Etching method

Abstract

One aspect of the present invention provides an etching method capable of suppressing variations in etching speed between the etching speed when an etching liquid is initially used and the etching speed when the etching liquid is reused.　The present disclosure relates to an etching method including a step for etching, with an etching liquid, a layer to be etched that includes a Group 6 element metal. The etching liquid contains component A, component B, component C, component D, component E, and a Group 6 element metal ion, the content of the Group 6 element metal ion being 0.005 mass% or more, the mass ratio of component E to the Group 6 element metal ion (component E / the Group 6 element metal ion) being 1 or more. Component A: phosphoric acid, component B: nitric acid, component C: water, component D: a polyvalent amine having an average molecular weight of 300 or more, component E: a nitrogen-containing basic compound (excluding component D)

Description

Etching Method

[0001] The present disclosure relates to an etching method.

[0002] In the manufacturing process of semiconductor devices, a step is carried out in which a layer to be etched containing at least one metal, such as tungsten, tantalum, zirconium, hafnium, molybdenum, niobium, ruthenium, osmium, rhenium, rhodium, copper, nickel, cobalt, titanium, titanium nitride, alumina, aluminum, and iridium, is etched into a predetermined pattern shape. In the field of semiconductors in recent years, high integration has progressed, and more complex and finer wiring is required. This has led to increasing demands for pattern processing techniques and etching solutions, and various etching solutions have been proposed.

[0003] For example, Japanese Patent Laid-Open Publication No. 2024-37160 (Patent Document 1) proposes an etching solution composition for etching a layer to be etched containing at least one metal, the etching solution composition comprising nitric acid, a polyamine having a number average molecular weight of 300 or more, a nitrogen-containing basic compound having a molecular weight of less than 300, and water. Japanese Patent Laid-Open Publication No. 2024-37705 (Patent Document 2) proposes a method for producing an etching solution composition for etching a metal film (film to be etched) formed on a substrate, the method comprising filling the etching solution composition into a container using a filling nozzle having a filling port for discharging the etching solution composition, wherein the receding contact angle of the etching solution with respect to the material of the filling port of the filling nozzle is 60° or more and the ratio of the advancing contact angle to the receding contact angle (advancing contact angle / receding contact angle) is 1.4 or less. Claim 3 and other sections of this document state that the etching solution composition contains phosphoric acid, nitric acid, an organic acid, an etching inhibitor, and water.

[0004] In one aspect, the present disclosure relates to an etching method including a step of etching a layer to be etched that contains a Group 6 element metal with an etching solution, wherein the etching solution contains the following components A, B, C, D, and E, and Group 6 element metal ions, wherein the content of the Group 6 element metal ions in the etching solution is 0.005 mass% or more, and the mass ratio of component E to the Group 6 element metal ions (component E / Group 6 element metal ions) is 1 or more: component A: phosphoric acid; component B: nitric acid; component C: water; component D: a polyvalent amine having an average molecular weight of 300 or more; component E: a nitrogen-containing basic compound (excluding component D);

[0005] In one aspect, the present disclosure relates to an etching method including a step of etching a layer to be etched that contains a Group 6 element metal with an etching solution, wherein the etching solution is a blend of the following components A, B, C, D, and E, and contains a Group 6 element metal ion, wherein the content of the Group 6 element metal ion in the etching solution is 0.005 mass% or more, and the mass ratio of component E to the Group 6 element metal ion (component E / Group 6 element metal ion) is 1 or more: component A: phosphoric acid; component B: nitric acid; component C: water; component D: a polyvalent amine having an average molecular weight of 300 or more; component E: a nitrogen-containing basic compound (excluding component D);

[0006] As an etching solution, a mixed acid aqueous solution (strong acid aqueous solution) containing nitric acid is commonly used. Patent Documents 1 and 2 propose adding an etching inhibitor such as polyethyleneimine as an agent for suppressing etching and improving etching selectivity. In an etching solution containing an added etching inhibitor, the etching inhibitor interacts with metals (e.g., Group 6 element metals) dissolved from the layer to be etched as etching progresses, so the etching rate increases over time as the etching solution is reused more frequently. On the other hand, if an excessive amount of etching inhibitor is present in the etching solution from the beginning (first etching), etching is excessively suppressed, resulting in a decrease in productivity.

[0007] Therefore, in one aspect, the present disclosure provides an etching method that can suppress the variation in etching rate between the etching rate when the etching liquid is used for the first time and the etching rate when the etching liquid is reused, even when the etching liquid is reused.

[0008] According to one aspect of the present disclosure, an etching method can be provided that can suppress the variation in etching rate between the etching rate when the etching liquid is used for the first time and the etching rate when the etching liquid is reused, even when the etching liquid is reused.

[0009] As a result of intensive research, the present inventors have found that by using an etching solution having a content of Group 6 element metal ions of 0.005 mass % or more and a mass ratio of the nitrogen-containing basic compound (excluding polyvalent amines having an average molecular weight of 300 or more) to the Group 6 element metal ions of a predetermined value or more, the etching rate when reused can be maintained within an appropriate range, and the variation in etching rate between the etching rate when used for the first time and the etching rate when reused can be suppressed.

[0010] In one aspect, the present disclosure relates to an etching method (hereinafter also referred to as the "etching method of the present disclosure") that includes a step of etching a layer to be etched that contains a Group 6 element metal with an etching solution (hereinafter also referred to as the "etching step"), in which the etching solution contains the following components A, B, C, D, and E, and Group 6 element metal ions, the content of the Group 6 element metal ions being 0.005 mass% or more, and the mass ratio of component E to the Group 6 element metal ions (component E / Group 6 element metal ions) being 1 or more: component A: phosphoric acid; component B: nitric acid; component C: water; component D: a polyvalent amine having an average molecular weight of 300 or more; component E: a nitrogen-containing basic compound (excluding component D).

