Recess etching solution, recess etching method, and method for manufacturing a surface-treated semiconductor substrate

Abstract

The present invention relates to: a recess etching solution for applying recess etching to metal wiring in a semiconductor substrate manufacturing process; and a recess etching method employing the same. A recess etching solution according to the present invention is for applying recess etching to a surface of a cobalt-containing metal layer embedded in a via or a trench formed in a semiconductor substrate, and contains (A) an organic acid, one of or both of (B) a nitrogen-containing heterocyclic compound and (C) an organic solvent, and (D) water. In addition, a recess etching method according to the present invention includes a recess etching step for applying recess etching to a surface of a cobalt-containing metal layer by bringing the recess etching solution into contact with the surface of the cobalt-containing metal layer embedded in a via or a trench formed in a semiconductor substrate.

Description

Technical Field

[0001] The present invention relates to a recess etching solution, a recess etching method, a method for manufacturing a surface-treated semiconductor substrate, and a method for manufacturing a semiconductor device.

Background Art

[0002] In recent years, with the miniaturization, weight reduction, and high functionality of electronic devices, there has been a strong demand for miniaturization and high density of metal wiring in semiconductor devices. Along with this demand for miniaturization and high density, when connecting upper and lower conductor layers in the manufacture of semiconductor substrates, shorts in metal wiring are likely to occur due to misalignment during the formation of metal wiring patterns. As a result, the problem of a decrease in the yield in the semiconductor device manufacturing line has become apparent, and the margin of allowable misalignment during the formation of metal wiring patterns has become narrower. As a technique for improving this problem, a Fully Self Aligned Via (hereinafter also referred to as "FSAV") process has been proposed. As one approach using the FSAV process, it is conceivable to perform recess etching in advance on the metal embedded in a via or trench, which is a lower conductor layer. In Non-Patent Document 1, as an example of recess etching using a chemical solution, a method of treating a cobalt metal layer in one step using a mixture containing either hydrogen peroxide and hydrofluoric acid or acetic acid, and a method of repeatedly performing an oxidation treatment with hydrogen peroxide and an etching treatment with acetic acid were compared. As a result, it was disclosed that the latter was more suitable in terms of being easier to control the amount of recess etching. Patent Document 1 also describes a method of repeatedly performing an oxidation treatment of a metal layer on the substrate surface with an oxidation fluid and an etching treatment of the oxidized metal layer with an etching solution.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

[0004] [Non-Patent Document 1] Y. Akanishi et al., ECS Transactions, 92 (2) 255-263 (2019) [Overview of the project] [Problems that the invention aims to solve]

[0005] However, the method of repeatedly performing oxidation and etching treatments as proposed in Patent Document 1 and Non-Patent Document 1 has problems such as requiring a long time for recess etching or having a complex process. Furthermore, in order to obtain highly reliable wiring that is less prone to electromigration, the smoothness of the etched surface when recess etching is performed on the metal embedded in the vias or trenches, which are the conductor layers, is crucial. Under these circumstances, it is desirable to provide a recess etching solution and a recess etching method using the same that can perform recess etching on metal wiring in a shorter time and more uniformly. [Means for solving the problem]

[0006] The present invention relates to the recess etching solution, recess etching method, semiconductor substrate manufacturing method, and semiconductor device manufacturing method described below. [1] A recess etching solution for performing recess etching on the surface of a cobalt-containing metal layer embedded in vias or trenches formed in a semiconductor substrate, The recess etching solution comprises (A) an organic acid, (B) a nitrogen-containing heterocyclic compound, and (C) an organic solvent, or both, and (D) water. [2] The recess etching solution according to [1], comprising (A) an organic acid, (B) a nitrogen-containing heterocyclic compound, (C) an organic solvent, and (D) water. [3] The recess etching solution according to [1] or [2], wherein component (A) is one or more selected from the group consisting of aliphatic carboxylic acids having 1 to 12 carbon atoms and aromatic carboxylic acids having 6 to 16 carbon atoms. [4] The recess etching solution according to [3], wherein the aromatic carboxylic acid is one or more selected from the group consisting of benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, 3-hydroxybenzoic acid, and 4-hydroxybenzoic acid. [5] The recess etching solution according to [3] or [4], wherein the aliphatic carboxylic acid is one or more selected from the group consisting of acetic acid and citric acid. [6] The recess etching solution according to any one of the above [1] to [5], wherein component (B) is one or more selected from the group consisting of triazoles, tetrazoles, thiazoles, pyrazoles, imidazoles, and nucleic acid bases. [7] The recess etching solution according to any one of the claims [1] to [6], wherein component (B) is one or more selected from the group consisting of 1,2,3-triazole, 1,2,4-triazole, 3,5-dimethyl-1,2,4-triazole, 3-amino-1,2,4-triazole, 4-amino-1,2,4-triazole, 3-mercapto-4-methyl-4H-1,2,4-triazole, 1H-benzotriazole, 1H-benzotriazole-1-methanol, 4-methyl-1H-benzotriazole, 2-(2-hydroxy-5-methylphenyl)benzotriazole, 5-methyl-1H-benzotriazole, 3-chloro-1H-benzotriazole, 5-chloro-1H-benzotriazole, 1,2,4-triazole-3-carboxylate methyl, 2-(5-chloro-2-benzotriazol)-6-tertbutyl-p-cresol, and 3-amino-1H-triazole. [8] The recess etching solution according to any one of the above [1] to [7], wherein component (C) is one or more selected from the group consisting of organic solvents having an HLB (Hydrophile-Lipophile Balance) value of 3 to 15. [9] The recess etching solution according to any one of the above [1] to [8], wherein component (C) is one or more selected from the group consisting of 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, cyclohexanol, ethylene glycol, propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,2-pentanediol, 1,5-pentanediol, 2,4-pentanediol, diethylene glycol, dipropylene glycol, dibutylene glycol, triethylene glycol, tripropylene glycol, 1,2-hexanediol, 1,6-hexanediol, neopentyl glycol, glycerin, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, acetone, and methyl ethyl ketone.

