JP7685685B1 - Etching solution - Google Patents

Abstract

In one aspect, there is provided an etching solution that has excellent storage stability, suppresses etching, and improves the quality of the surface of a layer to be etched after etching.
[Solution] In one aspect, the present disclosure relates to an etching solution for etching a layer to be etched that contains at least one type of metal, the etching solution being composed of a nitrogen-containing compound having a ratio C/N of the number of carbon atoms (C) to the number of nitrogen atoms (N) in one molecule of 2.2 or more, an organic acid, an acid including nitric acid and phosphoric acid, and water, wherein the amount of the organic acid in the etching solution is 50 mass% or more.
[Selection diagram] None

Description

This disclosure relates to an etching solution and an etching method using the same.

In the manufacturing process of a semiconductor device, a process is carried out in which a layer to be etched, which contains 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 and processed into a predetermined pattern shape.
In recent years, the semiconductor field has seen an increase in integration density, which has led to a demand for more complex and finer wiring. This has resulted in increased demands for pattern processing techniques and etching solutions, and various etching methods and etching solutions have been proposed (Patent Documents 1 to 3).

For example, Patent Document 1 proposes an etching solution containing phosphoric acid, nitric acid, and a polyalkylene polyamine containing three or more amino groups in one molecule, which is used for etching a metal film having at least one layer of a metal thin film made of molybdenum or a molybdenum alloy.
Patent Document 2 proposes a substrate processing method including the steps of: supplying a first etching solution containing an oxidant (e.g., nitric acid), a catalyst (e.g., phosphoric acid), and a moisture regulator (e.g., an organic acid), in which the proportion of the moisture regulator is greater than the combined proportion of the oxidant and the catalyst, to a substrate having a laminated film including a molybdenum film; and, after supplying the first etching solution to the substrate, supplying a second etching solution to the substrate, in which the proportion of the moisture regulator is greater than that of the first etching solution.
Patent Document 3 proposes an etching solution for selectively etching aluminum oxide, tungsten and/or titanium nitride, which contains about 65 to 90% by weight of phosphoric acid, about 0.01 to 4% by weight of acetic acid, 0.01 to 5% by weight of nitric acid, and water.

JP 2013-237873 A Patent Publication No. 2021-114569 Special Publication No. 2022-502835

As an etching solution, a mixed acid aqueous solution (strong acid aqueous solution) containing phosphoric acid, nitric acid, and an organic acid (e.g., acetic acid) is generally used. In addition, a nitrogen-containing compound may be used as an etching inhibitor in the etching solution for reasons such as not impairing the quality of the etched layer surface (metal film surface) after etching. Patent Document 1 proposes adding polyalkylene polyamine to an etching solution that does not contain acetic acid as an essential component, but adding an auxiliary such as polyalkylene polyamine to the mixed acid aqueous solution causes turbidity and deteriorates the storage stability of the etching solution.

Therefore, in one aspect, the present disclosure provides an etching solution that has excellent storage stability, suppresses etching, and improves the quality of the surface of the layer to be etched after etching, and an etching method using the same.

In one aspect, the present disclosure relates to an etching solution for etching a layer to be etched that contains at least one metal, the etching solution being made by blending a nitrogen-containing compound having a ratio C/N of the number of carbon atoms (C) to the number of nitrogen atoms (N) in one molecule of 2.2 or more, an organic acid, and an acid containing nitric acid and phosphoric acid, the amount of organic acid blended in the etching solution being 50 mass% or more.

In one aspect, the present disclosure relates to an etching method that includes a step of etching a layer to be etched that contains at least one metal using the etching solution of the present disclosure, and the temperature of the etching solution during etching is 20°C or higher and 50°C or lower.

In one aspect, the present disclosure relates to an etching solution for etching a layer to be etched that contains at least one metal, the etching solution containing a salt of a nitrogen-containing compound having a ratio C/N of the number of carbon atoms (C) to the number of nitrogen atoms (N) in one molecule of 2.2 or more, an organic acid, and an acid containing nitric acid and phosphoric acid, the amount of organic acid in the etching solution being 50 mass% or more.

In one aspect, the present disclosure relates to an etching solution for etching a layer to be etched that contains at least one metal, the etching solution being made by blending a nitrogen-containing compound having a ratio C/N of the number of carbon atoms (C) to the number of nitrogen atoms (N) in one molecule of 2.2 or more, an organic acid, and an acid containing nitric acid and phosphoric acid, the amount of organic acid in the etching solution being 80 mass % or more.

In one aspect, the present disclosure relates to an etching solution for etching a layer to be etched that contains molybdenum, the etching solution being made by blending at least one nitrogen-containing compound having a ratio C/N of the number of carbon atoms (C) to the number of nitrogen atoms (N) in one molecule of 2.2 or more, an organic acid, and an acid including nitric acid and phosphoric acid, and the amount of the organic acid in the etching solution is 50 mass% or more.

In one aspect, the present disclosure relates to a method for manufacturing an electronic component, comprising the step of etching an etched layer containing at least one metal using the etching solution of the present disclosure.

According to one aspect of the present disclosure, it is possible to provide an etching solution that has excellent storage stability, suppresses etching, and improves the quality of the surface of the layer to be etched after etching.

As a result of intensive research, the inventors have found that by using an etching solution that contains or is a combination of a specific nitrogen-containing compound and an acid containing 50% by mass or more of an organic acid, it is possible to suppress etching and improve the quality of the surface of the layer to be etched after etching (uniform etching of the layer to be etched), while also improving storage stability.