[0011] Although the details of the mechanism by which the effects of the present disclosure are realized are not clear, it is speculated as follows. When an etching solution containing an etching inhibitor such as polyethyleneimine is used, it is believed that the etching rate can be suppressed by the etching inhibitor being adsorbed to a certain amount on the layer to be etched. However, if the reused etching solution contains a Group 6 element metal dissolved from the layer to be etched, the etching inhibitor interacts with the Group 6 element metal dissolved in the etching solution, making it impossible to maintain the etching rate within an appropriate range when the etching solution is reused. As the number of times the etching solution is reused increases, the etching rate tends to increase over time. In the present disclosure, by using an etching solution containing 0.005 mass% or more of a Group 6 element metal ion and in which the mass ratio of a nitrogen-containing basic compound (component E) to the Group 6 element metal ion is equal to or greater than a predetermined value, even if the etching solution contains 0.005 mass% or more of a Group 6 element metal ion, a specific etching inhibitor (a polyvalent amine having an average molecular weight of 300 or more: component D) is adsorbed to the layer to be etched in a certain amount, thereby maintaining the etching rate within an appropriate range and suppressing the variation in etching rate between the etching rate when the etching solution is used for the first time and the etching rate when the etching solution is reused. However, the present disclosure need not be interpreted as being limited to these mechanisms.

[0012] [Layer to be etched] In the present disclosure, the layer to be etched is a layer to be etched containing a Group 6 element metal. Examples of the Group 6 element metal include at least one metal selected from tungsten and molybdenum. In one or more embodiments, the layer to be etched may be a tungsten film (layer) or a molybdenum film (layer).

[0013] [Etching Step] In one or more embodiments, the etching step in the etching method of the present disclosure includes etching a layer to be etched that contains a Group 6 element metal, using an etching solution that contains Component A, Component B, Component C, Component D, Component E, and Group 6 element metal ions. In one or more embodiments, the etching solution that contains Group 6 element metal ions in the present disclosure is an etching solution that has been used one or more times in the etching step (hereinafter also referred to as a "reused etching solution").

[0014] In the etching step, examples of the etching method include immersion etching and single wafer etching.

[0015] In one or more embodiments, when the layer to be etched is a tungsten film, the temperature of the etching solution (etching temperature) in the etching step of the present disclosure is, from the viewpoint of uniform etching of the layer to be etched, preferably 0° C. or higher, more preferably 50° C. or higher, even more preferably 70° C. or higher, and preferably 150° C. or lower, more preferably 130° C. or lower, and even more preferably 110° C. or lower. More specifically, in one or more embodiments, when the layer to be etched is a tungsten film, the etching temperature is preferably 0° C. or higher and 150° C. or lower, more preferably 50° C. or higher and 130° C. or lower, and even more preferably 70° C. or higher and 110° C. or lower. In one or more embodiments, when the layer to be etched is a molybdenum film, the temperature of the etching solution (etching temperature) in the etching step of the present disclosure is, from the viewpoint of uniform etching of the layer to be etched, preferably 0° C. or higher, more preferably 15° C. or higher, even more preferably 20° C. or higher, and preferably 80° C. or lower, more preferably 65° C. or lower, and even more preferably 50° C. or lower. More specifically, in one or more embodiments, when the layer to be etched is a molybdenum film, the etching temperature is preferably 0° C. or higher and 80° C. or lower, more preferably 15° C. or higher and 65° C. or lower, and even more preferably 20° C. or higher and 50° C. or lower.

[0016] In the etching step, the etching time can be set to, for example, 1 minute or more and 180 minutes or less.

[0017] [Etching Solution] In one or more embodiments, the etching solution used in the etching step is a reused etching solution, and contains component A, component B, component C, component D, component E, and a Group 6 element metal ion. Each component contained in the etching solution will be described below.

[0018] (Group 6 element metal ions) In one or more embodiments, the Group 6 element metal ions contained in the etching solution (etching solution when reused) used in the etching step are derived from the Group 6 element metal contained in the layer to be etched, and in one or more embodiments, are Group 6 element metal dissolved from the layer to be etched. In one or more embodiments, the Group 6 element metal is at least one selected from tungsten and molybdenum. The Group 6 element metal (ions) in the etching solution may be one type or a combination of two or more types.

[0019] The concentration (content, solubility) of the Group 6 element metal in the etching solution used in the etching step (the etching solution when reused) can be measured using ICP or the like. For example, the content of Group 6 element metal ions in the etching solution is 0.005% by mass or more, and in one or more embodiments, 0.01% by mass or more or 0.1% by mass or more. In one or more embodiments, the content of Group 6 element metal ions in the etching solution is preferably 1% by mass or less, more preferably 0.8% by mass or less, and even more preferably 0.6% by mass or less, from the viewpoint of keeping the etching rate at a certain level or less. When two or more types of Group 6 element metal ions are used in combination, the content of the Group 6 element metal ions is the total content thereof.

[0020] (Component A: Phosphoric Acid) The amount of phosphoric acid (hereinafter also referred to as "Component A") in the etching solution used in the etching step (the etching solution when reused) is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more, from the viewpoint of uniform etching of the layer to be etched, and from the same viewpoint, is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less. More specifically, the amount of phosphoric acid in the etching solution used in the etching step is preferably 40% by mass or more and 90% by mass or less, more preferably 50% by mass or more and 85% by mass or less, and even more preferably 60% by mass or more and 80% by mass or less.