[10] A recess etching solution according to any one of the above [1] to [9], comprising (A) 0.001 to 10% by mass of an organic acid, (B) 0.001 to 5% by mass of a nitrogen-containing heterocyclic compound, and (C) 1 to 99% by mass of an organic solvent.

[11] A recess etching solution according to any one of the above [1] to

[10] , wherein the pH value is in the range of 1.0 to 6.0.

[12] A recess etching method comprising a recess etching step of bringing a recess etching solution according to any one of [1] to

[11] into contact with the surface of a cobalt-containing metal layer embedded in a via or trench formed on a semiconductor substrate to perform recess etching on the surface of the cobalt-containing metal layer.

[13] A method for manufacturing a surface-treated semiconductor substrate, comprising a recess etching step of bringing a recess etching solution described in any one of [1] to

[11] into contact with the surface of a cobalt-containing metal layer embedded in vias or trenches formed on the semiconductor substrate to perform recess etching on the surface of the cobalt-containing metal layer.

[14] A recess etching step in which a recess etching solution described in any one of [1] to

[11] is brought into contact with the surface of a cobalt-containing metal layer embedded in a via or trench formed on a semiconductor substrate, and recess etching is performed on the surface of the cobalt-containing metal layer. A step to obtain a semiconductor substrate in which a wiring circuit is constructed by stacking metal wiring layers on the surface of a cobalt-containing metal layer on a surface-treated semiconductor substrate obtained in the above step, A method for manufacturing a semiconductor element, comprising the step of obtaining a semiconductor element by cutting a semiconductor substrate on which a wiring circuit obtained in the above step is constructed into a predetermined shape. [Effects of the Invention]

[0007] According to the present invention, recess etching can be performed on metal wiring containing a cobalt-containing metal layer more efficiently and in a shorter time by processing in a single step. In a preferred embodiment of the present invention, the amount of recess etching can be controlled, and a more uniform and smooth recess etching surface can be formed. [Brief explanation of the drawing]

[0008] [Figure 1] This is a diagram illustrating the process of the recess etching method according to the present invention. [Figure 2] This is a cross-sectional SEM image of the evaluation sample obtained in Example 11 after etching. [Modes for carrying out the invention]

[0009] 1. Recess etching solution The recess etching solution according to the present invention is a recess etching solution for performing recess etching on the surface of a cobalt-containing metal layer embedded in vias or trenches formed in a semiconductor substrate, The present invention is characterized by comprising (A) an organic acid, (B) a nitrogen-containing heterocyclic compound and (C) an organic solvent, or both, and (D) water. The recess etching solution according to the present invention enables recess etching to be performed efficiently in a shorter time because it can perform recess etching on the surface of a cobalt-containing metal layer embedded in a via or trench formed in a semiconductor substrate in one step without performing an oxidation treatment and an etching treatment in separate steps. Hereinafter, in this specification, (A) an organic acid may be referred to as "component (A)", (B) a nitrogen-containing heterocyclic compound may be referred to as "component (B)", (C) an organic solvent may be referred to as "component (C)", and (D) water may be referred to as "component (D)".

[0010] The recess etching solution according to the present invention is used to perform recess etching on the surface of a cobalt-containing metal layer embedded in a via or trench formed in a semiconductor substrate. In the present invention, the cobalt-containing metal layer to be subjected to recess etching is a metal layer containing cobalt. In the cobalt-containing metal layer, the content of cobalt is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more, even more preferably 95% by mass or more, and may be 99% by mass or more. The cobalt-containing metal layer may contain components other than cobalt. For example, if it is in the range of less than 50% by mass, it may contain other metal components.

