric acid was at 120°C, the etching rates of the silicon oxide film and the silicon nitride film increased as the concentration of ammonium fluoride increased. When the ammonium fluoride concentration was 0.15 wt% or less, the difference between the etching rates of the silicon oxide film and the silicon nitride film was smaller than when the concentration exceeded 0.15 wt%. When the ammonium fluoride concentration exceeded 0.15 wt%, the etching rate of the silicon oxide film was higher than that of the silicon nitride film, and the difference between the two increased as the concentration of ammonium fluoride increased.

[0078] As shown in Figure 5, when the fluoride-containing phosphoric acid was at 130°C, the etching rates of the silicon oxide film and the silicon nitride film increased as the concentration of ammonium fluoride increased. When the ammonium fluoride concentration was 0.15 wt% or less, the etching rate of the silicon oxide film was lower than that of the silicon nitride film. When the ammonium fluoride concentration was 0.3 wt% or less, the difference between the etching rates of the silicon oxide film and the silicon nitride film was smaller than when the ammonium fluoride concentration exceeded 0.3 wt%. When the ammonium fluoride concentration exceeded 0.3 wt%, the etching rate of the silicon oxide film was higher than that of the silicon nitride film, and the difference between the two increased as the concentration of ammonium fluoride increased.

[0079] As shown in Figure 6, when the concentration of ammonium fluoride was 0.15 wt%, the etching rate of the silicon oxide film was almost constant when the temperature of the fluoride-containing phosphoric acid was below 120°C, and decreased with increasing temperature when the temperature of the fluoride-containing phosphoric acid was above 120°C. The etching rate of the silicon nitride film was almost constant when the temperature of the fluoride-containing phosphoric acid was below 90°C, and increased with increasing temperature when the temperature of the fluoride-containing phosphoric acid was above 90°C.

[0080] As shown in Figure 6, the etching rate of silicon oxide films was higher than that of silicon nitride films when the temperature of the fluoride-containing phosphoric acid was below 120°C, and the etching rate of silicon oxide films was lower than that of silicon nitride films when the temperature of the fluoride-containing phosphoric acid exceeded 120°C. The difference between the etching rates of silicon oxide films and silicon nitride films decreased as the temperature of the fluoride-containing phosphoric acid approached 120°C.

[0081] As shown in FIG. 7, when the concentration of ammonium fluoride is 0.3 wt%, the etching rate of the silicon oxide film increases with increasing temperature when the temperature of the fluoride-containing phosphoric acid is less than 120° C., and decreases with increasing temperature when the temperature of the fluoride-containing phosphoric acid is 120° C. or more and 130° C. or less. The etching rate of the silicon nitride film increases with increasing temperature when the temperature of the fluoride-containing phosphoric acid is 80° C. or more and 130° C. or less. According to the measurement results shown in FIG. 6, when the temperature of the fluoride-containing phosphoric acid exceeds 130° C., the etching rate of the silicon oxide film (see the dashed line in FIG. 7) is almost constant, and the etching rate of the silicon nitride film (see the dashed line in FIG. 7) is expected to increase with increasing temperature.

[0082] As shown in Figure 7, when the temperature of the fluoride-containing phosphoric acid was below 130°C, the etching rate of the silicon oxide film was higher than that of the silicon nitride film. When the temperature of the fluoride-containing phosphoric acid was above 130°C, the etching rate of the silicon oxide film was expected to be lower than that of the silicon nitride film. The difference between the etching rates of the silicon oxide film and the silicon nitride film decreased as the temperature of the fluoride-containing phosphoric acid approached 130°C.

[0083] In FIG. 6 to FIG. 7, the temperature of the fluoride-containing phosphoric acid at which the broken line showing the etching rate of the silicon oxide film intersects with the broken line showing the etching rate of the silicon nitride film is defined as the isokinetic temperature. When the concentration of phosphoric acid in the fluoride-containing phosphoric acid and the concentration of fluoride in the fluoride-containing phosphoric acid are determined, one isokinetic temperature is determined. That is, the isokinetic temperature depends on the concentration of fluoride in the fluoride-containing phosphoric acid, and refers to the temperature of the fluoride-containing phosphoric acid at which the etching rate of the silicon oxide film and the etching rate of the silicon nitride film are equal at that concentration. Conversely, when the concentration of phosphoric acid in the fluoride-containing phosphoric acid and the temperature of the fluoride-containing phosphoric acid are determined, one isokinetic fluoride concentration is determined. The isokinetic fluoride concentration is the concentration of fluoride at which the etching rate of the silicon oxide film and the etching rate of the silicon nitride film are equal.

[0084] From the results shown in Figures 4 to 5, it can be seen that the etching rate of the silicon oxide film and the etching rate of the silicon nitride film increase when fluoride is added to phosphoric acid. In addition, from the results shown in Figures 4 to 5, it can be seen that, if the temperature of the fluoride-containing phosphoric acid is constant, the etching rate of the silicon oxide film and the etching rate of the silicon nitride film increase as the concentration of fluoride increases. As can be seen from the results shown in Figures 4 to 5, when the concentration of fluoride in the fluoride-containing phosphoric acid exceeds a certain value (0.15 wt% in Figure 4, 0.3 wt% in Figure 5), the etching rate of the silicon oxide film increases at a greater rate than the etching rate of the silicon nitride film as the concentration of fluoride in the fluoride-containing phosphoric acid increases.

[0085] From the results shown in Figures 6 to 7, it can be seen that the etching rate of the silicon oxide film does not change significantly even if the temperature of the fluoride-containing phosphoric acid changes, and the etching rate of the silicon nitride film increases as the temperature of the fluoride-containing phosphoric acid increases. In addition, from the results shown in Figures 6 to 7, it can be seen that if the concentration of fluoride in the fluoride-containing phosphoric acid is constant, there is one constant-speed temperature at which the etching rate of the silicon oxide film and the etching rate of the silicon nitride film are equal (in Figures 6 to 7, the temperature at the intersection of the broken line showing the etching rate of the silicon oxide film and the broken line showing the etching rate of the silicon nitride film). As can be seen from the results shown in Figures 6 to 7, when the concentration of fluoride in the fluoride-containing phosphoric acid increases, the constant-speed temperature also increases.

[0086] From the results shown in Fig. 4 to Fig. 7, it can be seen that if the fluoride-containing phosphoric acid is maintained at or near the isokinetic temperature while stabilizing the phosphoric acid concentration in the fluoride-containing phosphoric acid and the fluoride concentration in the fluoride-containing phosphoric acid, the silicon oxide film and the silicon nitride film can be etched at equal or nearly equal etching rates. If the fluoride concentration in the fluoride-containing phosphoric acid is increased, the etching rate of the silicon oxide film increases, and the etching rate of the silicon nitride film corresponding to the isokinetic temperature also increases. Therefore, in addition to the above conditions, if the fluoride concentration in the fluoride-containing phosphoric acid is maintained as high as possible, the silicon oxide film and the silicon nitride film can be etched at equal or nearly equal high etching rates.