[0021] The mass ratio of component A to Group 6 element metal ions (component A / Group 6 element metal ions) in the etching solution used in the etching step (the etching solution when reused) is preferably 10 or more, more preferably 50 or more, and more preferably 100 or more, from the viewpoint of optimizing the etching rate, and from the same viewpoint, is preferably 10,000 or less, more preferably 5,000 or less, and even more preferably 1,000 or less.

[0022] (Component B: Nitric Acid) The amount of nitric acid (hereinafter also referred to as "Component B") in the etching solution used in the etching step (etching solution when reused) is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 1.5% by mass or more from the viewpoint of improving the etching rate, and is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 8% by mass or less from the viewpoint of uniform etching of the layer to be etched. More specifically, the amount of nitric acid in the etching solution used in the etching step is preferably 0.5% by mass or more and 20% by mass or less, more preferably 1% by mass or more and 10% by mass or less, and even more preferably 1.5% by mass or more and 8% by mass or less.

[0023] The mass ratio of component B to Group 6 element metal ions (component B / Group 6 element metal ions) in the etching solution used in the etching step (the etching solution when reused) is preferably 1 or more, more preferably 5 or more, and more preferably 10 or more, from the viewpoint of optimizing the etching rate, and from the same viewpoint, is preferably 1,000 or less, more preferably 500 or less or 300 or less, and even more preferably 100 or less.

[0024] (Component C: Water) Examples of water (hereinafter also referred to as "component C") contained in the etching solution (etching solution when reused) used in the etching step include distilled water, ion-exchanged water, pure water, and ultrapure water. From the viewpoint of uniform etching of the layer to be etched, the amount of water in the etching solution (etching solution when reused) used in the etching step is preferably 2% by mass or more, more preferably 5% by mass or more, and even more preferably 7% by mass or more, and from the same viewpoint, preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less. More specifically, the amount of water in the etching solution used in the etching step is preferably 2% by mass or more and 30% by mass or less, more preferably 5% by mass or more and 25% by mass or less, and even more preferably 7% by mass or more and 20% by mass or less.

[0025] (Component D: Polyvalent Amine with Average Molecular Weight of 300 or More) In one or more embodiments, the polyvalent amine with an average molecular weight of 300 or more (hereinafter also referred to as "Component D") contained in the etching solution used in the etching step (etching solution when reused) can be at least one compound selected from a compound having a repeating unit derived from ethyleneimine, a compound having a repeating unit derived from allylamine, and a compound having a repeating unit derived from diallylamine. Among these, from the viewpoint of etching suppression, it is preferable to contain a compound having a repeating unit derived from ethyleneimine. The content of the compound having a repeating unit derived from ethyleneimine in Component D is preferably 10% by mass or more, more preferably 50% by mass or more, and preferably 100% by mass. Component D may be used alone or in combination of two or more types. Examples of the compound having a repeating unit derived from ethyleneimine include polyethyleneimine (PEI). Examples of the compound having a repeating unit derived from allylamine include allylamine hydrochloride polymer, allylamine polymer, etc. Examples of the compound having a repeating unit derived from diallylamine include diallylamine polymer, diallylamine / sulfur dioxide copolymer, etc.

[0026] From the viewpoint of etching inhibition, the average molecular weight of component D is 300 or more, preferably 600 or more, more preferably 1,000 or more, and preferably 100,000 or less, more preferably 50,000 or less, and even more preferably 10,000 or less. In one or more embodiments of the present disclosure, the average molecular weight of component D is a number average molecular weight, and in one or more embodiments, it is a weight average molecular weight. In one or more embodiments, from the viewpoint of etching inhibition, the number average molecular weight of the compound having an ethyleneimine-derived repeating unit is preferably 300 or more, more preferably 600 or more, and even more preferably 1,200 or more, and from the viewpoint of viscosity, it is preferably 100,000 or less, more preferably 10,000 or less, and even more preferably 5,000 or less. More specifically, the number average molecular weight of the compound having an ethyleneimine-derived repeating unit is preferably 300 or more and 100,000 or less, more preferably 600 or more and 10,000 or less, and even more preferably 1,200 or more and 5,000 or less. In one or more embodiments, the weight-average molecular weight of the compound having a repeating unit derived from allylamine is preferably 1,000 or more, more preferably 2,000 or more, and even more preferably 3,000 or more, from the viewpoint of etching inhibition; and is preferably 50,000 or less, more preferably 10,000 or less, and even more preferably 7,000 or less, from the viewpoint of viscosity. More specifically, the weight-average molecular weight of the compound having a repeating unit derived from allylamine is preferably 1,000 or more and 50,000 or less, more preferably 2,000 or more and 10,000 or less, and even more preferably 3,000 or more, from the viewpoint of etching inhibition. and is preferably 50,000 or less, more preferably 10,000 or less, and even more preferably 7,000 or less, from the viewpoint of viscosity. More specifically, the weight average molecular weight of the compound having a repeating unit derived from diallylamine is preferably 1,000 or more and 50,000 or less, more preferably 2,000 or more and 10,000 or less, and even more preferably 3,000 or more and 7,000 or less.