[0011] Generally, it is known that cobalt has crystal regions having various crystal orientations and grain sizes, and amorphous regions and gaps exist at the grain boundaries thereof. Due to this, in the cobalt-containing metal layer embedded in a via or trench formed in a semiconductor substrate, there are two types of partial corrosion: corrosion caused by the oxidation (aging) of cobalt over time and galvanic corrosion (Co → Co 2+ + 2e - ) caused by the corrosion potential difference between crystal orientations. Cobalt in the amorphous region or near the gap is easily oxidized by aging, and the oxidized cobalt is quickly etched by an acid-based chemical solution. Also, when there is a corrosion potential difference between crystal orientations, galvanic corrosion is likely to occur in a specific crystal orientation, and it is considered that corrosion by the chemical solution progresses locally easily. In particular, in the case of a particularly fine wiring pattern, the grain size tends to be small and the proportion occupied by grain boundaries increases, making it difficult to obtain a smooth etching surface. From these facts, in order to form a smooth etching surface on a cobalt-containing metal layer embedded in a via or trench formed in a semiconductor substrate, it is necessary to suppress the partial corrosion of cobalt in the cobalt-containing metal layer.

[0012] As a result of studying components that can exhibit the effect of suppressing these partial corrosions, the inventors of the present invention have found that, in addition to the component (A) having an etching action, by using either one or both of the component (B) and the component (C), in a single liquid, while suppressing the partial corrosion of cobalt, it is possible to perform recess etching in one step on the surface of a cobalt-containing metal layer embedded in a via or trench formed in a semiconductor substrate. According to a preferred embodiment of the present invention, by suppressing the partial corrosion of cobalt in this way, an etching surface excellent in smoothness can be obtained.

[0013] The component (B) has a corrosion preventive action on cobalt. By the component (B) adsorbing on the surface of the cobalt-containing metal layer, it is presumed that the corrosion potential of all crystal orientations shifts nobly, and due to this effect, the corrosion potential difference between crystal orientations becomes small, thereby suppressing galvanic corrosion. The component (C) has an action of destabilizing cobalt ions (Co 2+ ) generated by galvanic corrosion compared to water. Therefore, it is presumed that the component (C) has an action of reducing the galvanic corrosion of cobalt. Further, the etching of cobalt occurs by oxidation and dissolution as represented by the following formula, but the component (C) causes cobalt ions (Co 2+Because component (C) destabilizes the material, the dissolution of cobalt oxide slows down. This allows for a gradual etching of cobalt oxide produced during aging, thereby suppressing partial corrosion of cobalt. Furthermore, organic solvents are generally more hydrophobic than water, and therefore have a higher dissolved oxygen concentration. Consequently, the oxidation rate of cobalt increases due to the effect of component (C). In other words, although the oxidation rate increases due to component (C), the dissolution rate decreases, so the etching rate of cobalt is thought to be balanced, and it is presumed that the etching rate of cobalt is not significantly impaired by component (C). [ka]

[0014] Based on the above theory, it is possible to derive recess etching solutions suitable not only for cobalt-containing metal layers but also for other metal layers. However, the above theory is based on speculation about the mechanism by which recess etching is controlled, and the present invention is not bound in any way by the above theory.

[0015] As described above, component (B) and component (C) are thought to have the effect of suppressing the partial corrosion of cobalt. In the present invention, only one of component (B) and component (C) may be used, or both component (B) and component (C) may be used. According to one embodiment of the present invention, it is preferable to use both component (B) and component (C). By using both component (B) and component (C), the partial corrosion of cobalt can be suppressed more effectively, and a smoother etched surface may be obtained.

[0016] The following explains each component.

[0017] (A) Organic acid (component (A)) As described above, in the recess etching solution according to the present invention, component (A) has an etching effect on the cobalt-containing metal layer. The organic acid of component (A) is not particularly limited as long as it is an organic compound having a carboxyl group. Examples of component (A) include aliphatic carboxylic acids, aromatic carboxylic acids, and amino acids. Among these, aliphatic carboxylic acids and aromatic carboxylic acids are preferred, and it is more preferable that one or more are selected from the group consisting of aliphatic carboxylic acids having 1 to 12 carbon atoms and aromatic carboxylic acids having 6 to 16 carbon atoms.

[0018] Examples of aliphatic carboxylic acids include formic acid, acetic acid, propionic acid, lactic acid, glycolic acid, diglycolic acid, pyruvic acid, oxaloacetate, oxalic acid, malonic acid, butyric acid, hydroxybutyric acid, tartaric acid, succinic acid, malic acid, maleic acid, fumaric acid, valeric acid, glutaric acid, itaconic acid, adipic acid, caproic acid, citric acid, propanetricarboxylic acid, trans-aconitic acid, enanthic acid, caprylic acid, nonanoic acid, capric acid, lauric acid, myristic acid, palmitic acid, sorbic acid, iminodiacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraaminehexaacetic acid, and diaminocyclohexanetetraacetic acid. These can be used individually or in combination of two or more types. Among these, acetic acid, citric acid, and combinations thereof are preferred as aliphatic carboxylic acids.