[0087] In the etching of the bottom portion 105b of the inner peripheral surface 105 of the memory hole 104 described above (see FIG. 1G), fluoride-containing phosphoric acid is supplied to the substrate W at a constant etching temperature that is equal to or close to the constant rate temperature. This allows the silicon oxide film and silicon nitride film constituting the bottom portion 105b of the inner peripheral surface 105 of the memory hole 104 to be etched at equal or nearly equal high etching rates. The etching temperature may be set so that the selectivity (etching rate of silicon nitride film / etching rate of silicon oxide film) is 0.9 to 1.1 and the etching rates of the silicon oxide film and the silicon nitride film are 3 to 14 nm / min, or may be set so that at least one of the selectivity, the etching rate of the silicon oxide film, and the etching rate of the silicon nitride film is outside the above range.

[0088] So far, we have described the case where silicon oxide films and silicon nitride films are etched with fluoride-containing phosphoric acid containing ammonium fluoride, but the fluoride contained in the fluoride-containing phosphoric acid may be a fluoride other than ammonium fluoride, such as ammonium difluoride. When ammonium difluoride dissolves in water, it produces "NH 4 HF 2 ⇔NH 4 As shown by "F+HF", it decomposes into ammonium fluoride and hydrogen fluoride. Therefore, it is believed that fluoride-containing phosphoric acid containing ammonium difluoride has similar properties to fluoride-containing phosphoric acid containing ammonium fluoride.

[0089] Next, a description will be given of the substrate processing apparatus 1 that supplies fluoride-containing phosphoric acid to the substrates W. First, a batch-type substrate processing apparatus 1 will be described, and then a single-wafer-type substrate processing apparatus 1 will be described.

[0090] FIG. 8 is a schematic plan view showing a layout of a batch-type substrate processing apparatus 1 according to one embodiment of the present invention.

[0091] The substrate processing apparatus 1 is a batch-type apparatus that collectively processes a plurality of substrates W. The substrate processing apparatus 1 includes a load port LP that holds a carrier C that accommodates a disk-shaped substrate W such as a semiconductor wafer, a processing unit 2 that processes the substrate W transferred from the load port LP with a processing liquid such as a chemical liquid or a rinsing liquid, a transport system that transports the substrate W between the load port LP and the processing unit 2, and a controller 3 that controls the substrate processing apparatus 1.

[0092] The control device 3 is a computer including a memory for storing information such as programs, and a CPU (central processing unit) for controlling the substrate processing apparatus 1 in accordance with the programs stored in the memory. The control device 3 controls the substrate processing apparatus 1 to transport, process, and the like the substrate W, which will be described below. In other words, the control device 3 is programmed to transport, process, and the like the substrate W, which will be described below.

[0093] The processing unit 2 includes multiple pairs of liquid processing tanks 4 that store a processing liquid in which multiple substrates W are immersed, and a drying processing tank 8 that dries the multiple substrates W by a drying method such as reduced pressure drying. Reduced pressure drying is a drying method in which liquid adhering to the substrates W is evaporated by reducing the air pressure. The multiple pairs of liquid processing tanks 4 are aligned linearly in the depth direction of the substrate processing apparatus 1 (left and right direction on the paper in FIG. 8) in a plan view. The drying processing tank 8 is disposed between the transfer system and the multiple pairs of liquid processing tanks 4 in the depth direction of the substrate processing apparatus 1 in a plan view.

[0094] The transport system includes a carrier transport device 9 that transports carriers C between the load port LP and the processing unit 2 and accommodates multiple carriers C, and a posture changing robot 10 that loads and unloads multiple substrates W into and from the carriers C held by the carrier transport device 9 and changes the posture of the substrates W between a horizontal posture and a vertical posture. The posture changing robot 10 performs a batch assembly operation in which multiple substrates W taken out from the multiple carriers C form one batch, and a batch release operation in which the multiple substrates W included in one batch are accommodated in multiple carriers C.

[0095] The transport system further includes a main transport robot 11 which transports a plurality of substrates W between the posture changing robot 10 and the processing unit 2, and a plurality of sub-transport robots 12 which transport a plurality of substrates W between the main transport robot 11 and the processing unit 2. Fig. 8 shows an example in which two sub-transport robots 12 and two pairs of liquid treatment tanks 4 are provided. The sub-transport robot 12 transports a plurality of substrates W into and out of each of the two pairs of liquid treatment tanks 4, and transports a plurality of substrates W between the two pairs of liquid treatment tanks 4.

[0096] The main transport robot 11 receives one batch of substrates W consisting of a plurality of substrates W (e.g., 50 substrates W) from the posture changing robot 10, and transfers the received batch of substrates W to one of the multiple sub-transport robots 12. The sub-transport robot 12 immerses the batch of substrates W received from the main transport robot 11 in a processing liquid in at least one liquid processing tank 4. Thereafter, the main transport robot 11 receives the batch of substrates W from the sub-transport robot 12, and transports the received batch of substrates W into the drying processing tank 8.

[0097] The multiple liquid treatment tanks 4 include a heat treatment tank 5 that stores a heating liquid in which the multiple substrates W are immersed, a chemical liquid treatment tank 6 that stores a chemical liquid in which the multiple substrates W are immersed, and a rinsing treatment tank 7 that stores a rinsing liquid in which the multiple substrates W are immersed. The heat treatment tank 5, the chemical liquid treatment tank 6, and the rinsing treatment tank 7 are aligned in this order in a straight line in the depth direction of the substrate processing apparatus 1 in a plan view. The drying treatment tank 8 is disposed between the transport system and the rinsing treatment tank 7 in the depth direction of the substrate processing apparatus 1 in a plan view.

[0098] The heating liquid is phosphoric acid, the chemical liquid is fluoride-containing phosphoric acid, and the rinsing liquid is pure water. The heating liquid may be a liquid other than phosphoric acid, such as pure water. Similarly, the rinsing liquid may be a liquid other than pure water. For example, the rinsing liquid may be any of IPA (isopropyl alcohol), electrolytic ionized water, hydrogen water, ozone water, hydrochloric acid water with a diluted concentration (for example, about 10 to 100 ppm), and ammonia water with a diluted concentration (for example, about 10 to 100 ppm).

[0099] The substrate W with the silicon oxide film O1 and silicon nitride film N1 exposed as shown in FIG. 1F is transported to the substrate processing apparatus 1. The transport system transports one batch of substrates W to the heating treatment tank 5, the chemical treatment tank 6, the rinsing treatment tank 7, and the drying treatment tank 8 in this order. Therefore, the substrate W transported into the substrate processing apparatus 1 through the load port LP is contacted with phosphoric acid, fluoride-containing phosphoric acid, and pure water in this order and dried. By supplying the fluoride-containing phosphoric acid to the substrate W, the bottom portion 105b of the inner peripheral surface 105 of the memory hole 104 is etched as shown in FIG. 1G. The fluoride-containing phosphoric acid adhering to the substrate W is washed away by the pure water. The substrate W wetted with the pure water is dried in the drying treatment tank 8. The dried substrate W is transported out of the substrate processing apparatus 1 through the load port LP.