In one aspect, the present disclosure relates to an etching solution for etching a layer to be etched that contains at least one metal, the etching solution being composed of a nitrogen-containing compound having a ratio C/N of the number of carbon atoms (C) to the number of nitrogen atoms (N) in one molecule of 2.2 or more, an organic acid, and an acid containing nitric acid and phosphoric acid, the amount of organic acid in the etching solution being 50 mass% or more (hereinafter also referred to as the "etching solution of the present disclosure").

Although the details of the mechanism by which the effects of the present disclosure are manifested are not clear, it is presumed as follows.
When a nitrogen-containing compound such as a polyvalent amine is mixed as an etching inhibitor with a mixed acid solution (strong acid solution) containing phosphoric acid, nitric acid, and an organic acid (e.g., acetic acid), which is generally used as an etching solution, the polyvalent amine can form a salt with the acid in the mixed acid solution. In particular, for example, in the case of a polyvalent amine containing many nitrogen atoms, which are hydrophilic groups, in the molecule, the salt of the hydrophilic polyvalent amine and the acid is easily dissolved in an aqueous solvent. In the case of a polyvalent amine containing many methylene groups, which are hydrophobic groups, in the molecule, the salt of the hydrophobic polyvalent amine and the acid is difficult to dissolve in an aqueous solvent.
On the other hand, in a low pH mixed acid solution (strongly acidic aqueous solution), the organic acid does not dissociate, and as the amount of organic acid increases, the hydrophobicity of the mixed acid solution increases. Therefore, while salts of hydrophobic polyamines and acids can be dissolved, the solubility of salts of hydrophilic polyamines and acids is extremely reduced, causing the solution to become cloudy.
In the present disclosure, a specific nitrogen-containing compound having high hydrophobicity or amphiphilicity (a nitrogen-containing compound having a ratio C/N of the number of carbon atoms (C) to the number of nitrogen atoms (N) in one molecule of 2.2 or more) is used as an etching inhibitor, and this nitrogen-containing compound is combined with a mixed acid containing 50 mass % or more of an organic acid, which is believed to improve the solubility of a salt of the nitrogen-containing compound and an acid, and thereby improve the storage stability of the etching solution.
It is also known that the nitrogen-containing compound used as an etching inhibitor acts on the metal surface and inhibits etching by acid. In the present disclosure, it is believed that the high concentration of organic acid reduces the viscosity of the mixed acid aqueous solution, improving the diffusivity of the acid itself and the nitrogen-containing compound, thereby achieving uniform etching of the surface, that is, inhibiting etching and improving the quality of the surface of the etched layer after etching.
However, the present disclosure need not be construed as being limited to these mechanisms.

[Nitrogen-containing compound (component A) having a ratio C/N of the number of carbon atoms (C) to the number of nitrogen atoms (N) in one molecule of 2.2 or more]
The etching solution of the present disclosure contains or is formulated with a nitrogen-containing compound (hereinafter also referred to as "component A") having a ratio C/N of the number of carbon atoms (C) to the number of nitrogen atoms (N) in one molecule of 2.2 or more.
From the viewpoints of storage stability and etching inhibition, the number of carbon atoms (C) in one molecule of component A is preferably 4 or more, and more preferably 8 or more, and from the viewpoint of improving the quality of the etched layer, the number of carbon atoms is preferably 24 or less, and more preferably 18 or less. From the same viewpoint, the number of carbon atoms in one molecule of component A is preferably 4 or more and 24 or less, and more preferably 8 or more and 18 or less.
From the viewpoints of storage stability and etching inhibition, the number of nitrogen atoms (N) in one molecule of component A is preferably 1 or more, more preferably 2 or more, and from the viewpoint of improving the quality of the etched layer, preferably 3 or less. From the same viewpoint, the number of nitrogen atoms in one molecule of component A is preferably 1 or more and 3 or less.
In one or more embodiments, the ratio C/N of the number of carbon atoms (C) to the number of nitrogen atoms (N) in one molecule of component A is 2.2 or more, preferably 2.3 or more, more preferably 4 or more, and even more preferably 8 or more, from the viewpoint of storage stability and etching inhibition, and from the viewpoint of improving the quality of the etched layer, is preferably 20 or less, more preferably 18 or less. More specifically, the ratio C/N of component A is preferably 2.2 or more and 20 or less, more preferably 4 or more and 18 or less, and even more preferably 8 or more and 18 or less.
In one or a plurality of embodiments, component A contained or blended in the etching solution of the present disclosure is at least one nitrogen-containing compound selected from aliphatic amines, aromatic amines, and aminoalcohols.
Component A may be one type or a combination of two or more types.

In one or more embodiments, Component A may be in the form of a salt of the nitrogen-containing compound. In one or more embodiments, Component A may form a salt with an acid in the etching solution.
Thus, in another aspect, the present disclosure relates to an etching solution for etching a layer to be etched that contains at least one metal, the etching solution containing a salt of component A and an acid that contains an organic acid, nitric acid, and phosphoric acid, the amount of the organic acid in the etching solution being 50 mass% or more.