[0027] An example of a method for measuring the average molecular weight (number average molecular weight and weight average molecular weight) of component D of the present disclosure is shown below. <GPC conditions (compounds having repeating units derived from ethyleneimine, compounds having repeating units derived from allylamine, and compounds having repeating units derived from diallylamine)> Sample solution: adjusted to a concentration of 0.1 wt% Apparatus / detector: HLC-8320GPC (integrated GPC) manufactured by Tosoh Corporation Column: α-M + α-M (manufactured by Tosoh Corporation) Eluent: 0.15 mol / L NaSO, 1% CHCOOH / water Column temperature: 40°C Flow rate: 1.0 mL / min Sample solution injection amount: 100 μL Standard polymer: pullulan with known molecular weight (Shodex P-5, P-50, P-200, P-800)

[0028] The amount of component D in the etching solution used in the etching step (etching solution when reused) is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, from the viewpoint of maintaining an etching rate at or below a certain level. Also, from the viewpoint of maintaining an etching rate at or above a certain level, the amount is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less. More specifically, the amount of component D in the etching solution used in the etching step (etching solution when reused) is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.05% by mass or more and 5% by mass or less, and even more preferably 0.1% by mass or more and 3% by mass or less. When component D is a combination of two or more types, the amount of component D is the total amount thereof. When component D contains a compound having a repeating unit derived from ethyleneimine, the amount of the compound having an ethyleneimine repeating unit in the etching solution used in the etching step (etching solution when reused) is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, from the viewpoint of maintaining an etching rate at or below a certain level, and is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less, from the viewpoint of maintaining an etching rate at or above a certain level. More specifically, the amount of the compound having an ethyleneimine repeating unit in the etching solution used in the etching step (etching solution when reused) is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.05% by mass or more and 5% by mass or less, and even more preferably 0.1% by mass or more and 3% by mass or less. When component D contains a compound having a repeating unit derived from allylamine, the blending amount of the compound having a repeating unit derived from allylamine in the etching solution used in the etching step (the etching solution when reused) is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, from the viewpoint of keeping the etching rate at or below a certain level, and is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less, from the viewpoint of keeping the etching rate at or above a certain level.More specifically, the amount of the compound having a repeating unit derived from allylamine in the etching solution used in the etching step (the etching solution when reused) is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.05% by mass or more and 5% by mass or less, and even more preferably 0.1% by mass or more and 3% by mass or less. When component D contains a compound having a repeating unit derived from diallylamine, the amount of the compound having a repeating unit derived from diallylamine in the etching solution used in the etching step (the etching solution when reused) is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, from the viewpoint of maintaining the etching rate at a certain level or less, and is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less, from the viewpoint of maintaining the etching rate at a certain level or more. More specifically, the amount of the compound having a repeating unit derived from diallylamine in the etching solution used in the etching step (the etching solution when reused) is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.05% by mass or more and 5% by mass or less, and even more preferably 0.1% by mass or more and 10% by mass or less.

[0029] The mass ratio of component D to Group 6 element metal ions (component D / Group 6 element metal ions) in the etching solution used in the etching step (the etching solution when reused) is preferably 0.1 or more, more preferably 0.5 or more, and more preferably 1 or more, from the viewpoint of optimizing the etching rate, and from the same viewpoint, is preferably 100 or less, more preferably 50 or less, and even more preferably 10 or less.

[0030] (Component E: Nitrogen-Containing Basic Compound) In the present disclosure, component E contained in the etching solution used in the etching step (etching solution when reused) is a nitrogen-containing basic compound, and is preferably a nitrogen-containing basic compound having a molecular weight of 300 or less. However, component E does not include component D. That is, in one or more embodiments, component E does not include component D having a molecular weight of 300 or less.

[0031] From the viewpoint of suppressing variation in the etching rate between the first use and reuse of the etching solution, the molecular weight of component E is preferably 300 or less, more preferably less than 300, even more preferably 250 or less, and even more preferably 200 or less, and from the same viewpoint, it is preferably 15 or more, more preferably 20 or more, and even more preferably 30 or more. More specifically, the molecular weight of component E is preferably 15 or more and 300 or less, more preferably 15 or more and less than 300, even more preferably 20 or more and 250 or less, and even more preferably 30 or more and 200 or less.

[0032] In one or more embodiments, from the viewpoint of suppressing variation in etching rate between initial use and reuse of the etching solution, Component E is preferably at least one selected from ammonia, alkylamines, alkanolamines, alicyclic amines, aromatic amines, and polyalkylene polyamines, more preferably at least one selected from ammonia, alicyclic amines, and polyalkylene polyamines, and even more preferably contains polyalkylene polyamines. The content of polyalkylene polyamine in Component E is preferably 10% by mass or more, more preferably 50% by mass or more, and even more preferably 100% by mass. Examples of the alkyl amines include ethylamine. Examples of the alkanol amines include 2-(2-aminoethylamino)ethanol. Examples of the alicyclic amines include N-(2-hydroxyethyl)piperazine and N-(2-aminoethyl)piperazine. Examples of the aromatic amines include benzotriazole, aminopyrazole, aminopyridine, aminopyrimidine, aminopyrazine, aminooxazole, and thiazole amine. From the same viewpoint, the polyalkylene polyamine is preferably a polyalkylene polyamine having 2 to 4 amino groups in the molecule, and more preferably at least one selected from alkylene diamines, dialkylene triamines, and trialkylene tetramines. Examples of the alkylene diamines include ethylene diamine. Examples of the dialkylene triamines include diethylene triamine. Examples of the trialkylene tetramines include triethylene tetramine. Component E may be used alone or in combination of two or more.