[0100] The phosphoric acid in the heat treatment tank 5 and the fluoride-containing phosphoric acid in the chemical treatment tank 6 are maintained at a constant temperature of 100° C. or higher. The pure water in the rinse treatment tank 7 may be at room temperature (a constant or substantially constant temperature within 15 to 30° C.), or may be maintained at a constant temperature higher or lower than room temperature. The temperature of the phosphoric acid is, for example, within a range of 100 to 150° C., and the temperature of the fluoride-containing phosphoric acid is, for example, within a range of 100 to 150° C. The temperature of the phosphoric acid may be equal to the temperature of the fluoride-containing phosphoric acid, or may be higher or lower than the temperature of the fluoride-containing phosphoric acid. Since the substrate W is heated by the phosphoric acid in the heat treatment tank 5, the substrate W having the same or substantially the same temperature as the phosphoric acid in the heat treatment tank 5 is transported to the chemical treatment tank 6.

[0101] When the heating liquid is phosphoric acid, the silicon oxide film O1 and the silicon nitride film N1 are slightly etched when they are brought into contact with the heating liquid. If such etching is undesirable, a liquid that does not etch the silicon oxide film O1 and the silicon nitride film N1, such as pure water, can be used as the heating liquid. When the heating liquid is phosphoric acid, the phosphoric acid piping 35 (see FIG. 9) for fluoride-containing phosphoric acid can be used as the piping for the heating liquid.

[0102] 9 is a schematic diagram showing an example of a vertical cross section of the chemical liquid treatment tank 6. Although not shown, the heat treatment tank 5 and the rinsing treatment tank 7 have the same configuration as the chemical liquid treatment tank 6.

[0103] The chemical solution treatment tank 6 includes an inner tank 21 for storing fluoride-containing phosphoric acid, and an outer tank 22 for storing fluoride-containing phosphoric acid overflowing from the inner tank 21. A plurality of substrates W are placed in the inner tank 21 and immersed in the fluoride-containing phosphoric acid in the inner tank 21. As a result, the fluoride-containing phosphoric acid comes into contact with the plurality of substrates W, and the plurality of substrates W are etched.

[0104] The auxiliary transport robot 12 includes a plurality of holders 23 that hold a plurality of substrates W in a vertical position, and a lifter 24 that vertically raises and lowers the plurality of holders 23 between an upper position where the plurality of substrates W held by the holders 23 are spaced above the fluoride-containing phosphoric acid in the inner bath 21, and a lower position (position shown in FIG. 9 ) where the plurality of substrates W held by the holders 23 are immersed in the fluoride-containing phosphoric acid in the inner bath 21. The plurality of substrates W held by the holders 23 enter the inner bath 21 through an opening provided at the upper end of the inner bath 21, and exit outside the inner bath 21 through the opening of the inner bath 21.

[0105] The substrate processing apparatus 1 includes a circulation heating system that heats the fluoride-containing phosphoric acid while circulating it in the chemical processing tank 6. The circulation heating system includes a circulation pipe 25 that guides the fluoride-containing phosphoric acid in the outer tank 22 toward the inner tank 21, a circulation pump 26 that sends the fluoride-containing phosphoric acid in the circulation pipe 25 toward the inner tank 21, a heater 27 that heats the fluoride-containing phosphoric acid flowing in the circulation pipe 25 to a temperature higher than room temperature, and a filter 28 that removes foreign matter from the fluoride-containing phosphoric acid flowing in the circulation pipe 25.

[0106] The circulation heating system further includes a chemical nozzle 29 that supplies fluoride-containing phosphoric acid into the inner tank 21 by discharging the fluoride-containing phosphoric acid supplied from the circulation pipe 25 from a discharge port 29p disposed in the inner tank 21, and forms an upward flow in the fluoride-containing phosphoric acid in the inner tank 21. FIG. 9 shows an example in which two chemical nozzles 29 are provided. In this example, the circulation pipe 25 includes an upstream pipe 25u extending downstream from the outer tank 22, and two downstream pipes 25d branched from the upstream pipe 25u. One chemical nozzle 29 is attached to the downstream end of one downstream pipe 25d, and the other chemical nozzle 29 is attached to the downstream end of the other downstream pipe 25d.

[0107] The inner tank 21, the outer tank 22, the circulation pipe 25, and the chemical nozzle 29 form a circulation path for circulating the fluoride-containing phosphoric acid. The amount of fluoride-containing phosphoric acid in the chemical treatment tank 6 is greater than the volume of the inner tank 21 (the maximum amount of fluoride-containing phosphoric acid that the inner tank 21 can store). The circulation pump 26 constantly sends the fluoride-containing phosphoric acid from the upstream end of the circulation pipe 25 to the downstream end of the circulation pipe 25. Therefore, the fluoride-containing phosphoric acid continues to overflow from the inner tank 21 to the outer tank 22 and circulates through the circulation path. The fluoride-containing phosphoric acid is heated by the heater 27 while circulating through the circulation path, and is maintained at a constant temperature higher than room temperature.

[0108] The circulation heating system includes a drain pipe 30 that guides the fluoride-containing phosphoric acid discharged from the circulation pipe 25, and a drain valve 31 that switches between an open state in which the fluoride-containing phosphoric acid is discharged from the circulation pipe 25 to the drain pipe 30 and a closed state in which the fluoride-containing phosphoric acid is not discharged from the circulation pipe 25 to the drain pipe 30. The drain pipe 30 is connected to the circulation pipe 25 downstream of the circulation pump 26. When the drain valve 31 is opened, the fluoride-containing phosphoric acid in the circulation pipe 25 flows into the drain pipe 30 and is discharged from the circulation pipe 25.

[0109] The substrate processing apparatus 1 includes a supply system that supplies fluoride-containing phosphoric acid to the chemical processing tank 6. The supply system includes a pure water pipe 32 that guides pure water from a pure water supply source to the chemical processing tank 6, a phosphoric acid pipe 35 that guides phosphoric acid from a phosphoric acid supply source to the chemical processing tank 6, and a fluoride pipe 38 that guides a fluoride-containing liquid from a fluoride supply source to the chemical processing tank 6. The fluoride-containing liquid is a fluoride liquid or a solution in which fluoride is dissolved. The concentration of fluoride in the fluoride-containing liquid is higher than the concentration of fluoride in the fluoride-containing phosphoric acid.

[0110] The supply system includes a pure water valve 34 attached to the pure water pipe 32, a phosphoric acid valve 37 attached to the phosphoric acid pipe 35, and a fluoride valve 40 attached to the fluoride pipe 38. The phosphoric acid valve 37 switches between an open state in which phosphoric acid in the phosphoric acid pipe 35 is supplied to the chemical treatment tank 6, and a closed state in which phosphoric acid in the phosphoric acid pipe 35 is not supplied to the chemical treatment tank 6. The same applies to the pure water valve 34 and the fluoride valve 40.

[0111] Although not shown, the phosphoric acid valve 37 includes a valve body provided with an internal flow path through which the liquid flows and an annular valve seat forming part of 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 in which the valve element contacts the valve seat and an open position in which the valve element is separated from the valve seat. The same applies to the other valves. The actuator may be a pneumatic actuator or an electric actuator, or may be an actuator other than these. The control device 3 opens and closes the phosphoric acid valve 37 by controlling the actuator.

[0112] When the control device 3 opens the phosphoric acid valve 37, that is, when it switches from a closed state to an open state, the phosphoric acid in the phosphoric acid pipe 35 is supplied to the chemical treatment tank 6. Similarly, when the control device 3 opens the pure water valve 34, the pure water in the pure water pipe 32 is supplied to the chemical treatment tank 6, and when the control device 3 opens the fluoride valve 40, the fluoride-containing liquid in the fluoride pipe 38 is supplied to the chemical treatment tank 6. The phosphoric acid, pure water, and the fluoride-containing liquid are supplied to at least one of the inner tank 21 and the outer tank 22. FIG. 9 shows an example in which phosphoric acid, etc. are supplied to the outer tank 22.