上記式（Ｉ）中、Ｒ¹は、炭素数１以上１８以下の直鎖あるいは分岐鎖のアルキル基、炭素数１以上１８以下の直鎖あるいは分岐鎖のアルケニル基、又は、炭素数１以上１８以下の環状炭化水素基であり、前記アルキル基、前記アルケニル基及び前記環状炭化水素基は、アミノ基、又は、エーテル結合を含んでいてもよい。
Ｒ²及びＲ³はそれぞれ独立して、水素原子、炭素数１以上８以下の直鎖あるいは分岐鎖のアルキル基、炭素数１以上８以下の直鎖あるいは分岐鎖のアルケニル基、又は、炭素数が１以上８以下の環状炭化水素基であり、前記アルキル基、前記アルケニル基及び前記環状炭化水素基は、アミノ基、又は、エーテル結合を含んでいてもよい。
上記式（Ｉ）中、エッチング抑制及び被エッチング層の品質向上の観点から、Ｒ¹は、炭素数１以上１８以下の直鎖アルキル基、アミノ基を有する炭素数１以上１８以上の直鎖アルキル基、又は、炭素数１以上１８以下の分岐鎖のアルケニル基が好ましく挙げられる。Ｒ²及びＲ³はそれぞれ独立して、水素原子、メチル基、又は、アミノ基を有する炭素数１以上８以下の直鎖のアルキル基が好ましく挙げられる。 (Aliphatic amines)
In one or more embodiments, component A may be an aliphatic amine. Examples of the aliphatic amine include primary, secondary, or tertiary aliphatic amines. The aliphatic amine may be one type or a combination of two or more types.
In the present disclosure, a primary, secondary or tertiary aliphatic amine is a compound in which at least one hydrogen atom of ammonia (NH ₃ ) is substituted with a hydrocarbon group. In one or more embodiments, a primary aliphatic amine is a compound in which one hydrogen atom of ammonia is substituted with a hydrocarbon group, a secondary aliphatic amine is a compound in which two hydrogen atoms of ammonia are substituted with hydrocarbon groups, and a tertiary aliphatic amine is a compound in which three hydrogen atoms of ammonia are substituted with hydrocarbon groups. Examples of the hydrocarbon group include a hydrocarbon group having 1 to 24 carbon atoms. The hydrocarbon group may be linear, branched or cyclic. The hydrocarbon group may include an unsaturated bond. The hydrocarbon group may be a group partially substituted with an oxygen atom or the like.
From the viewpoints of storage stability and etching inhibition, the carbon number of the aliphatic amine is preferably 4 or more, more preferably 8 or more, and from the viewpoint of improving the quality of the etched layer, the carbon number is preferably 24 or less, more preferably 18 or less. From the same viewpoint, the carbon number of the primary, secondary or tertiary aliphatic amine is preferably 4 or more and 24 or less, more preferably 8 or more and 18 or less.
From the viewpoint of storage stability, the ratio C/N of the number of carbon atoms (C) to the number of nitrogen atoms (N) in one molecule of the aliphatic amine is preferably 4 or more, and more preferably 6 or more, and from the viewpoint of improving the quality of the etched layer, it is preferably 24 or less, more preferably 20 or less, and even more preferably 18 or less. From the same viewpoint, the ratio C/N of the number of carbon atoms to the number of nitrogen atoms in one molecule of the aliphatic amine is preferably 4 or more and 24 or less, more preferably 6 or more and 20 or less, and even more preferably 6 or more and 18 or less.
Examples of the primary aliphatic amines include oleylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, 2-ethylhexylamine, nonylamine, aminodecane, aminoundecane, aminododecane (dodecylamine), aminotridecane, tetradecylamine, aminopentadecane, hexadecylamine, aminoheptadecane, stearylamine (octadecylamine), aminononadecane, and 2-ethylhexylamine.
Examples of the secondary aliphatic amine include methylhexylamine, methylpentylamine, methyloctylamine, methylnonylamine, methyldecylamine, methylundecylamine, methyldodecylamine, methyloctadecylamine, cyclohexylamine, bis(hexamethylene)triamine, and N-butylethylenediamine.
Examples of the tertiary aliphatic amine include dimethylbutylamine, dimethylpentylamine, dimethylhexylamine, methylpentylamine, methyloctylamine, methylnonylamine, methyldecylamine, methylundecylamine, methyldodecylamine, and dimethyloctadecylamine.
In one or more embodiments, the aliphatic amine may be one or more compounds represented by the following formula (I):

In the above formula (I), R ¹ is a linear or branched alkyl group having from 1 to 18 carbon atoms, a linear or branched alkenyl group having from 1 to 18 carbon atoms, or a cyclic hydrocarbon group having from 1 to 18 carbon atoms, and the alkyl group, the alkenyl group, and the cyclic hydrocarbon group may contain an amino group or an ether bond.
^R2 and ^R3 each independently represent a hydrogen atom, a linear or branched alkyl group having from 1 to 8 carbon atoms, a linear or branched alkenyl group having from 1 to 8 carbon atoms, or a cyclic hydrocarbon group having from 1 to 8 carbon atoms, and the alkyl group, the alkenyl group, and the cyclic hydrocarbon group may contain an amino group or an ether bond.
In the above formula (I), from the viewpoint of suppressing etching and improving the quality of the etched layer, preferred examples of R ¹ include a linear alkyl group having 1 to 18 carbon atoms, a linear alkyl group having 1 to 18 carbon atoms and an amino group, or a branched alkenyl group having 1 to 18 carbon atoms. Preferred examples of R ² and R ³ each independently include a hydrogen atom, a methyl group, or a linear alkyl group having 1 to 8 carbon atoms and an amino group.

(Aromatic amines)
In one or more embodiments, Component A may be an aromatic amine. The aromatic amine may be a single type or a combination of two or more types.
In the present disclosure, an aromatic amine is a compound in which at least one hydrogen atom of ammonia (NH ₃ ) is substituted with an aromatic ring. From the viewpoint of etching suppression and improving the quality of the etched layer, the aromatic amine is preferably a primary aromatic amine in which one hydrogen atom of ammonia is substituted with an aromatic ring. An example of the aromatic ring is a benzene ring. The aromatic ring may have a substituent. An example of the substituent is an alkyl group having 1 to 12 carbon atoms. The alkyl group may be either linear or branched. An example of the branched alkyl group is an isopropyl group.
Examples of the aromatic amine, from the viewpoints of etching inhibition and storage stability, include aniline derivatives (e.g., aniline, 2,6-diisopropylaniline, etc.); triazole derivatives (e.g., benzotriazole, 5-methylbenzotriazole, etc.); imidazole derivatives; and quinoline derivatives (e.g., isoquinoline, etc.).

