Substrate processing method and substrate processing apparatus

Abstract

The substrate processing method and apparatus of the present invention maintain the fluorinated phosphoric acid at a fixed etching temperature by heating it. This etching temperature is consistent with 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 at the concentration of fluoride in the fluorinated phosphoric acid. The method and apparatus etch the silicon oxide film O1 and the silicon nitride film N1 by contacting the fluorinated phosphoric acid at the etching temperature with the silicon oxide film O1 and the silicon nitride film N1 formed on the substrate W.

Description

Technical Field

[0001] The present invention relates to a substrate processing method and apparatus for processing substrates. Substrates include, for example, semiconductor wafers, liquid crystal display devices, organic EL (electroluminescence) display devices, FPD (Flat Panel Display) substrates, optical disk substrates, magnetic disk substrates, magneto-optical disk substrates, photomask substrates, ceramic substrates, and solar cell substrates. Prior Art

[0002] Patent Document 1 discloses that, when 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 greater than 100:1 (silicon nitride 100).

[0003] Patent Document 2 discloses supplying a phosphoric acid aqueous solution to the surface of a silicon wafer where the silicon oxide film and the silicon nitride film are exposed, thereby suppressing the etching of the silicon oxide film while etching the silicon nitride film. [Prior Art Literature] [Patent Document] [Patent Document 1] Japanese Patent Publication No. 2021-530874 [Patent Document 2] Japanese Patent Application Laid-Open No. 2018-182228 Summary of the Invention

[0004] [Problems to be solved by the invention]

[0005] When phosphoric acid is supplied to a substrate such as a semiconductor wafer to etch silicon oxide and silicon nitride, it is generally necessary to etch silicon nitride with a high selectivity, as described in Patent Documents 1 and 2. However, there are also cases where phosphoric acid is required to etch silicon oxide and silicon nitride at equal or substantially equal etching rates. Patent Documents 1 and 2 fail to meet this requirement.

[0006] One embodiment of the present invention provides a substrate processing method and a substrate processing apparatus that can etch silicon oxide and silicon nitride at equal or substantially equal etching rates using phosphoric acid. [Technical means to solve the problem]

[0007] One embodiment of the present invention provides a substrate processing method, comprising: a phosphoric acid heating step, wherein phosphoric acid containing fluoride, i.e., fluoride-containing phosphoric acid, is heated to maintain the fluoride-containing phosphoric acid at an etching temperature that is consistent with or close to the constant-rate temperature at which the etching rates of a silicon oxide film and a silicon nitride film are equal at the concentration of the fluoride in the fluoride-containing phosphoric acid; and a phosphoric acid supplying step, wherein 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, thereby etching the silicon oxide film and the silicon nitride film using the fluoride-containing phosphoric acid.

[0008] According to this method, phosphoric acid containing fluoride, i.e., fluoride-containing phosphoric acid, is brought into contact with a silicon oxide film and a silicon nitride film formed on a substrate, thereby etching the silicon oxide film and the silicon nitride film using the fluoride-containing phosphoric acid. The fluoride-containing phosphoric acid is maintained at an etching temperature that is consistent with or close to the iso-rate temperature at which the etching rates of the silicon oxide film and the silicon nitride film are equal, depending on 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 substantially equal etching rates.

[0009] The constant-rate temperature depends on the fluoride concentration in the fluoride-containing phosphoric acid. In typical substrate processing, the fluoride concentration in the fluoride-containing phosphoric acid remains approximately constant, and therefore the constant-rate temperature remains approximately constant. Consequently, the fluoride-containing phosphoric acid maintains a constant etching temperature.

[0010] Silicon oxide film is a thin film of silicon oxide. Silicon oxide can be a compound whose chemical formula contains only Si (silicon) and O (oxygen), or a compound whose chemical formula also contains elements other than Si and O. A typical example of silicon oxide is SiO2.

[0011] Silicon nitride film is a thin film of silicon nitride. Silicon nitride can be a compound containing Si (silicon) and N (nitrogen) in its chemical formula, or a compound containing elements other than Si and N. Typical examples of silicon nitride are SiN or Si₃N₄. The number of Si contained in the chemical formula of silicon nitride can also be other than 1 and 3. The number of N contained in the chemical formula of silicon nitride can also be other than 1 and 4.

[0012] The etching rate of a silicon oxide film indicates the amount of thickness reduction 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 indicates the ratio of the etching rate of the silicon nitride film to the etching rate of the silicon oxide film (selectivity of silicon nitride film to silicon oxide film = etching rate of silicon nitride film / etching rate of 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 above embodiment, at least one of the following features may be added to the above 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. Preferably, the fluoride is 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, phosphoric acid containing fluoride at an etching temperature suitable for fluoride is brought into contact with a silicon oxide film and a silicon nitride film formed on a substrate. The fluoride increases the etching rate of the silicon oxide film and the etching rate of the silicon nitride film. As a result, the silicon oxide film can be etched at a higher etching rate than when phosphoric acid without fluoride is used, and the silicon nitride film can be etched at a higher etching rate than when phosphoric acid without fluoride is used. As a result, substrate processing time can be shortened, thereby reducing energy consumption such as electricity.

[0016] When the concentration of the fluoride in the fluoride-containing phosphoric acid is constant, the etching rate of the silicon oxide film may be greater 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 may be less than the etching rate of the silicon nitride film at a temperature higher than the constant-rate temperature.

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

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

[0019] According to this method, phosphoric acid containing a fluoride at an etching temperature of ammonium fluoride or ammonium hydrogen difluoride 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 substantially equal etching rates. When the fluoride is an alkali metal fluoride such as sodium fluoride (NaF) or potassium fluoride (KF), there is a concern that the substrate may be contaminated by the metal. However, when the fluoride is ammonium fluoride or ammonium hydrogen difluoride, this concern is eliminated. Therefore, degradation of the substrate cleanliness can be prevented, and the silicon oxide film and the silicon nitride film can be etched as described above.

[0020] The selectivity ratio of the etching rate of the silicon nitride film during the phosphoric acid supply step to the etching rate of the silicon oxide film during the phosphoric acid supply step is within a range of 0.9 to 1.1. This selectivity range is an example of a selectivity range when the etching temperature is equal to or close to the 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 the silicon nitride film / etching rate of the 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 the silicon nitride film formed on the substrate. The silicon oxide film and the silicon nitride film are etched with a selectivity within a range of 0.9 to 1.1. This prevents the silicon oxide film from being substantially etched while the silicon nitride film is etched at a higher rate than the silicon oxide film, as occurs when etching silicon oxide and silicon nitride films with non-fluoride-containing phosphoric acid.

[0022] The substrate includes: a plurality of silicon oxide films and a plurality of silicon nitride films, which are stacked in the thickness direction of the substrate in a manner that the silicon oxide films and the silicon nitride films are alternately stacked; and holes, which are recessed from the outermost surface of the substrate in the thickness direction, penetrating the plurality of silicon oxide films and the plurality of silicon nitride films in the thickness direction; the phosphoric acid supplying step includes the following step, namely, making the fluoride-containing phosphoric acid at the etching temperature contact the plurality of silicon oxide films and the plurality of silicon nitride films exposed in the holes.

[0023] According to this method, fluoride-containing phosphoric acid at an etching temperature is supplied to a hole formed through a plurality of silicon oxide films and a plurality of silicon nitride films in the thickness direction of a substrate. The fluoride-containing phosphoric acid contacts the plurality of silicon oxide films and the plurality of silicon nitride films forming the inner peripheral surface of the hole, thereby etching them. If the longitudinal cross-section of the inner peripheral surface of the hole before etching (a cross-section taken along a plane parallel to the thickness direction of the substrate and including the centerline of the hole) is straight, etching the inner peripheral surface of the hole with fluoride-free phosphoric acid 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 this 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 to a hole whose diameter varies depending on its position in the thickness direction of the substrate. This maintains the longitudinal cross-sectional shape of the inner circumference of the hole while allowing the inner circumference of the hole to be etched using the fluoride-containing phosphoric acid. When etching the inner circumference of the hole using an etching solution, it becomes increasingly difficult to exchange the etching solution as the bottom of the hole is approached, and the etching rate tends to decrease as the bottom of the hole is approached. In cases where the diameter of the hole increases as the bottom of the hole is approached, etching the inner circumference of the hole using fluoride-containing phosphoric acid maintains the longitudinal cross-sectional shape of the inner circumference of the hole and reduces variations in the hole diameter.

[0026] The inner circumferential surface of the hole may be shaped such that the diameter of the hole decreases or increases continuously or in stages as it approaches the bottom of the hole, from the outermost surface of the substrate to the bottom of the hole. Alternatively, the inner circumferential surface of the hole may include at least one of a portion where the diameter of the hole decreases continuously or in stages as it approaches the bottom of the hole, and a portion where the diameter of the hole increases continuously or in stages as it approaches the bottom of the hole.

[0027] The above-mentioned substrate processing method further includes an inner surface protection step, that is, using a solid, liquid or semi-solid protective substance to protect the above-mentioned silicon oxide film and silicon nitride film from damage by the above-mentioned fluoride-containing phosphoric acid to cover a portion of the inner surface of the above-mentioned hole in the above-mentioned thickness direction of the above-mentioned substrate. The above-mentioned phosphoric acid supply step includes the following steps, that is, using the above-mentioned protective substance to protect the above-mentioned portion from damage by the above-mentioned fluoride-containing phosphoric acid at the above-mentioned etching temperature, and allowing the above-mentioned fluoride-containing phosphoric acid at the above-mentioned etching temperature to contact the remaining portion of the inner surface of the above-mentioned hole not covered by the above-mentioned protective substance.

[0028] According to this method, before supplying fluoride-containing phosphoric acid at an etching temperature to a hole whose diameter varies depending on its position in the thickness direction of the substrate, a portion of the inner peripheral surface of the hole in the thickness direction of the substrate is protected with a protective material. Subsequently, the fluoride-containing phosphoric acid at an etching temperature is brought into contact with the remaining portion of the inner peripheral surface of the hole not covered by the protective material. This allows selective etching of the remaining portion of the inner peripheral surface of the hole and allows the shape of the hole to be intentionally changed.

[0029] If the hole diameter decreases as it approaches the bottom of the hole from the outermost surface of the substrate to the bottom of the hole, the unevenness in hole diameter can be reduced by protecting the entrance-side portion of the inner circumference of the hole with a protective substance and etching the bottom portion of the inner circumference of the hole with phosphoric acid containing a fluoride. Conversely, if the hole diameter increases as it approaches the bottom of the hole from the outermost surface of the substrate to the bottom of the hole, the unevenness in hole diameter can be reduced by protecting the bottom portion of the inner circumference of the hole with a protective substance and etching the entrance-side portion of the inner circumference of the hole with phosphoric acid containing a fluoride.