[0113] When pure water or a fluoride-containing liquid is supplied to the chemical treatment tank 6 from the pure water pipe 32 or the fluoride pipe 38, the phosphoric acid concentration in the fluoride-containing phosphoric acid decreases according to the amount of the pure water or the fluoride-containing liquid supplied. When phosphoric acid is supplied to the chemical treatment tank 6 from the phosphoric acid pipe 35, the phosphoric acid concentration in the fluoride-containing phosphoric acid increases according to the amount of phosphoric acid supplied.

[0114] Similarly, when phosphoric acid or pure water is supplied to the chemical treatment tank 6 from the phosphoric acid pipe 35 or the pure water pipe 32, the fluoride concentration in the fluoride-containing phosphoric acid decreases according to the amount of phosphoric acid or pure water supplied. When a fluoride-containing liquid is supplied to the chemical treatment tank 6 from the fluoride pipe 38, the fluoride concentration in the fluoride-containing phosphoric acid increases according to the amount of the fluoride-containing liquid supplied.

[0115] The control device 3 is electrically connected to a pure water flowmeter 33 that measures the flow rate of pure water supplied from the pure water pipe 32 to the chemical treatment tank 6. Similarly, the control device 3 is electrically connected to a phosphoric acid flowmeter 36 that measures the flow rate of phosphoric acid supplied from the phosphoric acid pipe 35 to the chemical treatment tank 6, and is electrically connected to a fluoride flowmeter 39 that measures the flow rate of the fluoride-containing liquid supplied from the fluoride pipe 38 to the chemical treatment tank 6.

[0116] The control device 3 detects the amount of pure water supplied to the chemical treatment tank 6 based on the measurement value of the pure water flow meter 33. Similarly, the control device 3 detects the amount of phosphoric acid supplied to the chemical treatment tank 6 based on the measurement value of the phosphoric acid flow meter 36, and detects the amount of fluoride-containing liquid supplied to the chemical treatment tank 6 based on the measurement value of the fluoride flow meter 39. The concentration of phosphoric acid in the fluoride-containing phosphoric acid and the concentration of fluoride in the fluoride-containing phosphoric acid change depending on the amount and type of liquid supplied to the chemical treatment tank 6.

[0117] The control device 3 is electrically connected to a phosphoric acid concentration meter C1 that measures the concentration of phosphoric acid in fluoride-containing phosphoric acid, and a fluoride concentration meter C2 that measures the concentration of fluoride in fluoride-containing phosphoric acid. The control device 3 is further electrically connected to a thermometer T1 that detects the temperature of fluoride-containing phosphoric acid. FIG. 9 shows an example in which the phosphoric acid concentration meter C1 and the fluoride concentration meter C2 measure the concentration of fluoride-containing phosphoric acid in the inner tank 21, and the thermometer T1 measures the temperature of fluoride-containing phosphoric acid in the inner tank 21. The phosphoric acid concentration meter C1 may measure the concentration of fluoride-containing phosphoric acid in the outer tank 22, or may measure the concentration of fluoride-containing phosphoric acid in the circulation pipe 25. The same applies to the fluoride concentration meter C2 and the thermometer T1.

[0118] The control device 3 detects the concentration of phosphoric acid in the fluoride-containing phosphoric acid based on the measurement value of the phosphoric acid concentration meter C1. When the detected concentration of phosphoric acid is different from the set phosphoric acid concentration, the control device 3 supplies at least one of phosphoric acid, pure water, and a fluoride-containing liquid to the chemical solution treatment tank 6, and makes the concentration of phosphoric acid in the fluoride-containing phosphoric acid approach the set phosphoric acid concentration. This makes it possible to maintain the concentration of phosphoric acid in the fluoride-containing phosphoric acid at the set phosphoric acid concentration.

[0119] Similarly, the control device 3 detects the fluoride concentration in the fluoride-containing phosphoric acid based on the measurement value of the fluoride concentration meter C2. If the detected fluoride concentration is different from the set fluoride concentration, the control device 3 supplies at least one of phosphoric acid, pure water, and a fluoride-containing liquid to the chemical solution treatment tank 6 to make the fluoride concentration in the fluoride-containing phosphoric acid approach the set fluoride concentration. This makes it possible to maintain the fluoride concentration in the fluoride-containing phosphoric acid at the set fluoride concentration.

[0120] The control device 3 also detects the temperature of the fluoride-containing phosphoric acid based on the measurement value of the thermometer T1. If the detected temperature of the fluoride-containing phosphoric acid is higher than the etching temperature, the control device 3 decreases the temperature of the heater 27. If the detected temperature of the fluoride-containing phosphoric acid is lower than the etching temperature, the control device 3 increases the temperature of the heater 27. This allows the temperature of the fluoride-containing phosphoric acid to be increased or decreased and maintained at the etching temperature.

[0121] "Set phosphoric acid concentration" refers to a set value of phosphoric acid concentration in fluoride-containing phosphoric acid to be supplied to the substrate W. "Set fluoride concentration" refers to a set value of fluoride concentration in fluoride-containing phosphoric acid to be supplied to the substrate W. "Etching temperature" refers to a set value of temperature of fluoride-containing phosphoric acid to be supplied to the substrate W. The set phosphoric acid concentration, set fluoride concentration, and etching temperature may be input directly or indirectly by a user to the substrate processing apparatus 1, or may be stored in the control device 3.

[0122] When the phosphoric acid set concentration, the fluoride set concentration, and the etching temperature are stored in the control device 3, the phosphoric acid set concentration, etc. may be specified by a recipe stored in the control device 3. The recipe is information that specifies the processing content, processing conditions, and processing procedure of the substrate W. The control device 3 stores a plurality of recipes. The plurality of recipes differ from each other 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.

[0123] The phosphoric acid set concentration, the fluoride set concentration, and the etching temperature are set so that the etching rate of the silicon oxide film O1 and the etching rate of the silicon nitride film N1 are equal or nearly equal. In other words, the phosphoric acid set concentration, the fluoride set concentration, and the etching temperature are set so that the selectivity ratio is 1 or nearly 1. Therefore, the silicon oxide film O1 and the silicon nitride film N1 that come into contact with the fluoride-containing phosphoric acid in the chemical treatment tank 6 are etched at equal or nearly equal etching rates.

[0124] 4 to 7, the selectivity decreases as the concentration of fluoride in the fluoride-containing phosphoric acid increases, and increases or decreases as the temperature of the fluoride-containing phosphoric acid moves away from the isokinetic temperature (the temperature at which the etching rate of a silicon oxide film is equal to the etching rate of a silicon nitride film). The set phosphoric acid concentration, set fluoride concentration, and etching temperature may be set so that the selectivity is intentionally set to a value different from 1.

[0125] FIG. 10 is a schematic view showing another example of the vertical cross section of the chemical solution treatment tank 6. As shown in FIG.