[0033] The amount of component E in the etching solution used in the etching step (the etching solution when reused) is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, even more preferably 0.4% by mass or more, even more preferably 0.8% by mass or more, and even more preferably 1.2% by mass or more, from the viewpoint of suppressing variation in the etching rate between the first use and reuse of the etching solution. Furthermore, from the viewpoint of the liquid permeability during filtration due to the solution viscosity, it is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less. More specifically, the amount of component E in the etching solution used in the etching step is preferably 0.005% by mass or more and 20% by mass or less, or 0.01% by mass or more and 20% by mass or less, or preferably 0.4% by mass or more and 20% by mass or less, more preferably 0.8% by mass or more and 15% by mass or less, and even more preferably 1.2% by mass or more and 10% by mass or less. When component E is a combination of two or more types, the amount of component E is the total amount thereof. When component E contains a polyalkylene polyamine, the amount of polyalkylene polyamine in the etching solution used in the etching step (the etching solution when reused) is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, even more preferably 0.4% by mass or more, even more preferably 0.8% by mass or more, and even more preferably 1.2% by mass or more, from the viewpoint of suppressing variation in the etching rate between the first use and reuse of the etching solution, and is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, from the viewpoint of the liquid permeability during filtration due to the solution viscosity. More specifically, the amount of polyalkylene polyamine in the etching solution used in the etching step is preferably 0.005% by mass or more and 20% by mass or less, or 0.01% by mass or more and 20% by mass or less, or preferably 0.4% by mass or more and 20% by mass or less, more preferably 0.8% by mass or more and 15% by mass or less, and even more preferably 1.2% by mass or more and 10% by mass or less.

[0034] The mass ratio of component D to component E (component D / component E) in the etching solution used in the etching step (etching solution when reused) is preferably 0.01 or more, more preferably 0.02 or more, even more preferably 0.05 or more, and still more preferably 0.1 or more, from the viewpoint of optimizing the etching rate, and from the same viewpoint, is preferably 100 or less, more preferably 80 or less, even more preferably 50 or less, and still more preferably 10 or less. More specifically, the mass ratio (component D / component E) is preferably 0.01 or more and 100 or less, more preferably 0.02 or more and 80 or less, even more preferably 0.05 or more and 50 or less, and still more preferably 0.1 or more and 10 or less.

[0035] The mass ratio of component E to Group 6 element metal ions (component E / Group 6 element metal ions) in the etching solution used in the etching step (etching solution when reused) is, from the viewpoint of optimizing the etching rate, 1 or more, preferably 5 or more, more preferably 10 or more, and from the same viewpoint, preferably 100,000 or less, more preferably 50,000 or less, and even more preferably 10,000 or less. More specifically, the mass ratio (component E / Group 6 element metal ions) is preferably 1 or more and 100,000 or less, more preferably 5 or more and 50,000 or less, and even more preferably 10 or more and 10,000 or less.

[0036] (Component F: Organic Acid) In one or more embodiments, the etching solution used in the etching step (etching solution when reused) may further contain an organic acid (hereinafter also referred to as "component F"). Examples of the organic acid include at least one selected from formic acid, acetic acid, methoxyacetic acid, ethoxyacetic acid, propionic acid, butyric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, fumaric acid, phthalic acid, trimellitic acid, hydroxyacetic acid, lactic acid, salicylic acid, malic acid, tartaric acid, citric acid, aspartic acid, and glutamic acid. From the viewpoint of uniform etching of the layer to be etched, the organic acid is preferably a monovalent organic acid having 1 to 10 carbon atoms, more preferably a monovalent carboxylic acid having 1 to 10 carbon atoms, and even more preferably one containing acetic acid. The content of acetic acid in component F is preferably 10% by mass or more, more preferably 50% by mass or more, and even more preferably 100% by mass. The organic acids may be used alone or in combination of two or more.

[0037] The amount of organic acid (component F) in the etching solution used in the etching step (the etching solution when reused) is preferably 2% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, from the viewpoint of uniform etching of the layer to be etched, and from the same viewpoint, is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less. More specifically, the amount of organic acid (component F) in the etching solution used in the etching step is preferably 2% by mass or more and 60% by mass or less, more preferably 3% by mass or more and 50% by mass or less, and even more preferably 5% by mass or more and 40% by mass or less. When two or more organic acids are used in combination, the amount of the organic acids is the total amount of the organic acids. When component F contains acetic acid, the amount of acetic acid in the etching solution used in the etching step (the etching solution when reused) is preferably 2% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more from the viewpoint of uniform etching of the layer to be etched, and from the same viewpoint, is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less. More specifically, the amount of acetic acid in the etching solution used in the etching step is preferably 2% by mass or more and 60% by mass or less, more preferably 3% by mass or more and 50% by mass or less, and even more preferably 5% by mass or more and 40% by mass or less.

[0038] The total amount of phosphoric acid (component A), nitric acid (component B), and organic acid (component F) in the etching solution used in the etching step (the etching solution when reused) is preferably 70% by mass or more, more preferably 75% by mass or more, and even more preferably 80% by mass or more, from the viewpoint of uniform etching of the layer to be etched. From the same viewpoint, it is preferably 99.9% by mass or less, more preferably 99% by mass or less, and even more preferably 98% by mass or less. The total amount of phosphoric acid, nitric acid, and organic acid in the etching solution used in the etching step is preferably 70% by mass or more and 99.9% by mass or less, more preferably 75% by mass or more and 99% by mass or less, and even more preferably 80% by mass or more and 98% by mass or less. When the organic acid contains acetic acid, the total amount of phosphoric acid, nitric acid, and acetic acid in the etching solution used in the etching step is preferably in the same range as the total amount of phosphoric acid, nitric acid, and organic acid.