[0030] When supplying fluoride-containing phosphoric acid to a substrate, a portion of the inner circumference of a hole in the substrate's thickness direction is maintained covered with a protective material. The protective material can be solid, liquid, or semi-solid. The protective material can be a cylindrical protective film coaxial with the inner circumference of the hole, or a protective plug that fills the entire inner circumference of the hole. The remaining portion of the inner circumference of the hole not covered by the protective material can be a portion closer to the bottom of the hole than the protective material, or a portion closer to the hole entrance (the outermost surface of the substrate) than the protective material.

[0031] The substrate processing method further includes a substrate heating step, that is, before the fluoride-containing phosphoric acid at the etching temperature contacts the silicon oxide film and the silicon nitride film formed on the substrate, the substrate is heated to maintain the substrate at a constant temperature.

[0032] According to this method, the substrate is heated and maintained at a constant temperature before contacting the substrate with fluoride-containing phosphoric acid, which is maintained at an etching temperature by heating. This allows etching of silicon oxide and silicon nitride films in a shorter time than when fluoride-containing phosphoric acid at an etching temperature is supplied to a room temperature substrate. Furthermore, the temperature of the substrate prior to contact with the fluoride-containing phosphoric acid is stabilized, allowing for consistent etching across multiple substrates when sequentially contacting the fluoride-containing phosphoric acid at an etching temperature.

[0033] Another embodiment of the present invention, for achieving the above-mentioned purpose, provides a substrate processing apparatus comprising: a heater that heats fluoride-containing phosphoric acid to maintain the fluoride-containing phosphoric acid at an etching temperature that is consistent with or close to the constant-rate temperature at which the etching rates of the silicon oxide film and the silicon nitride film are equal, depending on the concentration of the fluoride in the fluoride-containing phosphoric acid; and a chemical solution nozzle that discharges the fluoride-containing phosphoric acid at the etching temperature. The discharged fluoride-containing phosphoric acid at the etching temperature contacts the silicon oxide film and the silicon nitride film formed on the substrate, thereby etching the silicon oxide film and the silicon nitride film with the fluoride-containing phosphoric acid. This apparatus can achieve the same effects as the above-mentioned substrate processing method.

[0034] The above and other objects, features and effects of the present invention will become more apparent from the following description of the embodiments with reference to the accompanying drawings. Simple diagram description

[0035] 1A-1D are cross-sectional views of a substrate for illustrating an example of substrate processing according to the present embodiment. 1E-H are cross-sectional views of a substrate for illustrating an example of substrate processing according to this embodiment. 2 is a cross-sectional view of a substrate showing images of the inner peripheral surface of a memory hole before and after etching using phosphoric acid without fluoride. 3 is a cross-sectional view of a substrate showing images of the inner peripheral surface of a memory hole before and after etching using fluoride-containing phosphoric acid. FIG4 is a line graph showing the relationship between the concentration of fluoride in fluoride-containing phosphoric acid and the etching rates of silicon oxide films and silicon nitride films. FIG5 is a line graph showing the relationship between the concentration of fluoride in fluoride-containing phosphoric acid and the etching rates of silicon oxide films and silicon nitride films. FIG6 is a line graph showing the relationship between the temperature of fluoride-containing phosphoric acid and the etching rates of silicon oxide films and silicon nitride films. FIG. 7 is a line graph showing the relationship between the temperature of fluoride-containing phosphoric acid and the etching rates of silicon oxide films and silicon nitride films. FIG. 8 is a schematic top view showing the layout of a batch-type substrate processing apparatus according to one embodiment of the present invention. FIG9 is a schematic diagram showing an example of a vertical cross section of a chemical liquid treatment tank. FIG10 is a schematic diagram showing another example of a vertical cross section of a chemical solution treatment tank. FIG. 11A is a schematic top view showing the layout of a single-wafer substrate processing apparatus according to one embodiment of the present invention. FIG. 11B is a schematic side view of a single-wafer substrate processing apparatus. FIG12 is a schematic diagram showing the interior of the horizontal observation processing unit. Implementation Method

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

[0037] Figures 1A to 1H show cross-sections of substrate W taken along a plane perpendicular to its surface. The following describes an example in which substrate W processing is part of the manufacturing process for a three-dimensional NAND flash memory device. In the following description, unless otherwise specified, phosphoric acid refers to an aqueous phosphoric acid solution. The concentration of phosphoric acid refers to the concentration of the phosphoric acid compound (H₃PO₄).

[0038] As shown in Figure 1A, a substrate W comprises a base material 101, such as a silicon wafer; a laminated film 102 laminated on the base material 101; and a memory hole 104 recessed from the outermost surface of the laminated film 102, corresponding to the outermost surface 103 of the substrate W, in the thickness direction Dt of the substrate W. The laminated film 102 forms part of the memory cell array of a three-dimensional NAND flash memory. The memory cell array comprises a plurality of memory cells 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, which are laminated in a manner that alternates between thin silicon oxide films O1 and thin silicon nitride films N1 in the thickness direction Dt of the substrate W. 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 portion of the inner circumferential surface 105 of the memory hole 104 is composed of a plurality of inner circumferential surfaces of the silicon oxide film O1 and a plurality of inner circumferential surfaces of the silicon nitride film N1, which are continuous in the thickness direction Dt of the substrate W, with the inner circumferential surfaces of the silicon oxide film O1 and the inner circumferential surfaces of the silicon nitride film N1 alternating. Figure 1A shows an example in which the diameter of the memory hole 104 decreases continuously as it approaches the bottom of the memory hole 104, from the outermost surface 103 of the substrate W to the bottom of the memory hole 104. The cross-section of the memory hole 104, i.e., the cross-section of the memory hole 104 taken along a plane perpendicular to the thickness direction Dt of the substrate W, is circular.

[0041] As shown in FIG1B , in an example of processing a substrate W according to this embodiment, a filling liquid 111 is supplied to a substrate W having memory holes 104 formed therein, and the memory holes 104 are completely filled with the filling liquid 111. Subsequently, as shown in FIG1C , the filling liquid 111 in the memory holes 104 is transformed into a filling material 112, and the memory holes 104 are filled with the filling material 112. FIG1C shows a state in which the entire memory holes 104 are filled with the filling material 112. The filling material 112 can be a solid or a semi-solid containing a liquid.

[0042] The filling liquid 111 changes to a solid or semi-solid state through, for example, precipitation, coagulation, or solidification. Precipitation refers to the transformation of a solute dissolved in a solvent into a solid state by increasing the solute concentration above the saturation concentration through evaporation of the solvent. Solidification refers to the transformation from a liquid phase to a solid phase by lowering the temperature below the freezing point. Solidification refers to the transformation from a liquid phase to a solid phase through a chemical change caused by the application of energy such as heat or light. After the filling liquid 111 is supplied to the substrate W, it changes to a solid or semi-solid state through precipitation, coagulation, or solidification, thereby transforming the filling liquid 111 into the filling material 112.

[0043] The filling liquid 111 may also be a solution containing a solute and a solvent. The solute may be at least one selected from the group consisting of heat-sensitive water-soluble resins, acrylic resins, phenolic resins, epoxy resins, melamine resins, urea resins, unsaturated polyester resins, alkyd resins, polyurethanes, polyimides, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyvinyl acetate, polytetrafluoroethylene, acrylonitrile-butadiene-styrene resins, acrylonitrile-styrene resins, polyamides, polyacetals, polycarbonates, polyvinyl alcohol, modified polyphenylene ethers, polybutylene terephthalate, polyethylene terephthalate, polyphenylene sulfide, polysulfone, polyetheretherketone, and polyamide imides. Heat-sensitive water-soluble resins are resins that are poorly soluble or insoluble in water before being heated to a predetermined deterioration temperature or higher, and become water-soluble upon heating to a temperature above the deterioration temperature. The solvent preferably has a higher volatility than water. PGEE (propylene glycol monoethyl ether) is preferably used as the solvent.

[0044] The filling liquid 111 may also contain a sublimable substance. Sublimable substances include various substances that have a high vapor pressure at 5°C to 35°C and that transition from a solid phase to a gas phase without passing through a liquid phase. Examples of sublimable substances include hexamethylenetetramine, 1,3,5-trioxane, 1-pyrrolidinodisulfonate ammonium, metaldehyde, paraffin wax with approximately 20 to 48 carbon atoms, tert-butyl alcohol, p-dichlorobenzene, naphthalene, L-menthol, and fluorinated hydrocarbon compounds. Fluorinated hydrocarbon compounds are particularly useful as sublimable substances. 1,1,2,2,3,3,4-heptafluorocyclopentane is particularly preferred.

[0045] The solvent may be at least one selected from the group consisting of, for example, pure water (deionized water: DIW (deionized water)), aliphatic hydrocarbons, aromatic hydrocarbons, esters, alcohols, and ethers. Specifically, examples of the solvent include pure water, methanol, ethanol, IPA, butanol, ethylene glycol, propylene glycol, NMP (N-methyl-2-pyrrolidone), DMF (N,N-dimethylformamide), DMA (dimethylacetamide), DMSO (dimethyl sulfoxide), 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-ditrifluorotoluene.

[0046] After forming the filling material 112 within the memory holes 104, as shown in FIG1D , a removal liquid 113 that dissolves the filling material 112 is supplied to the substrate W. This leaves the filling material 112 at the bottom of the memory holes 104, and the removal liquid 113 removes the filling material 112 from the memory holes 104. The removal liquid 113 supplied to the substrate W contacts the filling material 112 within the memory holes 104, dissolving the filling material 112 from the entrance side of the memory holes 104 toward the bottom of the memory holes 104. As a result, the end surface of the filling material 112 moves toward the bottom of the memory holes 104, gradually reducing the height of the filling material 112.

[0047] Removal liquid 113 can be, for example, a diluent, toluene, organic solvents such as acetates, alcohols, and glycols, or acidic liquids such as acetic acid, formic acid, and glycolic acid. It is particularly preferred to use a solvent compatible with the aqueous liquid as removal liquid 113. For example, isopropyl alcohol (IPA) is preferably used as removal liquid 113.