[0126] The main difference between the chemical treatment tank 6 shown in FIG. 10 and the chemical treatment tank 6 shown in FIG. 9 is that a mixing tank 41 for mixing phosphoric acid, pure water, and a fluoride-containing liquid is provided.

[0127] The supply system for supplying fluoride-containing phosphoric acid to the chemical treatment tank 6 includes a mixing tank 41 for storing fluoride-containing phosphoric acid to be supplied to the chemical treatment tank 6, a supply pipe 42 for guiding the fluoride-containing phosphoric acid from the mixing tank 41 to the chemical treatment tank 6, and a supply pump 43 for sending the fluoride-containing phosphoric acid from the mixing tank 41 to the chemical treatment tank 6 through the supply pipe 42. The supply system further includes a recovery pipe 44 for guiding the fluoride-containing phosphoric acid from the chemical treatment tank 6 to the mixing tank 41, and a recovery valve 45 that switches between an open state in which the fluoride-containing phosphoric acid flows from the recovery pipe 44 to the mixing tank 41 and a closed state in which the fluoride-containing phosphoric acid does not flow from the recovery pipe 44 to the mixing tank 41.

[0128] The supply pipe 42 guides the fluoride-containing phosphoric acid from the mixing tank 41 to the inner tank 21, and the recovery pipe 44 guides the fluoride-containing phosphoric acid from the outer tank 22 to the mixing tank 41. The chemical nozzle 29 discharges the fluoride-containing phosphoric acid guided by the supply pipe 42 toward the inner tank 21. The chemical nozzle 29 may discharge the fluoride-containing phosphoric acid toward both the inner tank 21 and the outer tank 22. The mixing tank 41, the supply pipe 42, the chemical nozzle 29, the inner tank 21, the outer tank 22, and the recovery pipe 44 form a circulation path for circulating the fluoride-containing phosphoric acid. The supply pump 43 constantly sends the fluoride-containing phosphoric acid from the upstream end of the supply pipe 42 to the downstream end of the supply pipe 42.

[0129] The upstream end and downstream end of the circulation pipe 25 are connected to the mixing tank 41, not to the inner tank 21 and the outer tank 22. The mixing tank 41 and the circulation pipe 25 form a circulation path independent of the chemical treatment tank 6, that is, not passing through the chemical treatment tank 6. The phosphoric acid pipe 35, the pure water pipe 32, and the fluoride pipe 38 are connected to the mixing tank 41. The phosphoric acid, the pure water, and the fluoride-containing liquid supplied to the mixing tank 41 from the phosphoric acid pipe 35, the pure water pipe 32, and the fluoride pipe 38 are mixed in the mixing tank 41, and are supplied to the chemical treatment tank 6 via the supply pipe 42 and the chemical nozzle 29. The phosphoric acid concentration meter C1, the fluoride concentration meter C2, and the thermometer T1 measure the concentration or temperature of the fluoride-containing phosphoric acid in the mixing tank 41.

[0130] The control device 3 maintains the concentration of phosphoric acid in the fluoride-containing phosphoric acid in the mixing tank 41 at the set phosphoric acid concentration, and maintains the concentration of fluoride in the fluoride-containing phosphoric acid in the mixing tank 41 at the set fluoride concentration. The control device 3 further maintains the temperature of the fluoride-containing phosphoric acid in the mixing tank 41 at the etching temperature. This makes it possible to supply fluoride-containing phosphoric acid, whose concentration of phosphoric acid, concentration of fluoride, and temperature of the fluoride-containing phosphoric acid are equal or almost equal to the set phosphoric acid concentration, set fluoride concentration, and etching temperature, from the mixing tank 41 to the chemical solution treatment tank 6, and the multiple substrates W in the inner tank 21 can be etched with this fluoride-containing phosphoric acid.

[0131] Next, the single-wafer type substrate processing apparatus 1 will be described.

[0132] Fig. 11A is a schematic plan view showing a layout of a single-wafer type substrate processing apparatus 1 according to one embodiment of the present invention, and Fig. 11B is a schematic side view of the single-wafer type substrate processing apparatus 1.

[0133] 11A, the substrate processing apparatus 1 is a single-wafer type 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 substrate W transferred from the carrier C on the load port LP, a transfer system that transfers the substrate W between the carrier C on the load port LP and the plurality of processing units 2, and a control device 3 that controls the substrate processing apparatus 1.

[0134] The transport system includes an indexer robot IR that loads and unloads the substrate W into and from the carrier C on the load port LP, and a center robot CR that loads and unloads the substrate W into and from each of the processing units 2. The indexer robot IR transports the substrate W between the load port LP and the center robot CR, and the center robot CR transports the substrate 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.

[0135] The multiple processing units 2 form multiple towers TW arranged around a center robot CR in a plan view. Fig. 11A 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. 11B, each tower TW is made up of multiple (e.g., three) processing units 2 stacked one on top of the other.

[0136] FIG. 12 is a schematic diagram showing the inside of the processing unit 2 as viewed horizontally.

[0137] The processing unit 2 includes a box-shaped chamber 52 having an internal space, a spin chuck 57 (substrate holder) that holds a single substrate W horizontally within the chamber 52 while rotating it about a vertical rotation axis A1 passing through the center of the substrate W, a plurality of nozzles that eject processing fluids such as processing liquid and processing gas toward the substrate W held on the spin chuck 57, and a cylindrical processing cup 63 that collects processing liquid that has splashed outward from the spin chuck 57 and the substrate W.

[0138] The chamber 52 includes a box-shaped partition 53 provided with an inlet / outlet 53b through which the substrate W transported by the center robot CR (see FIG. 11A) passes, and a shutter 54 for opening and closing the inlet / outlet 53b. An FFU 51 (fan filter unit 51) for sending clean air (air filtered by a filter) into the chamber 52 is disposed above an air outlet 53a opening in the ceiling surface of the partition 53. The air outlet 53a is provided at the upper end of the chamber 52, and an exhaust duct 56 for discharging gas from within the chamber 52 is disposed at the lower end of the chamber 52.

[0139] The chamber 52 includes a straightening plate 55 that divides the internal space of the chamber 52 into an upper space Su and a lower space SL. The upper space Su between the ceiling surface of the partition wall 53 and the upper surface of the straightening plate 55 is a diffusion space in which clean air diffuses. The lower space SL between the lower surface of the straightening plate 55 and the floor surface of the partition wall 53 is a processing space in which the processing of the substrate W is performed. The spin chuck 57 is disposed in the lower space SL. The processing of the substrate W is performed in a state in which a downward flow of clean air is formed in the lower space SL.

[0140] The spin chuck 57 includes a plurality of chuck pins 58 that horizontally clamp the substrate W, and a disk-shaped spin base 59 that supports the plurality of chuck pins 58. The spin chuck 57 further includes a spin shaft 60 that extends downward from the center of the spin base 59, an electric motor 61 that rotates the plurality of chuck pins 58 and the spin base 59 by rotating the spin shaft 60, and a chuck housing 62 that surrounds the electric motor 61. The spin chuck 57 may be another type of chuck, such as a vacuum chuck.

[0141] The processing cup 63 includes a plurality of guards 64 that receive the processing liquid splashed outward from the spin chuck 57 and the substrate W, and a plurality of cups 65 that receive the processing liquid guided downward by the plurality of guards 64. Figure 12 shows an example in which two guards 64 and two cups 65 are provided, and the outermost cup 65 is integrated with the second guard 64 from the outside.