[0019] Examples of aromatic carboxylic acids include benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, mandelic acid, 2-methylbenzoic acid, 3-methylbenzoic acid, 4-methylbenzoic acid, 2-ethylbenzoic acid, 3-ethylbenzoic acid, 4-ethylbenzoic acid, salicylic acid, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, 2-chlorobenzoic acid, 3-chlorobenzoic acid, 4-chlorobenzoic acid, 2-fluorobenzoic acid, 3-fluorobenzoic acid, 4-fluorobenzoic acid, 2-cyanobenzoic acid, 3-cyanobenzoic acid, and 4-cyanobenzoic acid. 2-nitrobenzoic acid, 2-nitrobenzoic acid, 3-nitrobenzoic acid, 4-nitrobenzoic acid, 2,3-dimethylbenzoic acid, 3,4-dimethylbenzoic acid, 3,5-dimethylbenzoic acid, 2,5-dimethylbenzoic acid, 2,6-dimethylbenzoic acid, 2-hydroxy-3-methylbenzoic acid, 2-hydroxy-4-methylbenzoic acid, 2-hydroxy-5-methylbenzoic acid, 2-hydroxy-6-methylbenzoic acid, 3-hydroxy-2-methylbenzoic acid, 3-hydroxy-4-methylbenzoic acid, 3-hydroxy-5-methylbenzoic acid Acids, 3-hydroxy-6-methylbenzoic acid, 4-hydroxy-2-methylbenzoic acid, 4-hydroxy-3-methylbenzoic acid, 2-methoxybenzoic acid, 3-methoxybenzoic acid, 4-methoxybenzoic acid, 2,3-dihydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid, 3,4-dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid, 3,6-dihydroxybenzoic acid, 2,4,5-trimethylbenzoic acid, 2,4,6-trimethylbenzoic acid Examples include acids, 1-naphthalenecarboxylic acid, 2-naphthalenecarboxylic acid, 1-hydroxy-2-naphthalenecarboxylic acid, 6-hydroxy-1-naphthalenecarboxylic acid, 6-hydroxy-2-naphthalenecarboxylic acid, 2-hydroxy-1-naphthalenecarboxylic acid, 3-hydroxy-2-naphthalenecarboxylic acid, 1,4-dihydroxy-2-naphthalenecarboxylic acid, 1-anthracenecarboxylic acid, 2-anthracenecarboxylic acid, 9-anthracenecarboxylic acid, gallic acid, mellitic acid, and cinnamic acid. These can be used individually or in combination of two or more types. Among these, benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, and combinations thereof are preferred as the aromatic carboxylic acid.

[0020] The aforementioned component (A) may consist of either an aliphatic carboxylic acid or an aromatic carboxylic acid, or both an aliphatic carboxylic acid and an aromatic carboxylic acid.

[0021] The content of component (A) is preferably 0.001 to 10% by mass, more preferably 0.01 to 3% by mass, even more preferably 0.03 to 1% by mass, and particularly preferably 0.06 to 0.5% by mass, based on the mass of the recess etching solution. In this specification, when a numerical range is indicated, the upper and lower limits may be combined as appropriate, and the resulting numerical range is also disclosed.

[0022] (B) Nitrogen-containing heterocyclic compound (component (B)) In the recess etching solution according to the present invention, component (B) has the effect of suppressing the partial corrosion of cobalt contained in the cobalt-containing metal layer. The nitrogen-containing heterocyclic compound of component (B) is not particularly limited as long as it is a compound that contains a nitrogen atom as a heteroatom constituting the ring. Examples include triazoles, tetrazoles, thiazoles, pyrazoles, imidazoles, and nucleic acid bases.

[0023] Examples of triazoles include 1,2,3-triazole, 1,2,4-triazole, 3,5-dimethyl-1,2,4-triazole, 3-amino-1,2,4-triazole, 4-amino-1,2,4-triazole, 3-mercapto-4-methyl-4H-1,2,4-triazole, 1H-benzotriazole, 1H-benzotriazole-1-methanol, 4-methyl-1H-benzotriazole, 2-(2-hydroxy-5-methylphenyl)benzotriazole, 5-methyl-1H-benzotriazole, 3-chloro-1H-benzotriazole, 5-chloro-1H-benzotriazole, 1,2,4-triazole-3-carboxylate methyl, 2-(5-chloro-2-benzotriazol)-6-tert-butyl-p-cresol, and 3-amino-1H-triazole. Examples of tetrazoles include 1H-tetrazole, 5-methyl-1H-tetrazole, 5-phenyl-1H-tetrazole, 5-mercapto-1-methyl-1H-tetrazole, 5-mercapto-1-phenyl-1H-tetrazole, 5-benzyl-1H-tetrazole, and 5-amino-1H-tetrazole. Examples of thiazoles include 1,3-thiazole and 4-methylthiazole. Examples of pyrazoles include pyrazole and 3,5-dimethylpyrazole. Examples of imidazoles include imidazole, 2-methylimidazole, 1-propylimidazole, 1-isopropylimidazole, 2-undecylimidazole, 2-phenylimidazole, benzimidazole, 2-methylbenzimidazole, and 2-hydroxybenzimidazole. Examples of nucleic acid bases include purines, adenine, guanine, pyrimidines, uracil, thymine, and cytosine. These can be used individually or in combination of two or more. Among these, triazoles are preferred, and among them, 1,2,4-triazole, 1H-benzotriazole, and 5-methyl-1H-benzotriazole are preferred.