[0048] The filling material 112 is removed from the entrance of the memory hole 104 to the middle of the memory hole 104. After the filling material 112 remains in the area from the middle of the memory hole 104 to the bottom of the memory hole 104, the removal liquid 113 is removed from the substrate W. Removal of the removal liquid 113 can also be performed by replacing the removal 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 can 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 residual filling material 112r. The portion of the inner circumferential surface 105 of the memory hole 104 not in contact with the residual filling material 112r is defined as the entrance-side portion 105e of the inner circumferential surface 105 of the memory hole 104, and the portion of the inner circumferential surface 105 of the memory hole 104 in contact with the residual filling material 112r is defined as the bottom-side portion 105b of the inner circumferential surface 105 of the memory hole 104. At least a portion of the entrance-side portion 105e is formed by the inner circumferential surfaces of the plurality of silicon oxide films O1 and the inner circumferential surfaces of the plurality of silicon nitride films N1. At least a portion of the bottom-side portion 105b is formed by the inner circumferential surfaces of the other circumferential silicon oxide films O1 and the inner circumferential surfaces of the other circumferential silicon nitride films N1.

[0050] After partially removing the filling material 112 from the memory hole 104, a protective liquid 114 is supplied to the substrate W as shown in FIG1E , forming a protective film 115, an example of a protective material, 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 closer to the inlet side of the memory hole 104 than the remaining filling material 112r within the memory hole 104, is filled with the protective liquid 114. The inlet-side portion 105e of the inner circumferential surface 105 of the memory hole 104 and the end surface of the remaining filling material 112r come into contact with the protective liquid 114.

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

[0052] Protective liquid 114 adheres to the plurality of silicon oxide films O1 and the plurality of silicon nitride films N1 that constitute the inlet-side portion 105e of the inner circumferential surface 105 of the memory hole 104, forming a protective film 115 on the inlet-side portion 105e of the inner circumferential surface 105 of the memory hole 104. Protective film 115 is a cylindrical liquid film coaxial with the inner circumferential surface 105 of the memory hole 104, and it extends over the entire inlet-side portion 105e of the inner circumferential surface 105 of the memory hole 104. While a boundary between protective liquid 114 and protective film 115 is shown in FIG1E for ease of understanding, this boundary does not actually exist.

[0053] When the protective liquid 114 contacts 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 liquid 114 is removed from the substrate W. The protective liquid 114 can also 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, it remains on the inlet-side portion 105e of the inner circumferential surface 105 of the memory hole 104.

[0054] After the protective liquid 114 contacts the inlet-side portion 105e of the inner circumferential surface 105 of the memory hole 104, as shown in FIG1F , while the protective film 115 remains on the inlet-side portion 105e of the inner circumferential surface 105 of the memory hole 104, the filler 112 is removed from the bottom area of ​​the memory hole 104, i.e., the area within the memory hole 104 occupied by the remaining filler 112r. Removal of the remaining filler 112r can also be performed by supplying a removal liquid 113 to the substrate W, as shown in FIG1F . In this case, the protective liquid 114 within the memory hole 104 can also be replaced by the removal liquid 113. Removal of the remaining filler 112r can also be performed by heating the substrate W. If the remaining filler 112r contains a sublimable substance, heating the substrate W can also cause the remaining filler 112r to sublime.

[0055] When the remaining filling material 112r is removed from the memory hole 104 as shown in FIG1F , the bottom portion 105b of the inner circumference 105 of the memory hole 104 is exposed from the filling material 112 while the inlet-side portion 105e of the inner circumference 105 of the memory hole 104 is covered by the protective film 115. In this state, as shown in FIG1G , fluoride-containing phosphoric acid is supplied to the substrate W. FIG1G illustrates an example in which the fluoride contained in the fluoride-containing phosphoric acid is ammonium fluoride (NH 4F). The fluoride-containing phosphoric acid supplied to the substrate W enters the memory hole 104 from the inlet and passes through the inner side of the cylindrical protective film 115. As a result, the bottom area of ​​the memory hole 104 and the area inside 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 solution of phosphoric acid containing fluoride). Fluoride-containing phosphoric acid is an example of a chemical solution containing a substance that chemically reacts with a substrate W. Fluoride-containing phosphoric acid is also an example of an etching solution used to etch a substrate W. The fluoride contained in the fluoride-containing phosphoric acid can be a solid fluoride dissolved in phosphoric acid, or it can be a fluoride contained in a fluoride-containing liquid mixed with phosphoric acid (a fluoride liquid or a solution containing a dissolved fluoride).

[0057] The fluoride contained in the fluoride-containing phosphoric acid is ammonium fluoride (NH4F) or ammonium difluoride (NH4HF2). When the fluoride is ammonium fluoride, the fluoride concentration in the fluoride-containing phosphoric acid is 0.15-1.5 wt% (mass percentage concentration). The concentration of the phosphoric acid before adding the fluoride (the concentration of phosphoric acid in the aqueous phosphoric acid solution) is 85%. The concentrations of phosphoric acid and fluoride are not limited to the above.

[0058] The plurality of silicon oxide films O1 and the plurality of silicon nitride films N1 forming the entrance-side portion 105e of the inner circumferential surface 105 of the memory hole 104 are protected from damage by the fluoride-containing phosphoric acid by the protective film 115. In contrast, the plurality of silicon oxide films O1 and the plurality of silicon nitride films N1 forming the bottom-side portion 105b of the inner circumferential surface 105 of the memory hole 104 come into contact with the fluoride-containing phosphoric acid and are etched by it. As described below, the fluoride-containing phosphoric acid is supplied to the substrate W under processing conditions that allow the silicon oxide film O1 and the silicon nitride film N1 to etch at equal or substantially equal rates. Consequently, the bottom-side portion 105b of the inner circumferential surface 105 of the memory hole 104 is etched, while the entrance-side portion 105e of the inner circumferential surface 105 of the memory hole 104 is not etched or is barely etched.

[0059] The bottom portion 105b of the inner circumferential surface 105 of the memory hole 104 is etched at all locations along the circumference of the memory hole 104 and at all locations along the depth direction of the memory hole 104, which coincides with the thickness direction Dt of the substrate W. Therefore, the height of the bottom portion 105b of the inner circumferential 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) remains unchanged or barely changes, but the diameter of the bottom portion 105b of the inner circumferential surface 105 of the memory hole 104 increases at all locations along the thickness direction Dt of the substrate W. The bottom portion 105b of the inner circumferential surface 105 of the memory hole 104 after etching is cylindrical and coaxial with the bottom portion 105b of the inner circumferential surface 105 of the memory hole 104 before etching.

[0060] FIG1A shows an example in which the memory hole 104 tapers toward the bottom of the memory hole 104. In this example, before fluoride-containing phosphoric acid is supplied to the substrate W, the diameter of the memory hole 104 is greatest near the entrance of the memory hole 104 and smallest 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 circumferential surface 105 of the memory hole 104 remains unchanged or barely changes. Meanwhile, the diameter of the bottom-side portion 105b of the inner circumferential surface 105 of the memory hole 104 etched by the silicon oxide film O1 and the silicon nitride film N1 increases. The minimum diameter of the memory hole 104 approaches its maximum diameter. Consequently, the difference between the maximum and minimum diameters of the memory hole 104 decreases.

[0061] After a predetermined time has passed since the start of supplying the fluoride-containing phosphoric acid to the substrate W, the fluoride-containing phosphoric acid is removed from the substrate W. Removal of the fluoride-containing phosphoric acid can also be performed by replacing the fluoride-containing phosphoric acid in contact with the substrate W with a liquid such as a cleaning solution. The protective film 115 is removed after the fluoride-containing phosphoric acid is removed, or while the fluoride-containing phosphoric acid is removed, by heating the substrate W, irradiating the substrate W with ultraviolet light, or the like. The protective film 115 may remain as long as it does not affect the characteristics of the 3D NAND flash memory.

[0062] After the fluoride-containing phosphoric acid is removed from the substrate W, as shown in FIG1H , a thin film 116, which forms part of a three-dimensional NAND flash memory, is deposited over the entire inner circumference 105 of the memory hole 104 by vapor deposition, such as chemical vapor deposition. The thin film 116, which contacts the inner circumference 105 of the memory hole 104, forms part of a plurality of memory cells arranged in the thickness direction Dt of the substrate W. The thin film 116 can be a conductive film such as a polysilicon film or an insulating film such as a silicon oxide film. The silicon nitride film N1 can also be a sacrificial film that is replaced by a thin film such as a metal film after the thin film 116 is deposited on the inner circumference 105 of the memory hole 104.

[0063] The series of steps from forming the memory hole 104 to depositing the thin film 116 on the inner circumferential surface 105 of the memory hole 104 involves a hole shape correction step in which the shape of the memory hole 104 is corrected by wet etching. The hole shape correction step is performed by a wet process in which a processing liquid contacts the substrate W. In contrast, the memory hole 104 is formed by dry etching, an example of a dry process. The thin film 116 in contact with the inner circumferential surface 105 of the memory hole 104 is formed by vapor deposition, an example of a dry process.

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

[0065] Next, the cross-section of the substrate W before and after etching is described.

[0066] FIG2 is a cross-sectional view of a substrate W showing the image of the inner peripheral surface 105 of the memory hole 104 before and after etching with phosphoric acid containing no fluoride (hereinafter simply referred to as "phosphoric acid"). FIG3 is a cross-sectional view of a substrate W showing the image of the inner peripheral surface 105 of the memory hole 104 before and after etching with phosphoric acid containing fluoride.

[0067] In Figures 2 and 3, the inner circumference 105 of the memory hole 104 before etching is represented by a two-dot chain line, and the inner circumference 105 of the memory hole 104 after etching is represented by a solid line. The shapes of the inner circumference 105 of the memory hole 104 before and after etching are merely images and may differ from the actual shape. Figure 3 shows an example in which the fluoride contained in the fluoride-containing phosphoric acid is ammonium fluoride (NH4F).

[0068] At least a portion of the inner circumferential surface 105 of the memory hole 104 is composed of a plurality of inner circumferential surfaces of the silicon oxide film O1 and a plurality of inner circumferential surfaces of the silicon nitride film N1, which are continuous in the thickness direction Dt of the substrate W, with the inner circumferential surfaces of the silicon oxide film O1 and the inner circumferential surfaces of the silicon nitride film N1 alternating. When phosphoric acid is supplied to the memory hole 104, the silicon oxide film O1 is not etched or is hardly etched by the phosphoric acid. On the other hand, the silicon nitride film N1 is etched by the phosphoric acid at a faster rate than the etching rate of the silicon oxide film O1.