[0142] The multiple guards 64 are connected to a guard lifting unit 66 that raises and lowers the multiple guards 64 individually in the vertical direction. The guard lifting unit 66 positions the guards 64 at any position within a range from the upper position to the lower position. FIG. 12 shows a state in which the two guards 64 are disposed at the lower position. The upper position is a position where the upper end of the guard 64 is disposed above the holding position of the substrate W by the spin chuck 57. The lower position is a position where the upper end of the guard 64 is disposed below the holding position of the substrate W by the spin chuck 57. The holding position of the substrate W by the spin chuck 57 is a position where the substrate W held by the spin chuck 57 is disposed.

[0143] When the processing liquid is supplied to the rotating substrate W, the controller 3 controls the guard lifting unit 66 to position at least one guard 64 in the upper position. When the processing liquid is supplied to the substrate W in this state, the processing liquid is thrown outward from the substrate W. The thrown-off processing liquid collides with the inner peripheral surface of the guard 64 horizontally facing the substrate W, and is guided to the cup 65 corresponding to this guard 64. As a result, the processing liquid discharged from the substrate W is collected in the cup 65.

[0144] The multiple nozzles include a heating fluid nozzle 67 that sprays a heating liquid toward the upper surface of the substrate W held on the spin chuck 57, a chemical liquid nozzle 71 that sprays fluoride-containing phosphoric acid toward the upper surface of the substrate W held on the spin chuck 57, and a rinsing liquid nozzle 75 that sprays a rinsing liquid toward the upper surface of the substrate W held on the spin chuck 57.

[0145] The chemical liquid nozzle 71 may be a scan nozzle that can move the collision position of the chemical liquid with respect to the substrate W within the upper surface of the substrate W, or may be a fixed nozzle that cannot move the collision position of the chemical liquid with respect to the substrate W. The same applies to the other nozzles. Fig. 12 shows an example in which the chemical liquid nozzle 71 and the heating fluid nozzle 67 are scan nozzles and the rinsing liquid nozzle 75 is a fixed nozzle.

[0146] 12, the heating fluid nozzle 67 is connected to a nozzle moving unit 70, and the chemical nozzle 71 is connected to a nozzle moving unit 74. The nozzle moving unit 74 moves the chemical nozzle 71 horizontally between a processing position where the chemical discharged from the chemical nozzle 71 collides with the upper surface of the substrate W and a standby position where the chemical nozzle 71 is positioned around the spin chuck 57 in a plan view. The same applies to the nozzle moving unit 70.

[0147] The heating fluid nozzle 67 is connected to a heating fluid pipe 68 that guides phosphoric acid, which is an example of a heating fluid, from a heating fluid supply source to the heating fluid nozzle 67. When the control device 3 opens a heating fluid valve 69 attached to the heating fluid pipe 68, the heating fluid nozzle 67 discharges high-temperature (e.g., 100 to 150°C) phosphoric acid, and when the control device 3 closes the heating fluid valve 69, the heating fluid nozzle 67 stops discharging phosphoric acid. The heating fluid may be a heating liquid other than phosphoric acid, or may be a heating gas such as nitrogen gas.

[0148] The chemical nozzle 71 is connected to a chemical pipe 72 that guides fluoride-containing phosphoric acid, which is an example of a chemical liquid, from a chemical supply source to the chemical nozzle 71. When the control device 3 opens a chemical valve 73 attached to the chemical pipe 72, the chemical nozzle 71 discharges high-temperature (e.g., 100 to 150°C) fluoride-containing phosphoric acid, and when the control device 3 closes the chemical valve 73, the chemical nozzle 71 stops discharging the fluoride-containing phosphoric acid.

[0149] The fluoride-containing phosphoric acid supplied to the chemical nozzle 71 is, for example, fluoride-containing phosphoric acid in the mixing tank 41 shown in Fig. 10. This allows fluoride-containing phosphoric acid, the concentration of which is equal to or approximately equal to the set phosphoric acid concentration, set fluoride concentration, and etching temperature, to be discharged from the chemical nozzle 71 and supplied to the substrate W held on the spin chuck 57.

[0150] When the fluoride-containing phosphoric acid in the mixing tank 41 shown in Fig. 10 is supplied to the chemical nozzle 71, the chemical pipe 72 may be directly connected to the mixing tank 41 or may be connected to the mixing tank 41 via the circulation pipe 25. In the former case, the supply pipe 42 shown in Fig. 10 may be used as the chemical pipe 72. More specifically, the chemical nozzle 71 and the chemical valve 73 may be attached to the supply pipe 42 as the chemical pipe 72. The fluoride-containing phosphoric acid collected in the cup 65 may be recovered in the mixing tank 41 via the recovery pipe 44.

[0151] The rinse liquid nozzle 75 is connected to a rinse liquid pipe 76 that guides pure water, which is an example of a rinse liquid, from a rinse liquid supply source to the rinse liquid nozzle 75. When the control device 3 opens a rinse liquid valve 77 attached to the rinse liquid pipe 76, the rinse liquid nozzle 75 discharges the rinse liquid, and when the control device 3 closes the rinse liquid valve 77, the rinse liquid nozzle 75 stops discharging the rinse liquid. The rinse liquid discharged from the rinse liquid nozzle 75 may be at room temperature, or may be higher or lower than room temperature.

[0152] A substrate W having an exposed silicon oxide film O1 and silicon nitride film N1 as shown in Fig. 1F is transported to the substrate processing apparatus 1. The transport system transports one substrate W from a carrier C on the load port LP to the processing unit 2. After the transported substrate W is processed in the processing unit 2, the transport system transports the processed substrate W from the processing unit 2 to the carrier C on the load port LP. Therefore, the substrate W transported into the substrate processing apparatus 1 through the load port LP is processed in the processing unit 2, and then transported out of the substrate processing apparatus 1 through the load port LP.

[0153] After one substrate W is transported to the spin chuck 57 by the center robot CR, the control device 3 causes the spin chuck 57 to hold and rotate the substrate W. In this state, the control device 3 causes the heating fluid nozzle 67, the chemical nozzle 71, and the rinsing liquid nozzle 75 to sequentially discharge phosphoric acid, fluoride-containing phosphoric acid, and pure water in this order. As a result, phosphoric acid, fluoride-containing phosphoric acid, and pure water are sequentially supplied to the entire upper surface of the substrate W in this order. Thereafter, the control device 3 rotates the spin chuck 57 at high speed to dry the substrate W. After the substrate W is dried, the control device 3 stops the rotation of the spin chuck 57 and causes the spin chuck 57 to release the substrate W from its holding. Thereafter, the control device 3 causes the processed substrate W on the spin chuck 57 to be transported to the center robot CR.

[0154] As described above, in this embodiment, the silicon oxide film O1 and the silicon nitride film N1 formed on the substrate W are etched with the fluoride-containing phosphoric acid, which is phosphoric acid containing fluoride, by contacting the silicon oxide film O1 and the silicon nitride film N1 formed on the substrate W. The fluoride-containing phosphoric acid is maintained at an etching temperature that is equal to or close to the isokinetic temperature at which the etching rates of the silicon oxide film O1 and the silicon nitride film N1 are equal to each other at the fluoride concentration in the fluoride-containing phosphoric acid. Therefore, the silicon oxide film O1 and the silicon nitride film N1 can be etched at equal or nearly equal etching rates.