上記式（ＩＩ）中、Ｒ⁴は、炭素数２以上６以下の直鎖又は分岐鎖のアルキル基であり、前記アルキル基は、エーテル基を有していてもよい。
Ｒ⁵及びＲ⁶はそれぞれ独立して、水素原子、又は、炭素数２以上６以下の直鎖あるいは分岐鎖のアルキル基であり、前記アルキル基は、アミノ基、ヒドロキシ基、又はエーテル基を有していてもよい。
上記式（ＩＩ）中、エッチング抑制及び被エッチング層の品質向上の観点から、Ｒ⁴のアルキル基は直鎖であることが好ましい。同様の観点から、Ｒ⁴は、エーテル基を有する、炭素数２以上６以下の直鎖アルキル基が好ましく、Ｒ⁵及びＲ⁶はそれぞれ独立して、水素原子が好ましい。 (Amino alcohol)
In one or more embodiments, Component A may be an amino alcohol. The amino alcohol may be one type or a combination of two or more types.
In the present disclosure, an amino alcohol (alkanolamine) is a compound having a hydroxyl group and an amino group. The amino group may be a primary, secondary or tertiary amino group, and from the viewpoint of suppressing etching and improving the quality of the etched layer, a primary amino group is preferred.
The number of carbon atoms of the amino alcohol is preferably 2 or more and 24 or less, more preferably 4 or more and 18 or less, and even more preferably 4 or more and 12 or less, from the viewpoint of storage stability.
Examples of the amino alcohol include 2-(2-aminoethoxy)ethanol and triethanolamine.
In one or more embodiments, the amino alcohol (component A) may be one or more compounds represented by the following formula (II):

In the above formula (II), R ⁴ is a linear or branched alkyl group having from 2 to 6 carbon atoms, and the alkyl group may have an ether group.
^R5 and ^R6 each independently represent a hydrogen atom or a linear or branched alkyl group having from 2 to 6 carbon atoms, and the alkyl group may have an amino group, a hydroxyl group, or an ether group.
In the above formula (II), from the viewpoint of suppressing etching and improving the quality of the etched layer, the alkyl group of ^R4 is preferably linear. From the same viewpoint, ^R4 is preferably a linear alkyl group having 2 to 6 carbon atoms and an ether group, and ^R5 and ^R6 are each preferably independently a hydrogen atom.

In one or more embodiments, from the viewpoint of suppressing etching and improving the quality of the etched layer, component A is preferably at least one selected from butylamine, octylamine, dodecylamine, octadecylamine, methyloctadecylamine, dimethyloctadecylamine, oleylamine, 2-ethylhexylamine, bis(hexamethylene)triamine, aniline, 2,6-diisopropylaniline, 5-methylbenzotriazole, and 2-(2-aminoethoxy)ethanol, and more preferably at least one selected from dodecylamine, octadecylamine, methyloctadecylamine, dimethyloctadecylamine, oleylamine, bis(hexamethylene)triamine, aniline, 2,6-diisopropylaniline, 5-methylbenzotriazole, and 2-(2-aminoethoxy)ethanol.

The molecular weight of component A contained in the etching solution of the present disclosure is preferably 70 or more, more preferably 120 or more, and even more preferably 150 or more, from the viewpoint of suppressing etching and improving the quality of the layer to be etched, and is preferably 350 or less, preferably 300 or less, and even more preferably 250 or less, from the viewpoint of improving the quality of the layer to be etched. More specifically, the molecular weight of component A is preferably 70 or more and 350 or less, more preferably 120 or more and 300 or less, and even more preferably 150 or more and 250 or less.

From the viewpoint of suppressing etching and improving the quality of the layer to be etched, the amount of component A in the etching solution of the present disclosure is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.5% by mass or more, and from the viewpoint of storage stability, it is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less. From the same viewpoint, the amount of component A in the etching solution of the present disclosure is preferably 0.01% by mass or more and 5% by mass or less, more preferably 0.1% by mass or more and 3% by mass or less, and even more preferably 0.5% by mass or more and 2% by mass or less. When component A is a combination of two or more types, the amount of component A is the total amount thereof.

[acid]
The acid contained in or mixed with the etching solution of the present disclosure is an acid containing an organic acid, nitric acid, and phosphoric acid. In terms of storage stability, the acid contained in or mixed with the etching solution of the present disclosure in one or more embodiments may be an acid consisting of an organic acid, nitric acid, and phosphoric acid (mixed acid).
The amount of acid blended in the etching solution of the present disclosure is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, from the viewpoints of etching inhibition and storage stability.

(organic acid)
From the viewpoint of storage stability, the organic acid may be at least one selected from acetic acid, acetic anhydride, methoxyacetic acid, ethoxyacetic acid, propionic acid, butanoic acid, citric acid, formic acid, gluconic acid, glycolic acid, malonic acid, oxalic acid, lactic acid, and pentanoic acid. Among these, from the same viewpoint, the organic acid is preferably at least one selected from acetic acid, acetic anhydride, methoxyacetic acid, and ethoxyacetic acid, and more preferably acetic acid. The organic acid may be one type or a combination of two or more types. When acetic anhydride is used as the organic acid in preparing the etching solution of the present disclosure, acetic anhydride reacts with the moisture in the etching solution to convert it into acetic acid and water, and the amount of moisture in the etching solution can be reduced.
The amount of organic acid in the etching solution of the present disclosure is 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more or 85% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less, from the viewpoint of improving the quality and storage stability of the etched layer, and from the viewpoint of reducing the viscosity of the etching solution. More specifically, the amount of organic acid in the etching solution of the present disclosure is preferably 50% by mass or more and 95% by mass or less, more preferably 70% by mass or more and 90% by mass or less, or more preferably 80% by mass or more and 90% by mass or less. When two or more organic acids are used in combination, the amount of organic acid is the total amount of the organic acids.
Therefore, in another aspect, the present disclosure relates to an etching solution for etching a layer to be etched that contains at least one metal, the etching solution comprising a component A and an acid containing an organic acid, nitric acid, and phosphoric acid, the amount of the organic acid in the etching solution being 80 mass% or more.