[0069] As shown in FIG2 , when the inner circumference 105 of the memory hole 104 is etched with phosphoric acid, the diameter of the memory hole 104 remains unchanged or barely changes at the locations of the plurality of silicon oxide films O1, while increasing at the locations of the plurality of silicon nitride films N1. As shown by the two-dot chain line in FIG2 , while the diameter of the memory hole 104 is uniform before etching, when the inner circumference 105 of the memory hole 104 is etched with phosphoric acid, the longitudinal cross-section of the inner circumference 105 of the memory hole 104 (a cross-section taken along a plane parallel to the thickness direction Dt of the substrate W and including the centerline of the memory hole 104) changes from a straight line to a wavy line. In this case, the inner circumference 105 of the memory hole 104 changes to a cylindrical shape, with the diameter decreasing at the locations of the plurality of silicon oxide films O1 and increasing at the locations of the plurality of silicon nitride films N1.

[0070] A thin film 116, which forms part of a three-dimensional NAND flash memory, is formed on the inner circumference 105 of the memory hole 104 (see FIG. 1H ). The longitudinal cross-section of the inner circumference 105 of the memory hole 104 preferably has minimal undulations. Furthermore, the diameter of the memory hole 104 is preferably as uniform as possible. FIG. 3 shows an example in which the diameter of the memory hole 104 after etching is also uniform, and the longitudinal cross-section of the inner circumference 105 of the memory hole 104 after etching also has minimal undulations. In this example, the longitudinal cross-section of the inner circumference 105 of the memory hole 104 is maintained in a straight line during etching.

[0071] As described below, fluoride-containing phosphoric acid is supplied to the inner peripheral surface 105 of the memory hole 104 under processing conditions that allow the silicon oxide film O1 and the silicon nitride film N1 to etch at equal or substantially equal etching rates. Consequently, not only the silicon nitride film N1 but also the silicon oxide film O1 can be etched at a sufficient etching rate, and the formation of a plurality of annular depressions, which are recessed in the direction Dp of the surface of the substrate W (a direction perpendicular to the thickness direction Dt of the substrate W) at a plurality of locations of the silicon nitride film N1, on the inner peripheral surface 105 of the memory hole 104 can be prevented. Even if such depressions are formed, they can be made shallow.

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

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

[0074] Figures 4 through 7 show the etching rates of silicon oxide and silicon nitride films using a solution consisting of ammonium fluoride added to 85% phosphoric acid (an 85% phosphoric acid aqueous solution). In Figures 4 through 7, the vertical axis represents the etching rate, and the horizontal axis represents the ammonium fluoride concentration or the temperature of the fluoride-containing phosphoric acid. The etching rate indicates the reduction in film thickness per unit time.

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

[0076] Figure 6 is a line graph showing the relationship between the etching rates of silicon oxide and silicon nitride films and the temperature of the fluoride-containing phosphoric acid when the concentration of ammonium fluoride in the fluoride-containing phosphoric acid is 0.15 wt %. Figure 7 is a line graph showing the relationship between the etching rates of silicon oxide and silicon nitride films and the temperature of the fluoride-containing phosphoric acid when the concentration of ammonium fluoride in the fluoride-containing phosphoric acid is 0.3 wt %. The single-dot chain line in Figure 7 shows the predicted change in the etching rate of the silicon oxide film, and the double-dot chain line in Figure 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 is heated at 120°C, the etching rates of silicon oxide and silicon nitride films increase with increasing ammonium fluoride concentration. When the ammonium fluoride concentration is below 0.15 wt%, the difference between the etching rates of silicon oxide and silicon nitride films is smaller than when the concentration exceeds 0.15 wt%. When the ammonium fluoride concentration exceeds 0.15 wt%, the etching rate of silicon oxide is higher than that of silicon nitride, and the difference between the two increases with increasing ammonium fluoride concentration.

[0078] As shown in Figure 5, when the fluoride-containing phosphoric acid is heated at 130°C, the etching rates of silicon oxide and silicon nitride films increase with increasing ammonium fluoride concentration. When the ammonium fluoride concentration is below 0.15 wt%, the etching rate of silicon oxide is lower than that of silicon nitride. When the ammonium fluoride concentration is below 0.3 wt%, the difference between the etching rates of silicon oxide and silicon nitride is smaller than when the concentration exceeds 0.3 wt%. When the ammonium fluoride concentration exceeds 0.3 wt%, the etching rate of silicon oxide is higher than that of silicon nitride, and the difference between the two increases with increasing ammonium fluoride concentration.

[0079] As shown in Figure 6, when the ammonium fluoride concentration is 0.15 wt%, the etching rate of the silicon oxide film remains roughly constant when the temperature of the fluoride-containing phosphoric acid is below 120°C, and decreases as the temperature rises above 120°C. The etching rate of the silicon nitride film remains roughly constant when the temperature of the fluoride-containing phosphoric acid is below 90°C, and increases as the temperature rises above 90°C.

[0080] As shown in Figure 6, when the temperature of the fluoride-containing phosphoric acid is below 120°C, the etching rate of the silicon oxide film is greater than that of the silicon nitride film. When the temperature of the fluoride-containing phosphoric acid exceeds 120°C, the etching rate of the silicon oxide film is less than that of the silicon nitride film. The difference between the etching rates of the silicon oxide film and the silicon nitride film decreases as the temperature of the fluoride-containing phosphoric acid approaches 120°C.

[0081] As shown in Figure 7, when the ammonium fluoride concentration 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 below 120°C, and decreases with increasing temperature when the temperature of the fluoride-containing phosphoric acid is between 120°C and 130°C. The etching rate of the silicon nitride film increases with increasing temperature when the temperature of the fluoride-containing phosphoric acid is between 80°C and 130°C. According to the measurement results shown in Figure 6, when the temperature of the fluoride-containing phosphoric acid exceeds 130°C, the etching rate of the silicon oxide film (see the single-dot chain line in Figure 7) remains approximately constant, while the etching rate of the silicon nitride film (see the double-dot chain line in Figure 7) increases with increasing temperature.

[0082] As shown in Figure 7, when the temperature of the fluoride-containing phosphoric acid is below 130°C, the etching rate of the silicon oxide film is greater than that of the silicon nitride film. When the temperature of the fluoride-containing phosphoric acid exceeds 130°C, the etching rate of the silicon oxide film is predicted 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 decreases as the temperature of the fluoride-containing phosphoric acid approaches 130°C.

[0083] In Figures 6 and 7, the temperature of the fluoride-containing phosphoric acid at which the broken line representing the etching rate of the silicon oxide film intersects the broken line representing the etching rate of the silicon nitride film is defined as the iso-rate 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, an iso-rate temperature is determined. In other words, the iso-rate temperature depends on the concentration of fluoride in the fluoride-containing phosphoric acid, and is referred to as the temperature of the fluoride-containing phosphoric acid at which the etching rate of the silicon oxide film is equal to the etching rate of the silicon nitride film. Conversely, when the concentration of phosphoric acid in the fluoride-containing phosphoric acid and the temperature of the fluoride-containing phosphoric acid are determined, an iso-rate concentration of fluoride is determined. The iso-rate concentration of fluoride is the concentration of fluoride at which the etching rate of the silicon oxide film is equal to the etching rate of the silicon nitride film.

[0084] The results shown in Figures 4 and 5 indicate that the addition of fluoride to phosphoric acid increases the etching rates of silicon oxide and silicon nitride films. Furthermore, the results shown in Figures 4 and 5 indicate that, when the temperature of the fluoride-containing phosphoric acid is constant, the etching rates of silicon oxide and silicon nitride films increase with increasing fluoride concentration. The results shown in Figures 4 and 5 also indicate that, when the fluoride concentration in the fluoride-containing phosphoric acid exceeds a certain value (0.15 wt% in Figure 4 and 0.3 wt% in Figure 5), the etching rate of silicon oxide increases at a greater rate than the etching rate of silicon nitride films as the fluoride concentration in the fluoride-containing phosphoric acid increases.

[0085] The results shown in Figures 6 and 7 show that the etching rate of the silicon oxide film does not change significantly even when the temperature of the fluoride-containing phosphoric acid changes, while the etching rate of the silicon nitride film increases as the temperature of the fluoride-containing phosphoric acid increases. Furthermore, the results shown in Figures 6 and 7 show that if the fluoride concentration in the fluoride-containing phosphoric acid is constant, there exists a constant etching temperature (in Figures 6 and 7, the temperature at the intersection of the broken lines representing the etching rates of the silicon oxide film and the silicon nitride film) at which the etching rates of the silicon oxide film and the silicon nitride film are equal. As shown in Figures 6 and 7, as the fluoride concentration in the fluoride-containing phosphoric acid increases, the constant etching temperature also increases.

[0086] The results shown in Figures 4 to 7 indicate that by maintaining the phosphoric acid concentration and the fluoride concentration in the fluoride-containing phosphoric acid at or near a constant temperature while maintaining the fluoride-containing phosphoric acid at or near a constant temperature, the silicon oxide film and the silicon nitride film can be etched at equal or substantially equal etching rates. Increasing the fluoride concentration in the fluoride-containing phosphoric acid increases the etching rate of the silicon oxide film, and the etching rate of the silicon nitride film corresponding to the constant temperature also increases. Therefore, in addition to the above conditions, by maintaining the fluoride concentration in the fluoride-containing phosphoric acid at as high a value as possible, the silicon oxide film and the silicon nitride film can be etched at equal or substantially equal, high etching rates.

[0087] During the etching of the bottom portion 105b of the inner circumferential surface 105 of the memory hole 104 (see FIG. 1G ), phosphoric acid containing a fluoride is supplied to the substrate W at a constant etching temperature that is consistent with or close to the constant-rate temperature. This allows the silicon oxide film and the silicon nitride film constituting the bottom portion 105b of the inner circumferential surface 105 of the memory hole 104 to be etched at equal or substantially equal, high etching rates. The etching temperature can be set such that the selectivity ratio (etching rate of the silicon nitride film / etching rate of the 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. Alternatively, the selectivity ratio can be set such that at least one of the etching rates of the silicon oxide film and the silicon nitride film is outside the aforementioned range.

[0088] Here, the case of etching silicon oxide film and silicon nitride film using fluoride-containing phosphoric acid including ammonium fluoride is described. However, the fluoride contained in the fluoride-containing phosphoric acid may be a fluoride other than ammonium fluoride such as ammonium bifluoride. When ammonium bifluoride is dissolved in water, such as "NH4HF2 As shown in "NH4F+HF", it decomposes into ammonium fluoride and hydrogen fluoride. Therefore, it is believed that phosphoric acid containing fluoride including ammonium bifluoride has the same characteristics as phosphoric acid containing fluoride including ammonium fluoride.

[0089] Next, a description will be given of a substrate processing apparatus 1 that supplies fluoride-containing phosphoric acid to a substrate 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] FIG8 is a schematic top view showing the 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 device that processes multiple substrates W at once. The apparatus 1 includes a loading port LP that holds a carrier C for receiving disc-shaped substrates W, such as semiconductor wafers; a processing unit 2 that processes the substrates W transferred from the loading port LP using a processing fluid, such as a chemical solution or a cleaning solution; a transport system that transports the substrates W between the loading port LP and the processing unit 2; and a control unit 3 that controls the apparatus 1.