[0039] In one or more embodiments, the acid contained in the etching solution used in the etching step (the etching solution when reused) is an acid containing phosphoric acid, nitric acid, and an organic acid, and from the viewpoint of improving the etching rate, it is preferably an acid containing phosphoric acid, nitric acid, and acetic acid, and more preferably a mixed acid consisting of phosphoric acid, nitric acid, and acetic acid. In one or more embodiments, the "mixed acid" in the present disclosure is a mixed acid containing phosphoric acid and nitric acid, in one or more other embodiments, a mixed acid containing phosphoric acid, nitric acid, and an organic acid, in one or more other embodiments, a mixed acid containing phosphoric acid, nitric acid, and acetic acid, and in one or more other embodiments, a mixed acid consisting of phosphoric acid, nitric acid, and acetic acid.

[0040] (Other Components) The etching solution used in the etching step (the etching solution when reused) may further contain other components within the range that does not impair the effects of the present disclosure. Examples of other components include inorganic acids other than phosphoric acid and nitric acid, chelating agents, surfactants, solubilizing agents, preservatives, rust inhibitors, disinfectants, antibacterial agents, antioxidants, etc.

[0041] In one or more embodiments, the etching solution used before etching in the etching method of the present disclosure, i.e., the first etching solution used (hereinafter also referred to as the "first-use etching solution"), can be obtained by blending component A, component B, component C, component D, component E, and, if desired, the optional components described above (component F, other components) by a known method, and is an etching solution that does not contain Group 6 element metal ions. Therefore, in one or more embodiments, the method for producing the first-use etching solution can include a step of blending at least component A, component B, component C, component D, and component E. In one or more embodiments, the reused etching solution used in the etching step of the etching method of the present disclosure is obtained by using the first-use etching solution once or multiple times for etching. That is, in one or more embodiments, the reused etching solution is obtained by blending component A, component B, component C, component D, and component E, and contains Group 6 element metal ions. Therefore, in another aspect, the present disclosure relates to an etching method including a step of etching a layer to be etched containing a Group 6 element metal with an etching solution, wherein the etching solution is a blend of components A, B, C, D, and E, and contains Group 6 element metal ions, the content of the Group 6 element metal ions in the etching solution is 0.005 mass% or more, and the mass ratio of component E to the Group 6 element metal ions (component E / Group 6 element metal ions) is 1 or more. In one or more embodiments, the phrase "blending at least components A, B, C, D, and E" in the present disclosure includes simultaneously or sequentially mixing components A, B, C, D, and E, and, if necessary, the optional components described above (component F, other components). The order of mixing is not particularly limited. The blending can be performed using a mixer such as a propeller-type agitator, a pump for liquid circulation agitation, a homomixer, a homogenizer, an ultrasonic disperser, or a wet ball mill. The preferred blending amounts of each component in the method for producing the etching solution for the first use can be the same as the preferred blending amounts of each component in the etching solution for reuse described above.

[0042] In the present disclosure, the "amount of each component of the etching solution" refers, in one or more embodiments, to the amount of each component used in the etching step, i.e., the amount of each component in the etching solution at the time of starting use in the etching process (at the time of use). In one or more embodiments, the amount of each component in the etching solution used in the etching step can be considered to be the content of each component in the etching solution used in the etching step. However, if there is an effect of neutralization, the amount of each component may differ from the content.

[0043] The etching solution for first use may be a so-called one-component type, in which all components are premixed and supplied to the market, or a so-called two-component type, in which components are mixed at the time of use. Examples of two-component etching solutions include those in which water is separated into a first component and a second component, and components A, B, C, D, and E are contained in either or both of the first and second components, and the first and second components are mixed at the time of use. The first and second components may each contain the optional components described above (organic acids, other components) as necessary.

[0044] From the viewpoint of uniform etching of the layer to be etched, the pH of the etching solution when used for the first time and when reused is preferably 1 or less, more preferably 0 or less, even more preferably less than 0, and even more preferably about -1. The pH of the etching solution when used for the first time and when reused can be preferably -5 or more, more preferably -3 or more. In the present disclosure, the pH of the etching solution is a value at 25°C and can be measured using a pH meter, specifically, by the method described in the examples.

[0045] The etching solution for initial use may be stored and supplied in a concentrated state as long as its storage stability is not impaired. This is preferable because it reduces production and transportation costs. The concentrated solution can then be diluted appropriately with water or an aqueous acid solution as needed for use in the etching process. The dilution ratio can be, for example, 3 to 100 times.

[0046] In one or more embodiments, the etching method of the present disclosure may further include, prior to the etching step, a step of measuring the concentration of a Group 6 element metal in the etching solution used in the etching step.

[0047] In one or more embodiments, the etching method of the present disclosure can be used to etch metals in the manufacturing process of electronic devices, particularly semiconductor wafers. In one or more embodiments, the etching method of the present disclosure can be suitably used in the manufacture of semiconductor wafers. This improves uniform etching of the layer to be etched, thereby improving productivity and yield. In one or more embodiments, the etching method of the present disclosure can be used to etch electrodes in the manufacturing process of electronic devices, particularly semiconductor memories such as nonvolatile memories including NAND flash memories. In one or more embodiments, the etching method of the present disclosure can be suitably used to manufacture patterns having three-dimensional structures. This allows for the production of advanced devices such as large-capacity memories. The etching method of the present disclosure can be used, for example, in etching methods such as those disclosed in JP 2020-145412 A.