(nitric acid)
The amount of nitric acid in the etching solution of the present disclosure is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more from the viewpoint of improving the quality of the layer to be etched, and is preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 5% by mass or less from the viewpoint of improving the quality of the layer to be etched and storage stability. More specifically, the amount of nitric acid in the etching solution of the present disclosure is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.5% by mass or more and 8% by mass or less, and even more preferably 1% by mass or more and 5% by mass or less.

(phosphoric acid)
The amount of phosphoric acid in the etching solution of the present disclosure is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, from the viewpoint of improving the quality of the layer to be etched and the storage stability, and is preferably 40% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less. More specifically, the amount of phosphoric acid in the etching solution of the present disclosure is preferably 0.1% by mass or more and 40% by mass or less, more preferably 0.5% by mass or more and 20% by mass or less, and even more preferably 1% by mass or more and 10% by mass or less.

The mass ratio of the organic acid to phosphoric acid in the etching solution of the present disclosure (organic acid/phosphoric acid) is preferably 1.2 or more, more preferably 3.5 or more, 5 or more, or 6 or more, from the viewpoint of etching inhibition, and is preferably 950 or less, more preferably 100 or less, 50 or less, or 20 or less, from the viewpoint of etching inhibition as well. More specifically, the mass ratio (organic acid/phosphoric acid) in the etching solution of the present disclosure is preferably 1.2 or more and 950 or less, more preferably 3.5 or more and 100 or less, 5 or more and 50 or less, or 6 or more and 20 or less.

The mass ratio (organic acid/nitrogen-containing compound) of the amount of the organic acid and the nitrogen-containing compound (component A) in the etching solution of the present disclosure is preferably 10 or more, more preferably 20 or more, even more preferably 30 or more, even more preferably 40 or more, even more preferably 50 or more, and from the same viewpoint, it is preferably 10,000 or less, more preferably 5,000 or less, even more preferably 2,500 or less, even more preferably 1,000 or less, even more preferably 500 or less, and even more preferably 100 or less. More specifically, the mass ratio (organic acid/nitrogen-containing compound) in the etching solution of the present disclosure is preferably 10 or more and 10,000 or less, more preferably 20 or more and 5,000 or less, even more preferably 30 or more and 2,500 or less, even more preferably 40 or more and 1,000 or less, even more preferably 50 or more and 500 or less, and even more preferably 50 or more and 100 or less.

(Other acids)
The acid contained or blended in the etching solution of the present disclosure may further contain an acid other than nitric acid, phosphoric acid, and organic acid. The other acid may be an inorganic acid other than nitric acid and phosphoric acid. Examples of the inorganic acid include hydrochloric acid, sulfuric acid, and hydrofluoric acid.

[water]
In one or more embodiments, the etching solution of the present disclosure further contains or is blended with water. Examples of the water contained in or blended with the etching solution of the present disclosure include distilled water, ion-exchanged water, pure water, and ultrapure water.

From the viewpoint of improving the quality of the layer to be etched, the amount of water in the etching solution of the present disclosure is preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 5% by mass or less.

[Other ingredients]
The etching solution of the present disclosure may further contain other components, such as chelating agents, surfactants, solubilizers, preservatives, rust inhibitors, bactericides, antibacterial agents, and antioxidants, as long as the effects of the present disclosure are not impaired.

In one or more embodiments, the etching solution of the present disclosure may be substantially free of polyalkyleneimine and polyalkylenepolyamine. The polyalkyleneimine may be, for example, polyethyleneimine. The polyalkylenepolyamine may be, for example, a polyalkylenepolyamine containing three or more amino groups in one molecule, such as triethylenetetramine.
The content of polyalkyleneimine and polyalkylenepolyamine in the etching solution of the present disclosure is preferably less than 0.01% by mass, more preferably 0.001% by mass or less, and even more preferably 0% by mass (i.e., none).

[Method of manufacturing the etching solution]
In one embodiment, the etching solution of the present disclosure is obtained by blending component A, an organic acid, an acid including nitric acid and phosphoric acid, water, and, if desired, the above-mentioned optional components by a known method. Thus, in one embodiment, the present disclosure relates to a method for producing an etching solution (hereinafter also referred to as the "method for producing an etching solution of the present disclosure") that includes a step of blending at least component A, an organic acid, nitric acid, phosphoric acid, and water.
In the present disclosure, "blending at least component A, an organic acid, nitric acid, phosphoric acid, and water" includes, in one or more embodiments, simultaneously or sequentially mixing component A, an organic acid, nitric acid, phosphoric acid, water, and, if necessary, the optional components described above. The order of mixing is not particularly limited. The blending can be performed using a mixer such as a propeller-type agitator, liquid circulation agitation by a pump, a homomixer, a homogenizer, an ultrasonic disperser, and a wet ball mill.
In the method for producing an etching solution according to the present disclosure, the preferred amount of each component may be the same as the preferred amount of each component in the etching solution according to the present disclosure described above.