[0092] The control device 3 is a computer comprising a memory that stores information such as programs and a CPU (central processing unit) that controls the substrate processing apparatus 1 according to the programs stored in the memory. The control device 3 controls the substrate processing apparatus 1 to perform the following operations, such as transporting and processing substrates W. In other words, the control device 3 is programmed to perform the following operations, such as transporting and processing substrates W.

[0093] The processing unit 2 includes a plurality of liquid treatment tanks 4, which store treatment liquids for immersing a plurality of substrates W; and a drying tank 8, which dries the plurality of substrates W using a drying method such as reduced pressure drying. Reduced pressure drying is a drying method that evaporates liquid adhering to the substrates W by reducing the air pressure. The plurality of liquid treatment tanks 4 are arranged linearly in the depth direction of the substrate processing apparatus 1 (left-right direction in FIG. 8 ) when viewed from above. The drying tank 8 is positioned between the transport system and the plurality of liquid treatment tanks 4 in the depth direction of the substrate processing apparatus 1 when viewed from above.

[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 a plurality of carriers C; and a posture change robot 10 that loads and unloads a plurality of substrates W from the carriers C held by the carrier transport device 9, changing the posture of the substrates W between a horizontal and vertical posture. The posture change robot 10 performs a batch assembly operation, which forms a batch from a plurality of substrates W removed from the plurality of carriers C; and a batch release operation, which stores the plurality of substrates W contained in a batch back into the plurality of carriers C.

[0095] The transport system further includes a main transport robot 11 that transports a plurality of substrates W between the posture changing robot 10 and the processing unit 2, and a plurality of auxiliary transport robots 12 that transport a plurality of substrates W between the main transport robot 11 and the processing unit 2. FIG8 shows an example in which two auxiliary transport robots 12 and two pairs of liquid processing tanks 4 are provided. The auxiliary transport robots 12 carry a plurality of substrates W into and out of each of the two paired liquid processing tanks 4, and transport a plurality of substrates W between the two paired liquid processing tanks 4.

[0096] The main transfer robot 11 receives a batch of substrates W, comprising a plurality of substrates W (e.g., 50 substrates), from the posture changing robot 10 and delivers the received batch of substrates W to one of the plurality of auxiliary transfer robots 12. The auxiliary transfer robots 12 immerse the batch of substrates W received by the main transfer robot 11 in the processing liquid within at least one liquid processing tank 4. The main transfer robot 11 then receives the batch of substrates W from the auxiliary transfer robot 12 and transfers the received batch of substrates W into the drying tank 8.

[0097] The plurality of liquid processing tanks 4 include a heating tank 5 storing a heating liquid for immersing the plurality of substrates W; a chemical processing tank 6 storing a chemical liquid for immersing the plurality of substrates W; and a cleaning tank 7 storing a cleaning liquid for immersing the plurality of substrates W. The heating tank 5, chemical processing tank 6, and cleaning tank 7 are arranged linearly in the depth direction of the substrate processing apparatus 1 when viewed from above. A drying tank 8 is positioned between the transport system and the cleaning tank 7 in the depth direction of the substrate processing apparatus 1 when viewed from above.

[0098] The heating liquid is phosphoric acid, the chemical solution is fluoride-containing phosphoric acid, and the cleaning liquid is pure water. The heating liquid may also be a liquid other than phosphoric acid, such as pure water. Similarly, the cleaning liquid may also be a liquid other than pure water. For example, the cleaning liquid may be any of IPA (isopropyl alcohol), electrolytic ionized water, hydrogen water, ozone water, hydrochloric acid water at a dilute concentration (e.g., approximately 10-100 ppm), and ammonia water at a dilute concentration (e.g., approximately 10-100 ppm).

[0099] The substrate W with the exposed silicon oxide film O1 and silicon nitride film N1 shown in FIG1F is transported to the substrate processing apparatus 1. The transport system sequentially transports a batch of substrates W to the heating treatment tank 5, the chemical treatment tank 6, the cleaning treatment tank 7, and the drying treatment tank 8. Thus, the substrates W loaded into the substrate processing apparatus 1 via the loading port LP are sequentially exposed to phosphoric acid, fluoride-containing phosphoric acid, and pure water, and dried. By supplying the fluoride-containing phosphoric acid to the substrates W, the bottom portion 105b of the inner circumference 105 of the memory hole 104 is etched, as shown in FIG1G . The fluoride-containing phosphoric acid adhering to the substrates W is rinsed away with pure water. The substrates W wetted with pure water are dried in the drying treatment tank 8. The dried substrates W are unloaded from the substrate processing apparatus 1 via the loading 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 above 100°C. The pure water in the cleaning treatment tank 7 can be at room temperature (constant or approximately constant temperature between 15 and 30°C) or maintained at a constant temperature higher or lower than room temperature. The temperature of the phosphoric acid is, for example, in the range of 100 to 150°C, and the temperature of the fluoride-containing phosphoric acid is, for example, in the range of 100 to 150°C. The temperature of the phosphoric acid can be equal to, higher or lower than, the temperature of the fluoride-containing phosphoric acid. The phosphoric acid in the heat treatment tank 5 heats the substrate W, and thus the substrate W is transferred to the chemical treatment tank 6 at the same or approximately the same temperature as the phosphoric acid in the heat treatment tank 5.

[0101] When the heating liquid is phosphoric acid, the silicon oxide film O1 and the silicon nitride film N1 are slightly etched when the heating liquid contacts them. If this 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 heating liquid piping.

[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 heating treatment tank 5 and the cleaning treatment tank 7 have the same structure as the chemical liquid treatment tank 6.

[0103] The chemical treatment tank 6 includes an inner tank 21 storing fluoride-containing phosphoric acid and an outer tank 22 storing fluoride-containing phosphoric acid that overflows 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 within the inner tank 21. The fluoride-containing phosphoric acid thus contacts the substrates W and etches them.

[0104] The auxiliary transfer robot 12 includes a plurality of holders 23 that hold a plurality of substrates W in a vertical position, and an elevator 24 that vertically elevates the plurality of holders 23 between an upper position where the plurality of substrates W held in the holders 23 are upwardly removed from the fluoride-containing phosphoric acid in the inner tank 21, and a lower position (the position shown in FIG9 ) where the plurality of substrates W held in the holders 23 are immersed in the fluoride-containing phosphoric acid in the inner tank 21. The plurality of substrates W held in the holders 23 enter the inner tank 21 through an opening provided at the upper end of the inner tank 21 and exit the inner tank 21 through the opening.

[0105] Substrate processing apparatus 1 includes a circulation heating system that circulates and heats the fluoride-containing phosphoric acid within chemical solution treatment tank 6. The circulation heating system includes: a circulation pipe 25 that guides the fluoride-containing phosphoric acid within outer tank 22 to inner tank 21; a circulation pump 26 that transports the fluoride-containing phosphoric acid within circulation pipe 25 to inner tank 21; a heater 27 that heats the fluoride-containing phosphoric acid flowing within 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 within circulation pipe 25.

[0106] The circulation heating system further includes a chemical liquid nozzle 29. This chemical liquid nozzle 29 supplies fluoride-containing phosphoric acid supplied from the circulation piping 25 into the inner tank 21 by ejecting the fluoride-containing phosphoric acid from an ejection port 29p disposed within the inner tank 21, thereby creating an upward flow within the fluoride-containing phosphoric acid within the inner tank 21. Figure 9 shows an example in which two chemical liquid nozzles 29 are installed. In this example, the circulation piping 25 includes an upstream piping 25u extending downstream from the outer tank 22 and two downstream piping 25d branching from the upstream piping 25u. One chemical liquid nozzle 29 is attached to the downstream end of one downstream piping 25d, and the other chemical liquid nozzle 29 is attached to the downstream end of the other downstream piping 25d.

[0107] Inner tank 21, outer tank 22, circulation piping 25, and chemical nozzle 29 form a circulation path for circulating fluoride-containing phosphoric acid. The amount of fluoride-containing phosphoric acid in chemical treatment tank 6 exceeds the capacity of inner tank 21 (the maximum amount of fluoride-containing phosphoric acid that inner tank 21 can store). A circulation pump 26 continuously pumps fluoride-containing phosphoric acid from the upstream end of circulation piping 25 to the downstream end. Consequently, fluoride-containing phosphoric acid continuously overflows from inner tank 21 into outer tank 22 and circulates through the circulation path. While circulating through the circulation path, the fluoride-containing phosphoric acid is heated by heater 27, maintaining it at a constant temperature above 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, which discharges the fluoride-containing phosphoric acid from the circulation pipe 25 to the drain pipe 30, and a closed state, which does not discharge the fluoride-containing phosphoric acid 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] Substrate processing apparatus 1 includes a supply system for supplying fluoride-containing phosphoric acid to chemical processing tank 6. The supply system includes a pure water pipe 32 that conducts pure water from a pure water supply source to chemical processing tank 6; a phosphoric acid pipe 35 that conducts phosphoric acid from the phosphoric acid supply source to chemical processing tank 6; and a fluoride pipe 38 that conducts a fluoride-containing liquid from the fluoride supply source to chemical processing tank 6. The fluoride-containing liquid is a fluoride liquid or a solution obtained by dissolving fluoride. The fluoride concentration in the fluoride-containing liquid is higher than the fluoride concentration in the fluoride-containing phosphoric acid.

[0110] The supply system includes a pure water valve 34 installed in the pure water piping 32, a phosphoric acid valve 37 installed in the phosphoric acid piping 35, and a fluoride valve 40 installed in the fluoride piping 38. Phosphoric acid valve 37 switches between an open state, which allows the phosphoric acid solution in the phosphoric acid piping 35 to be supplied to the treatment tank 6, and a closed state, which prevents the phosphoric acid solution from being supplied to the treatment tank 6. The same applies to pure water valve 34 and fluoride valve 40.

[0111] Although not shown, the phosphoric acid valve 37 comprises a valve body with an internal flow path for liquid flow and an annular valve seat forming part of the internal flow path; a valve body movable relative to the valve seat; and an actuator that moves the valve body between a closed position, in which the valve body contacts the valve seat, and an open position, in which the valve body is separated from the valve seat. The same applies to other valves. The actuator can be a pneumatic actuator, an electric actuator, or other types of actuators. The control device 3 opens and closes the phosphoric acid valve 37 by controlling the actuator.