[0024] The content of component (B) is preferably 0.001 to 5% by mass, more preferably 0.01 to 1% by mass, even more preferably 0.025 to 0.4% by mass, and particularly preferably 0.025 to 0.1% by mass, based on the mass of the recess etching solution.

[0025] (C) Organic solvent (component (C)) In the recess etching solution according to the present invention, component (C) has the effect of suppressing the partial corrosion of cobalt contained in the cobalt-containing metal layer. As for the aforementioned component (C), an organic solvent having an HLB (Hydrophile-Lipophile Balance) value of 3 to 15 is preferred. The HLB value is more preferably 3 to 13, even more preferably 3 to 11, and especially preferably 3 to 9. The smaller the HLB value and the higher the hydrophobicity, the more cobalt ions (Co 2+ It has a high effect in destabilizing the process and a high effect in controlling etching.

[0026] Component (C) specifically includes methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol), 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, cyclohexanol, ethylene glycol, propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,2-pentanediol, 1,5-pentanediol, 2,4-pentanediol, diethylene glycol, dipropylene glycol, dibutyric acid Ethylene glycol, triethylene glycol, tripropylene glycol, 1,2-hexanediol, 1,6-hexanediol, neopentyl glycol, glycerin, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, acetone, methyl ethyl ketone, N-methylpyrrolidone, methyl formate, ethyl formate, 1-propyl formate, 2-propyl formate, methyl acetate, ethyl acetate, 1-propyl acetate, 2-propyl acetate, methyl propionate, ethyl propionate, 1-propyl propionate, 2-propyl propionate, dimethyl ethyl Methyl ethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-1-propyl ether, ethylene glycol mono-2-propyl ether, ethylene glycol monophenyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-1-propyl ether, propylene glycol mono-2-propyl ether, propylene glycol monophenyl ether, butylene glycol monomethyl ether, butylene glycol monoethyl ether, butylene glycol mono-1-propyl ether, butylene glycol mono-2-propyl ether, butylene glycol monophenyl ether, ethylene glycol dimethyl ether, ethylene glycol ethyl methyl ether, ethylene glycol diethyl ether, propylene glycol dimethyl ether, propylene glycol ethyl methyl ether, propylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether,Examples include diethylene glycol mono-1-propyl ether, diethylene glycol mono-2-propyl ether, diethylene glycol monophenyl ether, dipropylene glycol dimethyl ether, dipropylene glycol ethyl methyl ether, dipropylene glycol diethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol mono-1-propyl ether, triethylene glycol mono-2-propyl ether, triethylene glycol monophenyl ether, tripropylene glycol dimethyl ether, tripropylene glycol ethyl methyl ether, and tripropylene glycol diethyl ether. These can be used individually or in combination of two or more.

[0027] Among these, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, cyclohexanol, ethylene glycol, propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,2-pentanediol, 1,5-pentanediol, 2,4-pentanediol, diethylene glycol, dipropylene glycol, dibutylene glycol, triethylene glycol, tripropylene glycol, 1,2-hexanediol, 1,6-hexanediol, neopentyl glycol, glycerin, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, acetone, methyl ethyl ketone, and combinations thereof are preferred.

[0028] The content of component (C) is preferably 1 to 99% by mass, more preferably 5 to 80% by mass, even more preferably 10 to 60% by mass, and particularly preferably 30 to 50% by mass, based on the mass of the recess etching solution.

[0029] (D) Water (ingredient (D)) The recess etching solution according to the present invention contains water as a diluent. The water is preferably water from which metal ions, organic impurities, and particle particles have been removed by distillation, ion exchange treatment, filtration treatment, or various adsorption treatments, and pure water or ultrapure water is particularly preferred. The content of component (D) is the remainder of the recess etching solution, and is preferably 1% by mass or more, more preferably in the range of 5 to 99.9% by mass, even more preferably 20 to 99% by mass, even more preferably 30 to 95% by mass, and particularly preferably 35 to 90% by mass, based on the mass of the recess etching solution.