In the present disclosure, "the amount of each component in the etching solution" refers, in one or a plurality of embodiments, to the amount of each component of the etching solution used in the etching step, i.e., at the time when the etching solution starts to be used for the etching treatment (at the time of use).
In one or more embodiments, the amount of each component in the etching solution of the present disclosure can be regarded as the content of each component in the etching solution of the present disclosure. However, when the component is affected by neutralization, the amount of each component may differ from the content.

The embodiment of the etching solution of the present disclosure may be a so-called one-liquid type in which all components are supplied to the market in a premixed state, or a so-called two-liquid type in which the components are mixed at the time of use. One embodiment of the two-liquid type etching solution is composed of a solution (first liquid) containing component A and an acid aqueous solution (second liquid) containing an organic acid, nitric acid, and phosphoric acid, and the first liquid and the second liquid are mixed at the time of use. After the first liquid and the second liquid are mixed, they may be diluted with water or an acid aqueous solution as necessary. The first liquid or the second liquid may contain all or a part of the water used to prepare the etching solution. The first liquid and the second liquid may each contain the above-mentioned optional components as necessary.

From the viewpoint of storage stability, the pH of the etching solution of the present disclosure is preferably 2 or less, and more preferably 1 or less. The pH of the etching solution of the present disclosure can be preferably -2.5 or more, and more preferably -2 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.

The viscosity of the etching solution of the present disclosure at 25°C is preferably 1 mPa·s or more, more preferably 2 mPa·s or more, from the viewpoint of improving the quality of the layer to be etched, and is preferably 40 mPa·s or less, more preferably 25 mPa·s or less, and even more preferably 10 mPa·s or less, from the viewpoint of improving the quality of the layer to be etched. More specifically, the viscosity of the etching solution of the present disclosure is preferably 1 mPa·s or more and 25 mPa·s or less, and more preferably 2 mPa·s or more and 10 mPa·s or less. In the present disclosure, the viscosity of the etching solution can be measured using a general-purpose viscometer such as a B-type viscometer or an Ubbelohde viscometer, and specifically, can be measured by the method described in the Examples. The viscosity of the etching solution at 25°C can be adjusted, for example, by water or an organic solvent.

The etching solution of the present disclosure may be stored and supplied in a concentrated state to the extent that its stability is not impaired. This is preferable in that production and transportation costs can be reduced. This concentrated solution can then be appropriately diluted with water or an aqueous acid solution as necessary before use in the etching process. The dilution ratio can be, for example, 5 to 100 times.

[kit]
In another aspect, the present disclosure relates to a kit for producing the etching solution of the present disclosure (hereinafter also referred to as the "kit of the present disclosure").
The kit of the present disclosure includes, for example, a kit (two-liquid etching solution) that contains a solution (first liquid) containing component A and an acid aqueous solution (second liquid) containing an organic acid, nitric acid, and phosphoric acid in a mutually unmixed state, and is mixed at the time of use. After the first liquid and the second liquid are mixed, they may be diluted with water or an acid aqueous solution as necessary. The first liquid or the second liquid may contain all or a part of the water used to prepare the etching solution. The first liquid and the second liquid may each contain the above-mentioned optional components as necessary. According to the kit of the present disclosure, an etching solution with excellent storage stability can be prepared.

[Layer to be etched]
In one or more embodiments, the layer to be etched using the etching solution of the present disclosure is a layer to be etched that contains at least one metal. Here, the metal is not particularly limited as long as the effect of the present disclosure is exhibited, but for example, at least one metal selected from tungsten, tantalum, zirconium, hafnium, molybdenum, niobium, ruthenium, osmium, rhenium, rhodium, copper, nickel, cobalt, titanium, titanium nitride, alumina, aluminum and iridium can be mentioned. Among these, in one or more embodiments, the etching solution of the present disclosure is preferably used for etching a layer to be etched that contains at least one metal selected from tungsten, molybdenum, niobium, tantalum and zirconium, and in one or more embodiments, it is preferably used for etching a molybdenum film. That is, in one or more embodiments, the layer to be etched can be a molybdenum film.
Therefore, in another aspect, the present disclosure relates to an etching solution for etching a layer to be etched that contains molybdenum, the etching solution comprising a component A and an acid that contains an organic acid, nitric acid, and phosphoric acid, the amount of the organic acid in the etching solution being 50 mass% or more.
In one or more embodiments, the layer to be etched is a layer to be etched formed on a substrate, which may be at least one substrate selected from the group consisting of a semiconductor wafer (semiconductor substrate), a substrate for a liquid crystal display device, a substrate for a plasma display, a substrate for a field emission display (FED), a substrate for an optical disk, a substrate for a magnetic disk, a substrate for a magneto-optical disk, a substrate for a photomask, a ceramic substrate, and a substrate for a solar cell.

[Etching method]
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 at least one metal using the etching solution of the present disclosure (hereinafter also referred to as the "etching step of the present disclosure"), and in which the temperature of the etching solution during etching is 20° C. or more and 50° C. or less. According to the etching method of the present disclosure, in one or more embodiments, the productivity of semiconductor substrates can be improved by using an etching solution having excellent storage stability.

In the etching process of the present disclosure, examples of the etching method include immersion etching and single-wafer etching.

The temperature of the etching solution during etching in the etching process of the present disclosure (etching temperature) is preferably 20°C or higher, more preferably 25°C or higher, and even more preferably 30°C or higher, from the viewpoint of improving the quality of the layer to be etched, and is preferably 50°C or lower, more preferably 45°C or lower, and even more preferably 40°C or lower, from the viewpoint of improving the quality of the layer to be etched. More specifically, the etching temperature is preferably 20°C or higher and 50°C or lower, more preferably 25°C or higher and 45°C or lower, and even more preferably 30°C or higher and 40°C or lower.