[0112] When the control device 3 opens phosphoric acid valve 37, that is, switches phosphoric acid valve 37 from a closed state to an open state, phosphoric acid in phosphoric acid piping 35 is supplied to the chemical liquid treatment tank 6. Similarly, when the control device 3 opens pure water valve 34, pure water in pure water piping 32 is supplied to the chemical liquid treatment tank 6. When the control device 3 opens fluoride valve 40, the fluoride-containing liquid in fluoride piping 38 is supplied to the chemical liquid treatment tank 6. 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. Figure 9 shows an example of supplying phosphoric acid and the like to the outer tank 22.

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

[0114] Similarly, if phosphoric acid or pure water is supplied to the chemical solution processing tank 6 from the phosphoric acid pipe 35 or the pure water pipe 32, the concentration of fluoride in the fluoride-containing phosphoric acid decreases according to the amount of phosphoric acid or pure water supplied. If a fluoride-containing liquid is supplied to the chemical solution processing tank 6 from the fluoride pipe 38, the concentration of fluoride in the fluoride-containing phosphoric acid increases according to the amount of 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 piping 32 to the chemical liquid 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 piping 35 to the chemical liquid treatment tank 6, and is also electrically connected to a fluoride flowmeter 39 that measures the flow rate of a fluoride-containing liquid supplied from the fluoride piping 38 to the chemical liquid treatment tank 6.

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

[0117] The control device 3 is electrically connected to a phosphoric acid concentration meter C1 for measuring the concentration of phosphoric acid in the fluoride-containing phosphoric acid, and a fluoride concentration meter C2 for measuring the concentration of fluoride in the fluoride-containing phosphoric acid. The control device 3 is further electrically connected to a thermometer T1 for detecting the temperature of the fluoride-containing phosphoric acid. Figure 9 shows an example in which the phosphoric acid concentration meter C1 and the fluoride concentration meter C2 measure the concentration of the fluoride-containing phosphoric acid in the inner tank 21, and the thermometer T1 measures the temperature of the fluoride-containing phosphoric acid in the inner tank 21. The phosphoric acid concentration meter C1 can measure the concentration of the fluoride-containing phosphoric acid in the outer tank 22, and can also measure the concentration of the fluoride-containing phosphoric acid in the circulation piping 25. The fluoride concentration meter C2 and the thermometer T1 are similar.

[0118] The control device 3 detects the concentration of phosphoric acid in the fluoride-containing phosphoric acid based on the value measured by the phosphoric acid concentration meter C1. If the detected phosphoric acid concentration differs 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 to bring the concentration of phosphoric acid in the fluoride-containing phosphoric acid closer to the set phosphoric acid concentration. This maintains 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 value measured by the fluoride concentration meter C2. If the detected fluoride concentration differs 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 bring the fluoride concentration in the fluoride-containing phosphoric acid closer to the set fluoride concentration. This maintains 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 value measured by 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. In this way, the temperature of the fluoride-containing phosphoric acid can be increased or decreased to maintain it at the etching temperature.

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

[0122] When the phosphoric acid set concentration, fluoride set concentration, and etching temperature are stored in the control device 3, the phosphoric acid set concentration, etc., can also be specified by a process recipe stored in the control device 3. A process recipe is information that specifies the processing content, processing conditions, and processing sequence of the substrate W. The control device 3 stores a plurality of process recipes. The plurality of process recipes differ from each other in at least one of the processing content, processing conditions, and processing sequence of the substrate W. The control device 3 controls the substrate processing apparatus 1 so that the substrate W is processed according to the process 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 rates of the silicon oxide film O1 and the silicon nitride film N1 are equal or substantially equal. In other words, the phosphoric acid set concentration, the fluoride set concentration, and the etching temperature are set so that the selectivity is 1 or substantially 1. Therefore, the silicon oxide film O1 and the silicon nitride film N1, which are in contact with the fluoride-containing phosphoric acid in the chemical solution treatment tank 6, are etched at equal or substantially equal etching rates.

[0124] The results shown in Figures 4 to 7 show that the selectivity decreases as the fluoride concentration in the fluoride-containing phosphoric acid increases, and increases or decreases as the temperature of the fluoride-containing phosphoric acid deviates from the isotropic temperature (the temperature at which the etching rates of the silicon oxide film and the silicon nitride film are equal). The phosphoric acid set concentration, fluoride set concentration, and etching temperature can also be set to intentionally achieve a selectivity different from 1.

[0125] FIG10 is a schematic diagram showing another example of the vertical cross section of the chemical solution treatment tank 6. As shown in FIG10 , FIG10 is a schematic diagram showing another example of the vertical cross section of the chemical solution treatment tank 6.

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

[0127] The supply system for supplying fluoride-containing phosphoric acid to the chemical liquid treatment tank 6 includes a mixing tank 41 that stores the fluoride-containing phosphoric acid to be supplied to the chemical liquid treatment tank 6; a supply pipe 42 that guides the fluoride-containing phosphoric acid from the mixing tank 41 to the chemical liquid treatment tank 6; and a supply pump 43 that delivers the fluoride-containing phosphoric acid from the mixing tank 41 to the chemical liquid treatment tank 6 via the supply pipe 42. The supply system further includes a recovery pipe 44 that guides the fluoride-containing phosphoric acid from the chemical liquid treatment tank 6 to the mixing tank 41; and a recovery valve 45 that switches between an open state, allowing the fluoride-containing phosphoric acid to flow from the recovery pipe 44 to the mixing tank 41, and a closed state, preventing the fluoride-containing phosphoric acid from flowing from the recovery pipe 44 to the mixing tank 41.

[0128] Supply piping 42 directs fluoride-containing phosphoric acid from mixing tank 41 to inner tank 21, while recovery piping 44 directs fluoride-containing phosphoric acid from outer tank 22 to mixing tank 41. Chemical nozzle 29 sprays the fluoride-containing phosphoric acid directed by supply piping 42 into inner tank 21. Chemical nozzle 29 can also spray fluoride-containing phosphoric acid into both inner tank 21 and outer tank 22. The mixing tank 41, supply piping 42, chemical nozzle 29, inner tank 21, outer tank 22, and recovery piping 44 form a circulation path for circulating the fluoride-containing phosphoric acid. A supply pump 43 continuously delivers the fluoride-containing phosphoric acid from the upstream end of supply piping 42 to the downstream end.

[0129] The upstream and downstream ends of the circulation pipe 25 are not connected to the inner tank 21 and the outer tank 22, but to the mixing tank 41. The mixing tank 41 and the circulation pipe 25 form a circulation path independent of the chemical treatment tank 6, that is, a circulation path that does not pass 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, pure water, and 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 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 and 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 also 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. Thus, the fluoride-containing phosphoric acid, whose concentrations of phosphoric acid, fluoride, and temperature are consistent or substantially consistent with the set phosphoric acid concentration, fluoride concentration, and etching temperature, can be supplied from the mixing tank 41 to the chemical solution processing tank 6, and the fluoride-containing phosphoric acid can be used to etch the plurality of substrates W in the inner tank 21.

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

[0132] Fig. 11A is a schematic top view showing the layout of a monolithic substrate processing apparatus 1 according to one embodiment of the present invention. Fig. 11B is a schematic side view showing the monolithic substrate processing apparatus 1.

[0133] As shown in Figure 11A, a substrate processing apparatus 1 is a single-wafer system that processes circular substrates W, such as semiconductor wafers, one by one. The apparatus 1 includes a load port LP that holds a carrier C containing the substrates W; a plurality of processing units 2 that process the substrates W transferred from the carrier C on the load port LP; a transfer system that transfers the substrates W between the carrier C on the load port LP and the plurality of processing units 2; and a control unit 3 that controls the apparatus 1.

[0134] The transport system includes an indexing robot IR, which loads and unloads substrates W from carriers C on the load port LP, and a central robot CR, which loads and unloads substrates W into and out of each processing unit 2. The indexing robot IR transports substrates W between the load port LP and the central robot CR, while the central robot CR transports substrates W between the indexing robot IR and the processing units 2. The central robot CR includes a hand H1 for supporting the substrates W, and the indexing robot IR includes a hand H2 for supporting the substrates W.

[0135] The processing units 2 form a plurality of towers TW arranged around the central robot CR in a plan view. Figure 11A shows an example of four towers TW. The central robot CR can move in and out of any of the towers TW. As shown in Figure 11B, each tower TW is composed of a plurality (e.g., three) of processing units 2 stacked one above the other.

[0136] FIG12 is a schematic diagram showing the interior of the horizontal observation processing unit 2. ...

[0137] The processing unit 2 includes: a box-shaped chamber 52 having an internal space; a rotating chuck 57 (substrate holder) which holds a substrate W horizontally in the chamber 52 while rotating around a vertical rotation axis A1 passing through the center of the substrate W; a plurality of nozzles which spray processing fluids such as processing liquid and processing gas equidirectionally toward the substrate W held on the rotating chuck 57; and a cylindrical processing cup 63 which receives the processing liquid scattered outward from the rotating chuck 57 and the substrate W.

[0138] The chamber 52 includes a box-shaped partition wall 53 with a loading / unloading port 53b for substrates W transported by the central robot CR (see Figure 11A ), and a shutter 54 that opens and closes loading / unloading port 53b. The FFU 51 (fan filter unit 51), which delivers clean air (filtered air) into the chamber 52, is located above an air supply port 53a formed on the top surface of the partition wall 53. The air supply port 53a is located at the upper end of the chamber 52, and an exhaust pipe 56, which exhausts the air within the chamber 52, is located at the lower end of the chamber 52.

[0139] The chamber 52 includes a rectifying plate 55 that divides the interior space of the chamber 52 into an upper space Su and a lower space SL. The upper space Su, between the top surface of the partition wall 53 and the upper surface of the rectifying plate 55, serves as a diffusion space for the clean air. The lower space SL, between the lower surface of the rectifying plate 55 and the floor of the partition wall 53, serves as a processing space for processing substrates W. A spin chuck 57 is positioned in the lower space SL. Substrates W are processed by creating a downflow of clean air 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 rotation base 59 that supports the plurality of chuck pins 58. The spin chuck 57 further includes a rotation shaft 60 extending downward from the center of the rotation base 59, an electric motor 61 that rotates the rotation shaft 60 to rotate the plurality of chuck pins 58 and the rotation base 59, and a chuck housing 62 that surrounds the electric motor 61. The spin chuck 57 may also be a vacuum chuck or other type of chuck.

[0141] The processing cup 63 includes a plurality of shields 64 that receive processing liquid scattered outward from the spin chuck 57 and substrate W, and a plurality of cups 65 that receive processing liquid directed downward by the shields 64. FIG12 shows an example in which two shields 64 and two cups 65 are provided, with the outermost cup 65 and the second outermost shield 64 being integrally formed.