[0030] (E) Other ingredients In addition to components (A), (B), (C), and (D) mentioned above, the recess etching solution according to the present invention may also contain additives such as oxidizing agents, reducing agents, surfactants, chelating agents, inorganic acids, and alkalis that are commonly used for etching cobalt-containing metal layers, to the extent that they do not impede the effects of the present invention. However, the presence of an oxidizing agent can significantly increase the etching rate of cobalt, making it difficult to control the amount of recess etching. Therefore, it is preferable that the recess etching solution according to the present invention does not contain an oxidizing agent. Furthermore, since sulfonium compounds may adsorb onto the cobalt surface and affect the electrical properties of semiconductor devices, it is preferable that the recess etching solution according to the present invention does not contain sulfonium compounds. Furthermore, if inorganic acids (such as sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, sulfamic acid, etc.) are included, the surface after etching may become rough, making it difficult to obtain a smooth surface. Therefore, it is preferable that the inorganic acid content be less than 0.1% by mass of the recess etching solution, or substantially absent. More preferably, the inorganic acid content is less than 0.1% by mass, even more preferably less than 0.01% by mass, and particularly preferably less than 0.001% by mass, based on the mass of the etching solution.

[0031] According to a preferred embodiment of the present invention, the total content of component (A), component (B), component (C), and component (D) is preferably 95% by mass or more, more preferably in the range of 96 to 100% by mass, even more preferably 97 to 100% by mass, even more preferably 98 to 100% by mass, and particularly preferably 99 to 100% by mass, based on the mass of the recess etching solution.

[0032] In the present invention, either or both of component (B) and component (C) are used. When both component (B) and component (C) are used, the recess etching solution according to the present invention preferably contains 0.001 to 10% by mass of component (A), 0.001 to 5% by mass of component (B), 1 to 99% by mass of component (C), and the remainder of component (D). A recess etching solution combining the above-mentioned preferred ranges of content of component (A), component (B), and component (C) is even more preferable.

[0033] Even when only component (B) is contained among the aforementioned components (B) and (C), the preferred content of component (B) remains as described above and does not change significantly. In this case, the recess etching solution according to the present invention preferably contains 0.001 to 10% by mass of component (A), 0.01 to 1% by mass of component (B), and 89 to 99.989% by mass of component (D), more preferably 0.001 to 10% by mass of component (A), 0.025 to 0.4% by mass of component (B), and 89.6 to 99.974% by mass of component (D), and even more preferably 0.001 to 10% by mass of component (A), 0.025 to 0.1% by mass of component (B), and 89.9 to 99.974% by mass of component (D).

[0034] Furthermore, even when only component (C) is contained among the components (B) and (C), the preferred content of component (C) remains as described above and does not change significantly. In this case, the recess etching solution according to the present invention preferably contains 0.001 to 10% by mass of component (A), 5 to 80% by mass of component (C), and 10 to 94.999% by mass of component (D), more preferably 0.001 to 10% by mass of component (A), 10 to 60% by mass of component (C), and 30 to 89.999% by mass of component (D), and even more preferably 0.001 to 10% by mass of component (A), 30 to 50% by mass of component (C), and 40 to 69.999% by mass of component (D).

[0035] In the present invention, the pH value of the recess etching solution is not particularly limited, but is preferably in the range of 1.0 to 6.0, more preferably 1.5 to 4.5, even more preferably 2.3 to 3.8, and most preferably 2.3 to 3.6. In the recess etching solution according to the present invention, a pH adjusting agent may be added as needed to adjust the pH range. Examples of pH adjusting agents include potassium hydroxide, lithium hydroxide, cesium hydroxide, triethylamine, ammonia, tetramethylammonium hydroxide, ethanolamine, and 1-amino-2-propanol. One or more pH adjusting agents may be used.

[0036] The recess etching solution according to the present invention can be prepared by uniformly stirring components (A) to (D), and any other components (E) as needed. Note that some or all of the water in component (D) may be added later. Alternatively, a solution containing components (A) to (C), some of component (D), and any other components (E) may be prepared in advance and stored, and then diluted with the remainder of component (D) before use.

[0037] 2. Recess Etching Method The recess etching method according to the present invention is characterized by including a recess etching step of bringing the above-mentioned recess etching solution into contact with the surface of a cobalt-containing metal layer embedded in a via or trench formed in a semiconductor substrate, thereby performing recess etching on the surface of the cobalt-containing metal layer. Figure 1 is a diagram illustrating the process of the recess etching method according to the present invention. Note that Figure 1 schematically shows only the structures necessary to explain the process of the recess etching method.