In the etching process of the present disclosure, the etching time can be set, for example, from 1 minute to 180 minutes. From the viewpoint of improving the quality of the layer to be etched, it is preferably from 15 minutes to 90 minutes, more preferably from 30 minutes to 60 minutes.

In one or more embodiments, the etching solution and the etching method of the present disclosure can be used to etch metals in the manufacturing process of electronic devices, particularly semiconductor wafers (semiconductor substrates). Examples of the metals include those described above.
In one or more embodiments, the etching solution and the etching method of the present disclosure can be suitably used for producing at least one type of substrate selected from a semiconductor wafer (semiconductor substrate), a substrate for a liquid crystal display device, a substrate for a plasma display, a substrate for an FED (Field Emission Display), a substrate for an optical disk, a substrate for a magnetic disk, a substrate for a magneto-optical disk, a substrate for a photomask, a ceramic substrate, and a substrate for a solar cell. This allows uniform etching of the layer to be etched, and improves productivity and yield.
In one or a plurality of embodiments, the etching solution and 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 solution and the etching method of the present disclosure can be suitably used for producing a pattern having a three-dimensional structure, thereby making it possible to obtain an advanced device such as a large-capacity memory.
The etching solution and the etching method of the present disclosure can be used, for example, in an etching method such as that disclosed in JP2020-145412A.

[Electronic component manufacturing method]
In one aspect, the present disclosure relates to a method for producing an electronic component (hereinafter also referred to as the "electronic component production method of the present disclosure"), which includes a step (etching step) of etching an etched layer containing at least one metal using the etching solution of the present disclosure. Examples of electronic components include at least one substrate selected from a semiconductor wafer (semiconductor substrate), a substrate for a liquid crystal display device, a substrate for a plasma display, a substrate for an FED (Field Emission Display), a substrate for an optical disk, a substrate for a magnetic disk, a substrate for a magneto-optical disk, a substrate for a photomask, a ceramic substrate, and a substrate for a solar cell; a semiconductor memory such as a non-volatile memory including a NAND flash memory; and the like. Examples of the etching method and etching conditions in the etching step of the electronic component production method of the present disclosure include the same etching method and etching conditions as those in the etching step of the etching method of the present disclosure described above. Examples of the etched layer include the above-mentioned etched layer.

The present disclosure will be explained in detail below with reference to examples, but the present disclosure is not limited to these examples.

1. Preparation of Etching Solution (Examples 1 to 15, Comparative Examples 1 to 9)
Nitric acid, phosphoric acid, acetic acid, a nitrogen-containing compound, and water shown in Table 1 were mixed to obtain etching solutions (pH: -2.0 to -1.5) of Examples 1 to 15 and Comparative Examples 1 to 9.
The amount of each component (mass %, effective amount) is shown in Table 1. The amount of water is the remainder excluding the acid and the nitrogen-containing compound. The amount of water also includes the amount of water contained in the acid aqueous solution, etc.

The following components were used to prepare the etching solution.
<Acid>
Acetic acid [FUJIFILM Wako Pure Chemical Industries, Ltd., concentration 100%]
Nitric acid [FUJIFILM Wako Pure Chemical Corporation, concentration 70%]
Phosphoric acid [Rinkagaku Kogyo Co., Ltd., concentration 85%]
<Nitrogen-containing compound>
(Aliphatic amines)
Butylamine [Tokyo Chemical Industry Co., Ltd.]
Octylamine [Tokyo Chemical Industry Co., Ltd.]
Dodecylamine [Tokyo Chemical Industry Co., Ltd.]
Octadecylamine [Tokyo Chemical Industry Co., Ltd.]
Methyloctadecylamine [Tokyo Chemical Industry Co., Ltd.]
Dimethyloctadecylamine [Tokyo Chemical Industry Co., Ltd.]
Oleylamine [Tokyo Chemical Industry Co., Ltd.]
2-Ethylhexylamine [Tokyo Chemical Industry Co., Ltd.]
Bis(hexamethylene)triamine [Tokyo Chemical Industry Co., Ltd.]
(Aromatic amines)
Aniline [Tokyo Chemical Industry Co., Ltd.]
2,6-Diisopropylaniline [Tokyo Chemical Industry Co., Ltd.]
5-Methylbenzotriazole [Tokyo Chemical Industry Co., Ltd.]
(Amino alcohol)
2-(2-aminoethoxy)ethanol [Tokyo Chemical Industry Co., Ltd.]
(Phenols)
Catechol [Tokyo Chemical Industry Co., Ltd.]
(Polyalkylenepolyamine)
Triethylenetetramine [molecular weight 146.23, Tosoh Corporation]
(Polyalkyleneimine)
Polyethyleneimine (PEI) [number average molecular weight 1,800, "Epomin SP-018" manufactured by Nippon Shokubai Co., Ltd.]
<Water>
Water [ultrapure water produced using a continuous pure water production system (Pure Conti PC-2000VRL type) and subsystem (Macace KC-05H type) manufactured by Kurita Water Industries Ltd.]

[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.

[Viscosity of Etching Solution]
The viscosity (unit: mPa·s) of the etching solution was measured using the following viscometer under the following conditions.
Device name: TVB-10 viscometer (with thermostatic chamber) manufactured by Toki Sangyo Co., Ltd.
Rotor: Spindle No. M1, Cord No. 20
Rotation speed: 100 rpm, viscosity value measured after 60 seconds Measurement temperature: 25°C
After the temperature in the thermostatic chamber indicated by the device reaches 25°C, 30 minutes later, the viscosity is measured.