[0142] The plurality of protective bodies 64 are connected to a protective body lifting unit 66 that lifts and lowers the plurality of protective bodies 64 individually in the vertical direction. The protective body lifting unit 66 positions the protective bodies 64 at any position within a range from an upper position to a lower position. FIG12 shows a state in which two protective bodies 64 are arranged in the lower position. The upper position is a position in which the upper end of the protective body 64 is arranged above the position where the substrate W is held by the rotary chuck 57. The lower position is a position in which the upper end of the protective body 64 is arranged below the position in which the substrate W is held by the rotary chuck 57. The position in which the substrate W is held by the rotary chuck 57 is a position in which the substrate W held by the rotary chuck 57 is arranged.

[0143] When supplying processing liquid to a rotating substrate W, the controller 3 controls the shield lifting unit 66 to position at least one shield 64 in the upper position. When processing liquid is supplied to the substrate W in this position, the processing liquid is flung outward from the substrate W. The flung processing liquid collides with the inner circumference of the shield 64, which is horizontally opposite the substrate W, and is directed into the cup 65 corresponding to the shield 64. Consequently, the processing liquid discharged from the substrate W is collected in the cup 65.

[0144] The multiple nozzles include: a heating fluid nozzle 67, which sprays heating liquid onto the upper surface of the substrate W held by the rotating chuck 57; a chemical liquid nozzle 71, which sprays fluoride-containing phosphoric acid onto the upper surface of the substrate W held by the rotating chuck 57; and a cleaning liquid nozzle 75, which sprays cleaning liquid onto the upper surface of the substrate W held by the rotating chuck 57.

[0145] The chemical liquid nozzle 71 can be a scanning nozzle that moves the chemical liquid relative to the impact position on the substrate W, or a fixed nozzle that cannot move the chemical liquid relative to the impact position on the substrate W. The same applies to the other nozzles. FIG12 shows an example in which the chemical liquid nozzle 71 and the heating fluid nozzle 67 are scanning nozzles, and the cleaning liquid nozzle 75 is a fixed nozzle.

[0146] In the example shown in FIG12 , the heating fluid nozzle 67 is connected to a nozzle moving unit 70, and the chemical liquid nozzle 71 is connected to a nozzle moving unit 74. The nozzle moving unit 74 horizontally moves the chemical liquid nozzle 71 between a processing position where the chemical liquid ejected from the chemical liquid nozzle 71 collides with the upper surface of the substrate W and a standby position where the chemical liquid nozzle 71 is positioned around the spin chuck 57 in a top view. The nozzle moving unit 70 is similarly configured.

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

[0148] Chemical nozzle 71 is connected to a chemical piping 72 that guides fluoride-containing phosphoric acid, an example of a chemical, from a chemical supply source to chemical nozzle 71. When control device 3 opens chemical valve 73 attached to chemical piping 72, chemical nozzle 71 sprays high-temperature (e.g., 100-150°C) fluoride-containing phosphoric acid. When control device 3 closes chemical valve 73, chemical nozzle 71 stops spraying fluoride-containing phosphoric acid.

[0149] The fluoride-containing phosphoric acid supplied to the chemical nozzle 71 is, for example, the fluoride-containing phosphoric acid in the mixing tank 41 shown in FIG10 . Thus, the fluoride-containing phosphoric acid having a phosphoric acid concentration, a fluoride concentration, and a temperature that are consistent or substantially consistent with the set phosphoric acid concentration, the set fluoride concentration, and the etching temperature can be ejected into the chemical nozzle 71 and supplied to the substrate W held on the spin chuck 57 .

[0150] When supplying the fluoride-containing phosphoric acid in the mixing tank 41 shown in FIG10 to the chemical nozzle 71, the chemical pipe 72 can be connected directly to the mixing tank 41 or connected to the mixing tank 41 via the circulation pipe 25. In the former case, the supply pipe 42 shown in FIG10 can also be used as the chemical pipe 72. More specifically, the chemical nozzle 71 and the chemical valve 73 can be installed on the supply pipe 42 serving as the chemical pipe 72. The fluoride-containing phosphoric acid collected in the cup 65 can also be recovered in the mixing tank 41 via the recovery pipe 44.

[0151] Cleaning liquid nozzle 75 is connected to a cleaning liquid pipe 76 that guides pure water, an example of a cleaning liquid, from a cleaning liquid supply source to cleaning liquid nozzle 75. When control device 3 opens cleaning liquid valve 77 attached to cleaning liquid pipe 76, cleaning liquid nozzle 75 sprays cleaning liquid. When control device 3 closes cleaning liquid valve 77, cleaning liquid nozzle 75 stops spraying cleaning liquid. The cleaning liquid sprayed from cleaning liquid nozzle 75 can be at room temperature, above room temperature, or below room temperature.

[0152] A substrate W with exposed silicon oxide film O1 and silicon nitride film N1, as shown in FIG1F , is transported to substrate processing apparatus 1. A transport system loads a substrate W from carrier C on load port LP into processing unit 2. After the loaded substrate W is processed in processing unit 2, the transport system transfers the processed substrate W from processing unit 2 to carrier C on load port LP. Thus, substrates W loaded into substrate processing apparatus 1 via load port LP are processed in processing unit 2 and then unloaded from substrate processing apparatus 1 via load port LP.

[0153] After the central robot CR transfers a substrate W to the spin chuck 57, the control device 3 causes the spin chuck 57 to hold and rotate the substrate W. In this state, the control device 3 controls the heating fluid nozzle 67, the chemical nozzle 71, and the cleaning fluid nozzle 75 to sequentially discharge phosphoric acid, fluoride-containing phosphoric acid, and pure water. This sequentially supplies phosphoric acid, fluoride-containing phosphoric acid, and pure water to the entire upper surface of the substrate W. The control device 3 then dries the substrate W by rotating the spin chuck 57 at high speed. After the substrate W is dried, the control device 3 stops the spin chuck 57 and releases its grip on the substrate W. The control device 3 then controls the central robot CR to transfer the processed substrate W from the spin chuck 57.

[0154] As described above, in this embodiment, phosphoric acid containing fluoride, i.e., fluoride-containing phosphoric acid, is brought into contact with the silicon oxide film O1 and the silicon nitride film N1 formed on the substrate W, thereby etching the silicon oxide film O1 and the silicon nitride film N1 using the fluoride-containing phosphoric acid. The fluoride-containing phosphoric acid is maintained at an etching temperature that is consistent with or close to the iso-rate temperature at which the etching rates of the silicon oxide film O1 and the silicon nitride film N1 are equal, depending on 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 substantially equal etching rates.

[0155] In this embodiment, phosphoric acid containing fluoride, which has an etching temperature of fluoride, is brought into contact with the silicon oxide film O1 and the silicon nitride film N1 formed on the substrate W. The fluoride increases the etching rate of the silicon oxide film O1 and the etching rate of the silicon nitride film N1. As a result, the silicon oxide film O1 can be etched at a higher etching rate than when the silicon oxide film O1 is etched using phosphoric acid without fluoride, and the silicon nitride film N1 can be etched at a higher etching rate than when the silicon nitride film N1 is etched using phosphoric acid without fluoride. As a result, the processing time of the substrate W can be shortened, thereby reducing energy consumption such as electricity.

[0156] In this embodiment, a fluoride-containing phosphoric acid whose selectivity varies with temperature is maintained at or near the constant-rate 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 fluoride concentration in the fluoride-containing phosphoric acid is constant, the selectivity is not constant regardless of the temperature of the fluoride-containing phosphoric acid, but rather 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 with a selectivity of 1 or near 1, or with a selectivity exceeding or falling below 1.

[0157] In this embodiment, phosphoric acid containing a fluoride at an etching temperature suitable for ammonium fluoride or ammonium bifluoride 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 and the silicon nitride film N1 to be etched at equal or substantially equal etching rates. When the fluoride is an alkali metal fluoride such as sodium fluoride (NaF) or potassium fluoride (KF), there is a concern that the substrate W may be contaminated by the metal. However, when the fluoride is ammonium fluoride or ammonium bifluoride, this concern is eliminated. Therefore, the cleanliness of the substrate W can be prevented from being degraded, and the silicon oxide film O1 and the silicon nitride film N1 can be etched as described above.

[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. The fluoride-containing phosphoric acid at this temperature is then 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 with a selectivity within a range of 0.9 to 1.1. This prevents the silicon oxide film O1 from being substantially etched, as occurs when etching the silicon oxide film O1 and the silicon nitride film N1 using fluoride-free phosphoric acid. On the other hand, the silicon nitride film N1 is etched at a higher rate than the silicon oxide film O1.

[0159] In this embodiment, fluoride-containing phosphoric acid at an etching temperature is supplied to the memory hole 104, which 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 fluoride-containing phosphoric acid contacts the plurality of silicon oxide films O1 and the plurality of silicon nitride films N1 that constitute the inner circumference 105 of the memory hole 104, thereby etching them. If the longitudinal cross-section of the inner circumference 105 of the memory hole 104 before etching (a cross-section taken along a plane parallel to the thickness direction Dt of the substrate W and including the centerline of the memory hole 104) is linear, etching the inner circumference 105 of the memory hole 104 with phosphoric acid that does not contain fluoride may cause the longitudinal cross-section of the inner circumference 105 of the memory hole 104 to change to a wavy line. Supplying fluoride-containing phosphoric acid at an etching temperature into the memory hole 104 can prevent or mitigate this change.

[0160] In this embodiment, before supplying fluoride-containing phosphoric acid at an etching temperature to the memory hole 104, whose diameter varies depending on the position in the thickness direction Dt of the substrate W, a portion of the inner circumference 105 of the memory hole 104 in the thickness direction Dt of the substrate W is covered entirely with a protective material such as a protective film 115. Subsequently, the fluoride-containing phosphoric acid at an etching temperature is brought into contact with the remaining portion of the inner circumference 105 of the memory hole 104 not covered by the protective material. This selectively etches the remaining portion of the inner circumference 105 of the memory hole 104, allowing the shape of the memory hole 104 to be intentionally changed.

[0161] In this embodiment, the substrate W is heated and maintained at a constant temperature before the heated fluoride-containing phosphoric acid maintained at an etching temperature is brought into contact with the substrate W. This allows the silicon oxide film O1 and the silicon nitride film N1 to be etched in a shorter time than when the fluoride-containing phosphoric acid at an etching temperature is supplied to the substrate W at room temperature. Furthermore, the temperature of the substrate W is stabilized before contact with the fluoride-containing phosphoric acid. Therefore, when multiple substrates W are sequentially brought into contact with the fluoride-containing phosphoric acid at an etching temperature, the etching amount can be stabilized across the multiple substrates W. Another embodiment

[0162] 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 an ellipse, a polygon, or other shapes other than a circle.