[0155] In this embodiment, fluoride-containing phosphoric acid, which contains fluoride and has an etching temperature that increases the etching rate of the silicon oxide film O1 and the etching rate of the silicon nitride film N1, is brought into contact with the silicon oxide film O1 and the silicon nitride film N1 formed on the substrate W. This allows the silicon oxide film O1 to be etched at a higher etching rate than when the silicon oxide film O1 is etched with phosphoric acid that does not contain fluoride, and allows the silicon nitride film N1 to be etched at a higher etching rate than when the silicon nitride film N1 is etched with phosphoric acid that does not contain fluoride. As a result, the processing time of the substrate W can be shortened, and energy consumption such as power can be reduced.

[0156] In this embodiment, the fluoride-containing phosphoric acid, whose selectivity changes with temperature, is maintained at or near a constant temperature, and the fluoride-containing phosphoric acid at this temperature is brought into contact with the silicon oxide film O1 and the silicon nitride film N1 formed on the substrate W. When the concentration of fluoride in the fluoride-containing phosphoric acid is constant, the selectivity is not constant regardless of the temperature of the fluoride-containing phosphoric acid, but increases or decreases depending on the temperature of the fluoride-containing phosphoric acid. Therefore, by controlling the temperature of the fluoride-containing phosphoric acid, the silicon oxide film O1 and the silicon nitride film N1 can be etched so that the selectivity is 1 or near it, or the silicon oxide film O1 and the silicon nitride film N1 can be etched so that the selectivity is greater than or less than 1.

[0157] In this embodiment, fluoride-containing phosphoric acid containing ammonium fluoride or ammonium hydrogen difluoride at an etching temperature is brought into contact with the silicon oxide film O1 and silicon nitride film N1 formed on the substrate W. This allows the silicon oxide film O1 and silicon nitride film N1 to be etched at equal or approximately equal etching rates. If the fluoride is an alkali metal fluoride such as sodium fluoride (NaF) or potassium fluoride (KF), the substrate W may be contaminated with metal. If the fluoride is ammonium fluoride or ammonium hydrogen difluoride, there is no such risk. Therefore, the silicon oxide film O1 and silicon nitride film N1 can be etched as described above while preventing a decrease in the cleanliness of the substrate W.

[0158] In this embodiment, the temperature of the fluoride-containing phosphoric acid is adjusted so that the selectivity (etching rate of the silicon nitride film N1 / etching rate of the silicon oxide film O1) is within a range of 0.9 to 1.1, and the fluoride-containing phosphoric acid at this temperature is brought into contact with the silicon oxide film O1 and the silicon nitride film N1 formed on the substrate W. The silicon oxide film O1 and the silicon nitride film N1 are etched at a selectivity within a range of 0.9 to 1.1. This makes it possible to prevent the silicon oxide film O1 from being hardly etched, as occurs when the silicon oxide film O1 and the silicon nitride film N1 are etched with phosphoric acid not containing fluoride, while the silicon nitride film N1 is etched at a rate higher than the etching rate of the silicon oxide film O1.

[0159] In this embodiment, fluoride-containing phosphoric acid at an etching temperature is supplied into the memory hole 104 that penetrates the silicon oxide films O1 and the silicon nitride films N1 in the thickness direction Dt of the substrate W. The fluoride-containing phosphoric acid comes into contact with the silicon oxide films O1 and the silicon nitride films N1 that constitute the inner peripheral surface 105 of the memory hole 104, and etches them. If the vertical cross section of the inner peripheral surface 105 of the memory hole 104 before etching (a cross section cut by a plane that is parallel to the thickness direction Dt of the substrate W and includes the center line of the memory hole 104) is linear, etching the inner peripheral surface 105 of the memory hole 104 with phosphoric acid that does not contain fluoride may cause the vertical cross section of the inner peripheral surface 105 of the memory hole 104 to change to a wavy line. If fluoride-containing phosphoric acid at an etching temperature is supplied into the memory hole 104, such a change can be prevented or mitigated.

[0160] In this embodiment, before supplying fluoride-containing phosphoric acid at the etching temperature into memory hole 104, whose diameter changes depending on the position in the thickness direction Dt of substrate W, the entire range of a portion of inner circumferential surface 105 of memory hole 104 in the thickness direction Dt of substrate W is covered with a protective material such as protective film 115, and then fluoride-containing phosphoric acid at the etching temperature is brought into contact with the remaining part of inner circumferential surface 105 of memory hole 104 that is not covered with the protective material. This makes it possible to selectively etch the remaining part of inner circumferential surface 105 of memory hole 104, and intentionally change the shape of memory hole 104.

[0161] In this embodiment, the substrate W is heated and maintained at a constant temperature before being brought into contact with the fluoride-containing phosphoric acid maintained at the etching temperature by heating. This allows the silicon oxide film O1 and the silicon nitride film N1 to be etched in a short time compared to the case where fluoride-containing phosphoric acid at the etching temperature is supplied to the substrate W at room temperature. Furthermore, since the temperature of the substrate W before being brought into contact with the fluoride-containing phosphoric acid is stabilized, when multiple substrates W are successively brought into contact with the fluoride-containing phosphoric acid at the etching temperature, the etching amount between the multiple substrates W can be stabilized.

[0162] Other embodiments The cross section of the memory hole 104, that is, the cross section of the memory hole 104 along a plane perpendicular to the thickness direction Dt of the substrate W, is not limited to a circle, and may be a shape other than a circle, such as an ellipse or a polygon.

[0163] The diameter of memory hole 104 may decrease stepwise, rather than continuously, as it approaches the bottom of memory hole 104. Inner surface 105 of memory hole 104 may include a portion where the diameter of memory hole 104 decreases continuously as it approaches the bottom of memory hole 104, and a portion where the diameter of memory hole 104 decreases stepwise as it approaches the bottom of memory hole 104.

[0164] The diameter of the memory hole 104 may increase continuously or stepwise from the outermost surface 103 of the substrate W to the bottom of the memory hole 104. The inner circumferential surface 105 of the memory hole 104 may include a portion where the diameter of the memory hole 104 increases continuously as it approaches the bottom of the memory hole 104, and a portion where the diameter of the memory hole 104 increases stepwise as it approaches the bottom of the memory hole 104.

[0165] The inner surface 105 of the memory hole 104 may include a portion where the diameter of the memory hole 104 decreases continuously or in steps as it approaches the bottom of the memory hole 104, and a portion where the diameter of the memory hole 104 increases continuously or in steps as it approaches the bottom of the memory hole 104.

[0166] When the inner circumferential surface of a hole such as memory hole 104 is etched with an etching solution, the etching solution becomes more difficult to replace as one approaches the bottom of memory hole 104, so the etching rate tends to decrease as one approaches the bottom of memory hole 104. If the diameter of memory hole 104 increases as one approaches the bottom of memory hole 104, the variation in the diameter of memory hole 104 can be reduced by etching inner circumferential surface 105 of memory hole 104 with fluoride-containing phosphoric acid. In this case, there is no need to protect inlet portion 105e of inner circumferential surface 105 of memory hole 104 from fluoride-containing phosphoric acid with protective film 115, so there is no need to supply filling liquid 111 and protective liquid 114 described above to substrate W.