[0048] The present disclosure further relates to one or more of the following embodiments: <1> An etching method including a step of etching a layer to be etched that contains a Group 6 element metal with an etching solution, wherein the etching solution contains the following components A, B, C, D, and E, and Group 6 element metal ions, wherein the content of the Group 6 element metal ions in the etching solution is 0.005 mass% or more, and the mass ratio of component E to the Group 6 element metal ions (component E / Group 6 element metal ions) is 1 or more. Component A: phosphoric acid; component B: nitric acid; component C: water; component D: polyamine having an average molecular weight of 300 or more; component E: nitrogen-containing basic compound (excluding component D). <2> The etching method according to <1>, wherein the molecular weight of component E is 300 or less. <3> The etching method according to <1> or <2>, wherein the mass ratio of component E to Group 6 element metal ions (component E / Group 6 element metal ions) in the etching solution is 1 or more, or 5 or more, or 10 or more, and 100,000 or less, or 50,000 or less, or 10,000 or less. <4> The etching method according to any one of <1> to <3>, wherein the Group 6 element metal is at least one selected from tungsten and molybdenum. <5> The etching method according to any one of <1> to <4>, wherein the blending amount of component A in the etching solution is 40 mass% or more, or 50 mass% or more, or 60 mass% or more, and 90 mass% or less, or 85 mass% or less, or 80 mass% or less. <6> The etching method according to any one of <1> to <5>, wherein the blending amount of component B in the etching solution is 0.5% by mass or more, or 1% by mass or more, or 1.5% by mass or more, and 20% by mass or less, or 10% by mass or less, or 8% by mass or less. <7> The etching method according to any one of <1> to <6>, wherein the blending amount of component C in the etching solution is 2% by mass or more, or 5% by mass or more, or 7% by mass or more, and 30% by mass or less, or 25% by mass or less, or 20% by mass or less.<8> The etching method according to any one of <1> to <7>, wherein the blending amount of component D in the etching solution is 0.01% by mass or more, or 0.05% by mass or more, or 0.1% by mass or more, and 10% by mass or less, or 5% by mass or less, or 3% by mass or less. <9> The etching method according to any one of <1> to <8>, wherein the blending amount of component E in the etching solution is 0.005% by mass or more, or 0.01% by mass or more, or 0.4% by mass or more, or 0.8% by mass or more, or 1.2% by mass or more, and 20% by mass or less, or 15% by mass or less, or 10% by mass or less. <10> The etching method according to any one of <1> to <9>, wherein the content of Group 6 element metal ions in the etching solution is 1% by mass or less. <11> The etching method according to any one of <1> to <10>, wherein the mass ratio of component D to Group 6 element metal ions (component D / Group 6 element metal ions) in the etching solution is 0.1 or more, or 0.5 or more, or 1 or more, and 100 or less, or 50 or less, or 10 or less. <12> The etching method according to any one of <1> to <11>, wherein the mass ratio of component A to Group 6 element metal ions (component A / Group 6 element metal ions) in the etching solution is 10 or more, or 50 or more, or 100 or more, and 10,000 or less, or 5,000 or less, or 1,000 or less. <13> The etching method according to any one of <1> to <12>, wherein the mass ratio of component B to Group 6 element metal ions (component B / Group 6 element metal ions) in the etching solution is 1 or more, or 5 or more, or 10 or more, and 1000 or less, or 500 or less, or 300 or less, or 100 or less. <14> The etching method according to any one of <1> to <13>, wherein the mass ratio of component D to component E (component D / component E) in the etching solution is 0.01 or more, or 0.02 or more, or 0.05 or more, or 0.1 or more, and 100 or less, or 80 or less, or 50 or less, or 10 or less.<15> An etching method including a step of etching a layer to be etched that contains a Group 6 element metal with an etching solution, wherein the etching solution is a blend of the following components A, B, C, D, and E, and contains a Group 6 element metal ion, wherein the content of the Group 6 element metal ion in the etching solution is 0.005 mass% or more, and the mass ratio of component E to the Group 6 element metal ion (component E / Group 6 element metal ion) is 1 or more: component A: phosphoric acid; component B: nitric acid; component C: water; component D: a polyvalent amine having an average molecular weight of 300 or more; and component E: a nitrogen-containing basic compound (excluding component D).

[0049] The present disclosure will be specifically described below using examples, but the present disclosure is not limited to these examples in any way.

[0050] 1. Preparation of Etching Solutions (Examples 1 to 3, Comparative Examples 1 to 4) Mixed acid (phosphoric acid / acetic acid / nitric acid, mass ratio: 75 / 7 / 3), water (component C), polyamine (component D), and nitrogen-containing basic compound (component E) were blended, and molybdenum (Mo) powder was added. The mixture was thoroughly dissolved at 60°C until transparent, to obtain etching solutions (pH: -1) of Examples 1 to 3 and Comparative Examples 1 to 4. The etching solutions of Examples 1 to 3 and Comparative Examples 1 to 4 were molybdenum-containing etching solutions intended for reuse. The amount of Mo dissolved (mass %) in the etching solutions was as shown in Table 1. (Reference Examples 1 and 2) Mixed acid (phosphoric acid / acetic acid / nitric acid, mass ratio: 75 / 7 / 3), water (component C), polyamine (component D), and nitrogen-containing basic compound (component E) were blended to obtain etching solutions (pH: -1) of Reference Examples 1 and 2. The etching solutions of Reference Examples 1 and 2 were molybdenum-free etching solutions intended for initial use. The amounts (mass %, active content) of the components in each of the etching solutions prepared as described above are shown in Table 1. The mass ratios of the mixed acids are calculated by mass, and the amount of water included includes the amount of water contained in the acid aqueous solution, etc.