[0163] The diameter of the memory hole 104 may decrease in stages rather than continuously as it approaches the bottom of the memory hole 104. The inner circumference 105 of the memory hole 104 may also include a portion where the diameter of the memory hole 104 decreases continuously as it approaches the bottom of the memory hole 104, and a portion where the diameter of the memory hole 104 decreases in stages as it approaches the bottom of the memory hole 104.

[0164] The diameter of the memory hole 104 may increase continuously or in stages as it approaches the bottom of the memory hole 104 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 also 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 in stages as it approaches the bottom of the memory hole 104.

[0165] The inner circumference 105 of the memory hole 104 may also include a portion where the diameter of the memory hole 104 decreases continuously or in stages 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 stages as it approaches the bottom of the memory hole 104 .

[0166] When etching the inner circumference of a hole such as memory hole 104 using an etching solution, the etching solution becomes more difficult to replace as the bottom of memory hole 104 is approached, resulting in a tendency for the etching rate to decrease as the bottom of memory hole 104 is approached. If the diameter of memory hole 104 increases as the bottom of memory hole 104 is approached, etching the inner circumference 105 of memory hole 104 using fluoride-containing phosphoric acid can reduce the unevenness in the diameter of memory hole 104. In this case, there is no need to use protective film 115 to protect the inlet-side portion 105e of the inner circumference 105 of memory hole 104 from damage by the fluoride-containing phosphoric acid, and therefore, the supply of the aforementioned filling solution 111 and protective solution 114 to substrate W is not necessary.

[0167] The structure of the substrate W to which the fluoride-containing phosphoric acid is applied at an etching temperature is not limited to that shown in FIG. 1A and other figures. The surface etched by the fluoride-containing phosphoric acid may be the inner circumference of a hole other than the memory hole 104, or the side surface of a trench extending through the thickness direction Dt of the substrate W by alternating layers of silicon oxide films O1 and silicon nitride films N1. The surface etched by the fluoride-containing phosphoric acid may also be a plane perpendicular to the thickness direction Dt of the substrate W.

[0168] Alternatively, the substrate W may be heated before etching using fluoride-containing phosphoric acid, instead of or in addition to heating the substrate W by contacting the heating liquid with the substrate W. A heating gas at a higher temperature than room temperature (e.g., a temperature in the range of 100-150°C) may be brought into contact with the substrate W. The heating gas may be an inert gas such as nitrogen, clean air (filtered air), or any other gas.

[0169] Alternatively, a heating fluid having a temperature higher than room temperature, such as a heating liquid or heating gas, may be brought into contact with the substrate W, or alternatively, a heater that generates heat through the supply of electrical power may be used to heat the substrate W prior to etching with fluoride-containing phosphoric acid. For example, the heater may be positioned above or below the substrate W as shown in FIG12 .

[0170] It is also possible to omit the heating of the substrate W before etching. That is, phosphoric acid containing fluoride at an 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 disc-shaped substrate W, but may also be an apparatus for processing a polygonal substrate W.

[0172] Two or more of the above-mentioned structures may be combined. Two or more of the above-mentioned steps may be combined.

[0173] The embodiments of the present invention have been described in detail, but these are merely specific examples used to clarify the technical content of the present invention. The present invention should not be limited to these specific examples. The scope of the present invention is limited only by the scope of the attached patent claims. [Related Applications]

[0174] This application claims priority based on Japanese Patent Application No. 2022-080692 filed on May 17, 2022, the entire contents of which are incorporated herein by reference.

[0175] 1: Substrate processing equipment 2: Processing unit 3: Control device 4: Liquid treatment tank 5:Heat treatment tank 6: Liquid treatment tank 7: Cleaning tank 8: Drying tank 9: Carrier transport device 10: Posture-changing robot 11: Main transport robot 12: Auxiliary transport robot 21: Inner groove 22: Outer groove 23: Holder 24: Lifter 25: Circulation piping 25d: Downstream piping 25u: Upstream piping 26: Circulation pump 27: Heater 28:Filter 29: Liquid nozzle 29p: Spout 30: Drainage piping 31: Drain valve 32: Pure water piping 33:Pure water flow meter 34:Pure water valve 35: Phosphoric acid piping 36: Phosphoric acid flow meter 37: Phosphoric acid valve 38: Fluoride piping 39: Fluoride flow meter 40: Fluoride valve 41:Mixing tank 42: Supply piping 43: Supply pump 44: Recovery piping 45: Recovery valve 51:FFU 52: Chamber 53: Next door 53a: Air outlet 53b: Moving in and out 54: Baffle 55:Rectifier 56: Exhaust pipe 57: Rotating chuck 58: Chuck pin 59: Rotating base 60: Rotation axis 61: Electric Motor 62: chuck housing 63: Processing cup body 64: Protective Body 65: cup body 66: Protective body lifting unit 67: Heating fluid nozzle 68: Heating liquid piping 69: Heating liquid valve 70: Nozzle moving unit 71: Liquid nozzle 72: Liquid piping 73: Liquid valve 74: Nozzle moving unit 75: Cleaning fluid nozzle 76: Cleaning fluid piping 77: Cleaning fluid valve 101: Base material 102: Laminated film 103: The most superficial 104:Memory hole 105: Inner Surface 105b: bottom part 105e: Entrance side 111:Filling fluid 112: Filling material 112r: Residual filling material 113: Removal liquid 114: Protective fluid 115: Protective film 116:Thin film A1: Rotation axis C:Carrier C1: Phosphoric acid concentration meter C2: Fluoride concentration meter CR: Center Robot Dp: surface direction Dt: thickness direction H1: Hand H2: Hands IR: Indexing Robot LP: Loading Port O1: Silicon oxide film N1: Silicon nitride film SL: Lower Space Su: Upper Space T1: Thermometer TW:Tower W: substrate

Claims

1. A substrate processing method comprising: a phosphoric acid heating step, wherein the phosphoric acid containing fluoride, i.e., fluoride-containing phosphoric acid, is heated to such that the ratio of the etching rate of the silicon nitride film to the etching rate of the silicon oxide film is in the range of 0.9 to 1.1, and the fluoride-containing phosphoric acid is maintained at an etching temperature that is consistent with or close to an isochronous temperature at which the etching rates of the silicon oxide film and the silicon nitride film are equal at the concentration of the fluoride in the fluoride-containing phosphoric acid. The phosphoric acid supply process involves contacting the fluorinated phosphoric acid at the aforementioned etching temperature with the silicon oxide film and silicon nitride film formed on the substrate, thereby etching the silicon oxide film and silicon nitride film using the fluorinated phosphoric acid; and the cleaning solution supply process involves rinsing away the fluorinated phosphoric acid by supplying a cleaning solution to the substrate while the silicon oxide film and silicon nitride film remain on the substrate.

2. A substrate processing method, comprising processing a substrate, wherein the substrate comprises: a plurality of silicon oxide films and a plurality of silicon nitride films, which are deposited in the thickness direction of the substrate in an alternating manner between the silicon oxide films and the silicon nitride films; and a hole recessed from the outermost surface of the substrate in the thickness direction, penetrating the plurality of silicon oxide films and the plurality of silicon nitride films in the thickness direction; the diameter of the hole varies according to its position in the thickness direction of the substrate; the substrate processing method comprises: The phosphoric acid heating process involves heating phosphoric acid containing fluoride, i.e., phosphoric acid containing fluoride, to make the ratio of the etching rate of the silicon nitride film to the etching rate of the silicon oxide film within the range of 0.9 to 1.1, and maintaining the phosphoric acid containing fluoride at an etching temperature that is consistent with or close to the isochronous temperature at which the etching rates of the silicon oxide film and the silicon nitride film are equal at the concentration of fluoride in the phosphoric acid containing fluoride. The phosphoric acid supply process involves etching the silicon oxide and silicon nitride films by contacting the phosphoric acid containing fluoride at the aforementioned etching temperature with the plurality of silicon oxide films and the plurality of silicon nitride films exposed in the aforementioned holes using the phosphoric acid containing fluoride; and the inner peripheral surface protection process involves covering a portion of the inner peripheral surface of the aforementioned holes in the thickness direction of the substrate with a solid, liquid, or semi-solid protective material that protects the silicon oxide and silicon nitride films from damage by the phosphoric acid containing fluoride; and the phosphoric acid supply process includes the step of protecting the aforementioned portion of the holes from damage by the phosphoric acid containing fluoride at the aforementioned etching temperature using the protective material, while contacting the remaining portion of the inner peripheral surface of the holes not covered by the protective material with the phosphoric acid containing fluoride at the aforementioned etching temperature.

3. The substrate processing method of claim 1 or 2, wherein the fluoride is a compound that increases the etching rate of the silicon oxide film and the etching rate of the silicon nitride film.

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

5. The substrate processing method of claim 1 or 2, wherein the fluoride is ammonium fluoride or ammonium difluoride.

6. The substrate processing method of claim 1 or 2, wherein the ratio of the etching rate of the silicon nitride film etched in the phosphoric acid supply process to the etching rate of the silicon oxide film etched in the phosphoric acid supply process is selected to be in the range of 0.9 to 1.

1.

7. The substrate processing method of claim 1 or 2 further includes a substrate heating step, wherein the substrate is maintained at a fixed temperature by heating the substrate before the phosphoric acid containing fluoride at the etching temperature is brought into contact with the silicon oxide film and silicon nitride film formed on the substrate.

8. A substrate processing apparatus comprising: a heater that maintains the phosphoric acid containing fluoride at an etching temperature such that the etching rate of a silicon nitride film is in the range of 0.9 to 1.1 by heating phosphoric acid containing fluoride, i.e., phosphoric acid containing fluoride, so that the etching rate of a silicon nitride film is in the range of 0.9 to 1.

1. The etching temperature is consistent with or close to an isochronous temperature at which the etching rate of the silicon oxide film and the etching rate of the silicon nitride film are equal at the concentration of fluoride in the phosphoric acid containing fluoride. The device includes a chemical nozzle that sprays phosphoric acid containing fluoride at the aforementioned etching temperature, and etches the silicon oxide film and silicon nitride film formed on the substrate by contacting the sprayed phosphoric acid containing fluoride at the aforementioned etching temperature with the silicon oxide film and silicon nitride film formed on the substrate; and a cleaning fluid nozzle that washes away the phosphoric acid containing fluoride by supplying cleaning fluid to the substrate while the silicon oxide film and silicon nitride film remain on the substrate.

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