[0038] First, as shown in Figure 1(a), a semiconductor substrate 100 is prepared having a wiring structure in which vias or trenches are formed in an interlayer insulating film 20 provided on a substrate 10, and a cobalt-containing metal layer 30 is embedded within these vias or trenches. A barrier metal layer 40, such as a titanium layer or a titanium nitride layer, may be formed on the inner wall of the via or trench. The semiconductor substrate 100 can be manufactured using methods commonly used in this industry. For example, it can be manufactured as follows: First, an interlayer insulating film 20 is formed on the substrate 10. Next, vias or trenches are formed in the interlayer insulating film 20 by dry etching or the like. Furthermore, a barrier metal layer 40 is formed on the inner wall of the vias or trenches as needed. Next, a cobalt-containing metal layer 30 is formed to fill the vias or trenches formed in the interlayer insulating film 20. Finally, by performing CMP (chemical mechanical polishing) as needed, a semiconductor substrate 100 with a smooth top surface can be obtained.

[0039] Next, as shown in Figure 1(b), the recess etching solution 50 is brought into contact with the surface of the cobalt-containing metal layer 30 exposed on the upper part of the semiconductor substrate 100.

[0040] In the present invention, the method for bringing the recess etching solution 50 into contact with the surface of the cobalt-containing metal layer 30 is not particularly limited. For example, methods such as dropping (single-wafer spin treatment) or spraying the recess etching solution into contact with the surface of the cobalt-containing metal layer, or immersing the surface of the cobalt-containing metal layer in the recess etching solution can be employed.

[0041] The temperature of the recess etching solution 50 when it is brought into contact with the cobalt-containing metal layer 30 is not particularly limited, but for example, it is 0 to 70°C, preferably 25 to 65°C, more preferably 25 to 60°C, and even more preferably 30 to 60°C. If the temperature of the recess etching solution is 25°C or higher, recess etching can be performed in a shorter time. On the other hand, if it is 60°C or lower, changes in the solution composition can be suppressed and the processing conditions can be kept constant.

[0042] The time (processing time) for contacting the cobalt-containing metal layer 30 with the recess etching solution 50 is not particularly limited, but is usually preferably 15 seconds or more and 10 minutes or less, more preferably 30 seconds or more and 7.5 minutes or less, and even more preferably 30 seconds or more and 5 minutes or less. The optimal processing time can be appropriately selected depending on the method of contact between the cobalt-containing metal layer and the recess etching solution, the temperature of the recess etching solution, etc.

[0043] In the recess etching method according to the present invention, the etching rate of the cobalt-containing metal layer is preferably 0.5 to 20 nm / min, more preferably 0.9 to 15 nm / min, even more preferably 0.9 to 10 nm / min, and particularly preferably 0.9 to 7.5 nm / min.

[0044] As described above, by bringing the recess etching solution 50 into contact with the surface of the cobalt-containing metal layer 30, recess etching can be performed on the surface of the cobalt-containing metal layer 30, as shown in Figure 1(c). The barrier metal layer 40 in the recess-etched portion may be removed by etching separately in a subsequent process, or it may be left as is without going through the etching process and the process may proceed to the next step.

[0045] The preferred amount of recess etching applied to the cobalt-containing metal layer by the recess etching method according to the present invention, and the surface roughness of the recess etching surface, are described in "3. Method for manufacturing a surface-treated semiconductor substrate."

[0046] After recess etching is performed by contacting the cobalt-containing metal layer with the recess etching solution described above, the surface may be washed as needed using water, isopropyl alcohol, aqueous ammonia solution, aqueous tetramethylammonium hydroxide solution, etc. Alternatively, rust prevention treatment may be performed using an aqueous solution containing a rust inhibitor.

[0047] 3. Method for manufacturing a surface-treated semiconductor substrate The present invention relates to a method for manufacturing a surface-treated semiconductor substrate, characterized by including a recess etching step in which the surface of a cobalt-containing metal layer embedded in vias or trenches formed in a semiconductor substrate is brought into contact with the above-mentioned recess etching solution to perform recess etching on the surface of the cobalt-containing metal layer. Here, "surface-treated semiconductor substrate" refers to a semiconductor substrate in which recess etching is performed on the surface of a cobalt-containing metal layer embedded in vias or trenches formed in a semiconductor substrate by bringing the surface of the cobalt-containing metal layer into contact with the recess etching solution.

[0048] The method for contacting the recess etching solution with the surface of the cobalt-containing metal layer, the temperature of the recess etching solution during contact, and the contact time are as described in "2. Recess Etching Method" above. Furthermore, as described in "2. Recess Etching Method" above, cleaning may be performed as appropriate after the recess etching process.

[0049] According to the present invention, a surface-treated semiconductor substrate can be manufactured by performing recess etching on the surface of a cobalt-containing metal layer embedded in vias or trenches formed on a semiconductor substrate. In a semiconductor substrate having a wiring structure including a cobalt-containing metal layer manufactured according to the present invention, a wiring circuit can be constructed by further stacking metal wiring layers containing cobalt and copper in the process after recess etching described above.