[0051] The following components were used to prepare the etching solution: Phosphoric acid [manufactured by Rinkagaku Kogyo Co., Ltd., concentration 85%] Nitric acid [Fujifilm Wako Pure Chemical Industries, Ltd., concentration 70%] Acetic acid [Fujifilm Wako Pure Chemical Industries, Ltd., concentration 100%] PEI: polyethyleneimine [number average molecular weight 1,800, "Epomin SP-018" manufactured by Nippon Shokubai Co., Ltd.] TETA: triethylenetetramine [molecular weight 146.23, Fujifilm Wako Pure Chemical Industries, Ltd.] Water [ultrapure water produced using a continuous pure water production system (PureConti PC-2000VRL type) and a subsystem (Macace KC-05H type) manufactured by Kurita Water Industries Ltd.] Molybdenum powder ["Mo-3K" manufactured by Japan New Metals Co., Ltd.]

[0052] 2. Measurement of pH of etching solution The pH value of the etching solution at 25°C was measured using a pH meter (manufactured by DKK-Toa Corporation), and was the value measured one minute after the electrode of the pH meter was immersed in the etching solution.

[0053] 3. Evaluation of Etching Solution [Evaluation of Etching Rate of Molybdenum Plate] A molybdenum plate, 2 cm long, 2 cm wide, and 0.1 mm thick, whose weight had been measured in advance, was immersed in the etching solution prepared with each composition, and the molybdenum plate was etched at 40°C for 30 minutes. After washing with water, the molybdenum plate was again weighed, and the difference was taken as the amount of etching. A precision balance was used to measure the weight. The etching rate was then calculated using the following formula: Etching rate (nm / min) = Etching amount (g) × 10 7 / (10.28 (g / cm 3 ) x 2 x 2) / etching time (minutes) / 2

[0054]

[0055] As shown in Table 1, when the amount of dissolved Mo was 0.005 mass% or more, the etching rate increased in the absence of component E (Comparative Examples 3 and 4). Examples 1 and 2, in which the mass ratio of component E to Mo was 1 or more, had etching rates comparable to Reference Example 1, in which Mo was not dissolved, even when the amount of dissolved Mo was 0.1 mass% and 0.5 mass%, respectively, and the increase in etching rate was suppressed. Comparative Example 1, in which the amount of dissolved Mo was 0.1 mass% and the mass ratio of component E to Mo was 0.1, and Comparative Example 2, in which the amount of dissolved Mo was 0.5 mass% and the mass ratio of component E to Mo was 0.02, showed significantly higher etching rates than Reference Example 2, in which Mo was not dissolved, which simulates an etching solution used for the first time. Example 3, in which the amount of dissolved Mo was 0.009 mass% and the mass ratio of component E to Mo was 1.11, showed etching rates comparable to Reference Example 2, and the increase in etching rate was suppressed. Therefore, it was found that by using an etching solution in which the content of Group 6 element metal such as Mo is 0.005 mass % or more and the mass ratio of component E to Group 6 element metal is 1 or more, the etching rate can be maintained, that is, the variation in rate between the etching rate when the etching solution is used for the first time (Reference Examples 1 and 2) and the etching rate when the etching solution is reused (Examples 1 to 3) can be suppressed.

[0056] The etching method of the present disclosure can maintain the etching rate even when reused, and is therefore useful in manufacturing methods for large-capacity semiconductor memories.

Claims

1. An etching method comprising a step of etching a layer to be etched containing a Group 6 element metal with an etching solution, wherein the etching solution contains the following components A, B, C, D, and E, and Group 6 element metal ions, wherein the content of the Group 6 element metal ions in the etching solution is 0.005 mass% or more, and the mass ratio of component E to the Group 6 element metal ions (component E / Group 6 element metal ions) is 1 or more: component A: phosphoric acid; component B: nitric acid; component C: water; component D: polyvalent amine having an average molecular weight of 300 or more; component E: nitrogen-containing basic compound (excluding component D).

2. The etching method according to claim 1, wherein the molecular weight of component E is 300 or less.

3. The etching method according to claim 1 or 2, wherein the mass ratio of component E to Group 6 element metal ions in the etching solution (component E / Group 6 element metal ions) is 10,000 or less.

4. The etching method according to any one of claims 1 to 3, wherein the Group 6 element metal is at least one selected from tungsten and molybdenum.

5. An etching method according to any one of claims 1 to 4, wherein the amount of component D in the etching solution is 0.01 mass % or more and 10 mass % or less.

6. The etching method according to any one of claims 1 to 5, wherein the content of Group 6 element metal ions in the etching solution is 1 mass % or less.

7. The etching method according to any one of claims 1 to 6, wherein the mass ratio of component D to Group 6 element metal ions in the etching solution (component D / Group 6 element metal ions) is 100 or less.

8. An etching method according to any one of claims 1 to 7, wherein the mass ratio of component A to Group 6 element metal ions in the etching solution (component A / Group 6 element metal ions) is 10,000 or less.

9. The etching method according to any one of claims 1 to 8, wherein the mass ratio of component B to Group 6 element metal ions in the etching solution (component B / Group 6 element metal ions) is 1,000 or less.

10. An etching method according to any one of claims 1 to 9, wherein the mass ratio of component D to component E in the etching solution (component D / component E) is 100 or less.

11. An etching method comprising a step of etching a layer to be etched containing a Group 6 element metal with an etching solution, wherein the etching solution is a blend of the following components A, B, C, D, and E, and contains Group 6 element metal ions, wherein the content of the Group 6 element metal ions in the etching solution is 0.005 mass% or more, and the mass ratio of component E to the Group 6 element metal ions (component E / Group 6 element metal ions) is 1 or more: component A: phosphoric acid component B: nitric acid component C: water component D: polyvalent amine having an average molecular weight of 300 or more component E: nitrogen-containing basic compound (excluding component D)

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