[0167] The structure of the substrate W to which the fluoride-containing phosphoric acid at the etching temperature is supplied is not limited to the structure shown in Fig. 1A etc. The surface to be etched with the fluoride-containing phosphoric acid may be the inner peripheral surface of a hole other than the memory hole 104, or the side surface of a groove penetrating in the thickness direction Dt of the substrate W a plurality of silicon oxide films O1 and a plurality of silicon nitride films N1 stacked in the thickness direction Dt of the substrate W such that the silicon oxide films O1 and the silicon nitride films N1 are alternately arranged. The surface to be etched with the fluoride-containing phosphoric acid may be a plane perpendicular to the thickness direction Dt of the substrate W.

[0168] Instead of or in addition to heating the substrate W by contacting the heating liquid with the substrate W, the substrate W may be heated before being etched with fluoride-containing phosphoric acid by contacting a heating gas at a temperature higher than room temperature (for example, a temperature in the range of 100 to 150° C.) with the substrate W. The heating gas may be an inert gas such as nitrogen gas, clean air (air filtered by a filter), or other gases.

[0169] Instead of or in addition to contacting the substrate W with a heating fluid such as a heating liquid or a heating gas that is higher than room temperature, the substrate W may be heated by a heater that generates heat when supplied with electric power before being etched with fluoride-containing phosphoric acid. For example, such a heater may be disposed above or below the substrate W shown in FIG.

[0170] Heating of the substrate W before etching may be omitted, that is, fluoride-containing phosphoric acid at the etching temperature may be brought into contact with the substrate W at room temperature.

[0171] 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.

[0172] Any two or more of the above mentioned features may be combined. Any two or more of the above mentioned steps may be combined.

[0173] In addition, various design modifications can be made within the scope of the claims. [Explanation of symbols]

[0174] 1: Substrate processing equipment 6: Chemical treatment tank 27: Heater 29: Chemical nozzle 32: Pure water piping 35: Phosphoric acid piping 38: Fluoride piping 41: Mixing tank 67: Heated fluid nozzle 71: Chemical nozzle 75: Rinse liquid nozzle 101: Base material 102: Laminated film 103: Top surface of substrate 104: Memory Hole 105: Inner surface of memory hole 111: Filling liquid 112: Filling substance 112r:Residual filling material 113:Removal liquid 114: Protective liquid 115:Protective film 116: Thin film O1: Silicon oxide film N1: Silicon nitride film W: Substrate

Claims

1. A substrate processing method for processing a substrate, comprising the steps of: the substrate includes a plurality of silicon oxide films and a plurality of silicon nitride films stacked in a thickness direction of the substrate such that the silicon oxide films and the silicon nitride films are alternately arranged, and a hole recessed in the thickness direction from an outermost surface of the substrate and penetrating the plurality of silicon oxide films and the plurality of silicon nitride films in the thickness direction, the diameter of the hole varying depending on a position in the thickness direction of the substrate, a phosphoric acid heating step of heating the fluoride-containing phosphoric acid, which is phosphoric acid containing fluoride, to maintain the fluoride-containing phosphoric acid at an etching temperature that is equal to or close to an isokinetic temperature at which the etching rates of the silicon oxide film and the silicon nitride film are equal to each other at the fluoride concentration in the fluoride-containing phosphoric acid, so that the ratio of the etching rate of the silicon nitride film to the etching rate of the silicon oxide film falls within a range of 0.9 to 1.1; a phosphoric acid supplying step of etching the silicon oxide films and the silicon nitride films with the fluoride-containing phosphoric acid at the etching temperature by contacting the silicon oxide films and the silicon nitride films exposed in the holes; an inner circumferential surface protection step of covering a part of the inner circumferential surface of the hole in the thickness direction of the substrate with a solid, liquid, or semi-solid protective substance that protects the silicon oxide film and the silicon nitride film from the fluoride-containing phosphoric acid; a step of contacting the remaining part of the inner surface of the hole that is not covered with the protective material with the fluoride-containing phosphoric acid at the etching temperature while protecting the partial area from the fluoride-containing phosphoric acid at the etching temperature with the protective material.

2. a phosphoric acid heating step of heating the fluoride-containing phosphoric acid, which is phosphoric acid containing fluoride, to maintain the fluoride-containing phosphoric acid at an etching temperature that is equal to or close to an isokinetic temperature at which the etching rates of the silicon oxide film and the silicon nitride film are equal to each other at the fluoride concentration in the fluoride-containing phosphoric acid, so that the ratio of the etching rate of the silicon nitride film to the etching rate of the silicon oxide film falls within a range of 0.9 to 1.1; a phosphoric acid supplying step of etching the silicon oxide film and the silicon nitride film formed on a substrate with the fluoride-containing phosphoric acid at the etching temperature; a rinsing liquid supplying step of supplying a rinsing liquid to the substrate while the silicon oxide film and the silicon nitride film remain on the substrate, thereby washing away the fluoride-containing phosphoric acid.

3. 3. The substrate processing method according to claim 1, wherein the fluoride is a compound that increases an etching rate of the silicon oxide film and an etching rate of the silicon nitride film.

4. 4. The substrate processing method according to claim 3, wherein, when the concentration of the fluoride in the fluoride-containing phosphoric acid is constant, the etching rate of the silicon oxide film is higher than the etching rate of the silicon nitride film at a temperature lower than the constant rate temperature, and the etching rate of the silicon oxide film is lower than the etching rate of the silicon nitride film at a temperature higher than the constant rate temperature.

5. 3. The substrate processing method according to claim 1, wherein the fluoride is ammonium fluoride or ammonium hydrogen difluoride.

6. 3. The substrate processing method according to claim 1, wherein a selectivity ratio, which represents a ratio of an etching rate of the silicon nitride film etched in the phosphoric acid supplying step to an etching rate of the silicon oxide film etched in the phosphoric acid supplying step, is within a range of 0.9 to 1.

1.

7. 3. The substrate processing method according to claim 1, further comprising a substrate heating step of heating the substrate to maintain the substrate at a constant temperature before the fluoride-containing phosphoric acid at the etching temperature is brought into contact with the silicon oxide film and the silicon nitride film formed on the substrate.

8. a heater for heating fluoride-containing phosphoric acid, which is phosphoric acid containing fluoride, to maintain the fluoride-containing phosphoric acid at an etching temperature that is equal to or close to an isokinetic temperature at which the etching rates of the silicon oxide film and the silicon nitride film are equal to each other at the fluoride concentration in the fluoride-containing phosphoric acid, so that the ratio of the etching rate of the silicon nitride film to the etching rate of the silicon oxide film falls within a range of 0.9 to 1.1; a chemical nozzle that discharges the fluoride-containing phosphoric acid at the etching temperature and etches the silicon oxide film and the silicon nitride film formed on a substrate with the fluoride-containing phosphoric acid by contacting the discharged fluoride-containing phosphoric acid at the etching temperature with the silicon oxide film and the silicon nitride film; a rinse liquid nozzle that supplies a rinse liquid to the substrate while the silicon oxide film and the silicon nitride film remain on the substrate, thereby washing away the fluoride-containing phosphoric acid.

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