2. Evaluation of etching solution [Solubility (storage stability)]
The mixed acid and nitrogen-containing compound shown in Table 1 were mixed in the amounts (mass%) shown in Table 1 to prepare 20 mL of etching solution. After stirring for 10 minutes, the solubility was confirmed by visual observation. The evaluation criteria for solubility are shown in Table 1, with A being the case where there is no residual and the etching solution is colorless and transparent or pale yellow and transparent in the temperature range of 0°C to 40°C, B being the case where there is residual but the etching solution is colorless and transparent or pale yellow and transparent in the temperature range of 0°C to 40°C, and C being the case where the etching solution is cloudy or in other states (for example, changed to black) in the temperature range of 0°C to 40°C. Any points that should be noted separately are also listed in the same column.

[Evaluation of Etching Inhibition Rate]
Taking a specific etching solution as an example, the etching rate of the mixed acid alone constituting the etching solution is α, and the etching rate of the etching solution in which the mixed acid and the nitrogen-containing compound are mixed is β. The etching inhibition rate is calculated by the following formula. The results are shown in Table 1.
Etching inhibition rate (%) = 100 × (α-β)/α

[Substrate surface condition]
A molybdenum plate having a length of 2 cm, a width of 2 cm, and a thickness of 0.1 mm, the weight of which was measured in advance, was immersed in the etching solution (Examples 1 to 15 and Comparative Examples 1 to 5 and 9) prepared to each composition shown in Table 1, and the molybdenum plate was etched at each temperature and each treatment time. However, the etching solution containing a mixed acid alone and a nitrogen-containing compound was tested under the same etching conditions. After washing with water, the surface of the molybdenum plate was observed again using a shape measuring laser microscope VK-9710 (lens magnification 150 times) manufactured by KEYENCE Corporation, and a photograph was analyzed in the surface roughness mode of the same device. Then, the surface accuracy, which is an index of etching unevenness, was calculated by the following formula. The etching unevenness of the molybdenum plate was evaluated based on the following evaluation criteria. The results are shown in Table 1.
Surface precision (%) = surface roughness after etching/surface roughness before etching x 100
<Evaluation criteria>
4: Surface accuracy less than 150% 3: Surface accuracy 150% or more but less than 200% 2: Surface accuracy 200% or more but less than 300% 1: Surface accuracy 300% or more

As shown in Table 1, it was found that all of the etching solutions of Examples 1 to 15, which contained a nitrogen-containing compound having a C/N ratio of 2.2 or more as the nitrogen-containing compound, had better solubility and superior storage stability than the etching solution of Comparative Example 6, which contained catechol (a phenol) instead of the nitrogen-containing compound, and the etching solutions of Comparative Examples 7 and 8, which contained a nitrogen-containing compound having a C/N ratio of less than 2.2 as the nitrogen-containing compound.
Furthermore, the etching solutions of Examples 1 to 15, which contained 50% by mass or more of acetic acid and a nitrogen-containing compound with a C/N ratio of 2.2 or more, had superior etching inhibition and provided better substrate surface conditions than the etching solutions of Comparative Examples 2 to 4, which contained 50% by mass or more of acetic acid and no nitrogen-containing compound, and Comparative Example 5, which contained 30% by mass of acetic acid and no nitrogen-containing compound.
Furthermore, the etching solution of Comparative Example 9, in which the amount of acetic acid was less than 50% by mass, did not provide a good condition of the substrate surface, as compared with Examples 1, 8, and 15, in which the amount of acetic acid was 50% by mass or more.

The etching solution disclosed herein has excellent storage stability, suppresses etching, and improves the quality of the surface of the layer to be etched after etching, making it useful in the manufacturing method of large-capacity semiconductor memories.

Claims (11)

An etching solution for etching a layer to be etched that contains at least one metal,
a nitrogen-containing compound having a ratio C/N of the number of carbon atoms (C) to the number of nitrogen atoms (N) in one molecule of 2.2 or more;
an acid including an organic acid, nitric acid, and phosphoric acid;
It is made by blending
The etching solution has an organic acid content of 80 mass % or more. An etching solution for etching a layer to be etched that contains molybdenum,
at least one nitrogen-containing compound having a ratio C/N of the number of carbon atoms (C) to the number of nitrogen atoms (N) in one molecule of 2.2 or more;
an acid including an organic acid, nitric acid, and phosphoric acid;
It is made by blending
The etching solution has an organic acid content of 50 mass % or more. 3. The etching solution according to claim 1 , wherein the nitrogen-containing compound is at least one selected from the group consisting of an aliphatic amine, an aromatic amine, and an amino alcohol. 4. The etching solution according to claim 3 , wherein the aliphatic amine has a ratio C/N of the number of carbon atoms (C) to the number of nitrogen atoms (N) in one molecule of 4 or more. The etching solution according to claim 1 or 2, wherein the organic acid is at least one selected from acetic acid, acetic anhydride, methoxyacetic acid, ethoxyacetic acid, propionic acid, butanoic acid, citric acid, formic acid, gluconic acid, glycolic acid, malonic acid, oxalic acid, lactic acid, and pentanoic acid. The etching solution according to claim 1 or 2, wherein the amount of the nitrogen-containing compound is 0.01% by mass or more and 5% by mass or less. The etching solution according to claim 1 or 2, wherein the mass ratio of the organic acid to the nitrogen-containing compound (organic acid/nitrogen-containing compound) is 10 or more and 10,000 or less. The etching solution according to claim 1 or 2, further comprising water. The etching solution according to claim 1 or 2, wherein the pH of the etching solution is 2 or less. The method includes a step of etching a layer to be etched, the layer including at least one metal, using the etching solution according to claim 1 or 2,
The etching method, wherein the temperature of the etching solution during etching is 20° C. or higher and 50° C. or lower. A method for manufacturing an electronic component, comprising a step of etching a layer to be etched that contains at least one metal using the etching solution according to claim 1 or 2.