[0050] The amount of recess etching applied to the cobalt-containing metal layer by recess etching according to the present invention (i.e., the depth of the recess formed by recess etching applied to the cobalt-containing metal layer) is not particularly limited, but from the viewpoint of preventing short circuits of metal wiring due to misalignment during metal wiring pattern formation, it is preferably 2.5 to 20 nm, more preferably 5 to 15 nm, and even more preferably 7.5 to 12.5 nm.

[0051] Furthermore, the surface roughness (Ra) of the recess etching surface applied to the cobalt-containing metal layer by recess etching according to the present invention is preferably 8.5 nm or less, more preferably 5 nm or less, even more preferably 3 nm or less, even more preferably 2.5 nm or less, and particularly preferably 1 nm or less. In the present invention, the surface roughness (Ra) of the recess etching surface refers to the roughness correction value of the cobalt-containing metal layer. The roughness correction value can be measured by the method described in the examples below.

[0052] 4. Method for manufacturing semiconductor devices The method for manufacturing a semiconductor device according to the present invention is: A recess etching step is performed by contacting the surface of a cobalt-containing metal layer embedded in a via or trench formed on a semiconductor substrate with the recess etching solution described above, thereby performing recess etching on the surface of the cobalt-containing metal layer. A step to obtain a semiconductor substrate in which a wiring circuit is constructed by stacking metal wiring layers on the surface of a cobalt-containing metal layer on a surface-treated semiconductor substrate obtained in the above step, The process is characterized by including a step of obtaining a semiconductor element by cutting the semiconductor substrate on which the wiring circuit obtained in the above step is constructed into a predetermined shape. According to the present invention, recess etching can be uniformly applied to the metal wiring during the recess etching process, making it less likely for short circuits to occur in the metal wiring, and thus a semiconductor device with excellent electrical characteristics can be obtained. The metal wiring layers that can be stacked on the surface of the cobalt-containing metal layer are not particularly limited as long as they can be electrically connected to the cobalt-containing metal layer, such as those containing cobalt or copper. The metal wiring layers that can be stacked on the surface of the cobalt-containing metal layer may be one layer or two or more layers. [Examples]

[0053] Next, the present invention will be described in more detail using examples and comparative examples, but the present invention is not limited in any way by these examples.

[0054] Examples 1-18 (1) Preparation of recess etching solution The recess etching solution was prepared by mixing each component in the composition ratios listed in Table 1 and stirring to achieve a homogeneous state.

[0055] (2) Recess etching of the cobalt-containing metal layer For evaluating the recess etching solution, we used a "CVD cobalt film-coated wafer" manufactured by Philtech Co., Ltd., which has a cobalt metal layer (thickness: 90 nm) on the substrate surface. As a pretreatment, an aqueous acetic acid solution (0.01% by mass) was brought into contact with the surface of the evaluation sample at 30°C for 5 minutes to remove oxides present on the surface of the cobalt metal layer. Next, the pre-treated surface of the evaluation sample was immersed in the recess etching solution prepared in (1) at 50°C or 20°C (the processing temperature for each example is shown in Table 1) for the time indicated in Table 1 (the time required to etch a cobalt metal layer thickness of 50 nm, calculated from the etching rate of the cobalt-containing metal layer described later) to perform an etching treatment.

[0056] (3) Calculation of roughness value After etching, evaluation samples were subjected to FIB processing (using Thermo Scientific Helios G4 UX equipment) to obtain smooth cross-sections of the etched evaluation samples. Next, cross-sections of the obtained evaluation samples were observed using a SEM (Scanning Emissory Note: Thermo Scientific Helios G4 UX), and the XY coordinates of roughness were converted from the SEM images into Excel data using ImageJ (developed by Wayne Rasband, National Institutes of Health). The roughness value of the cobalt-containing metal layer was obtained by calculating the standard deviation of the Y coordinate using Excel data. As an example of a cross-section of an evaluation sample after etching, Figure 2 shows a cross-sectional SEM image of the evaluation sample from Example 11 after etching (magnification 100,000x, observation of a range of 2070 nm in the lateral direction).

[0057] <Etching rate of cobalt-containing metal layer (Co.ER)> The etching rate of the cobalt-containing metal layer was calculated by dividing the difference in cobalt metal layer thickness before and after etching by the processing time (5 minutes). An etching rate of 0.5 nm / min or higher was considered acceptable.

[0058] <Roughness correction value for cobalt-containing metal layer (Co roughness correction value)> The roughness value of the cobalt-containing metal layer after etching was obtained using the method described in "(3) Calculation of Roughness Value" above. SEM images were acquired at four different locations in one cross-section obtained by FIB processing, and the average of the four roughness values ​​obtained from each SEM image was defined as "Roughness Value A". Furthermore, using the same method, the roughness value (roughness value B; 6.7 nm) of the cobalt-containing metal layer was calculated after contact with an aqueous acetic acid solution (0.01% by mass) at 30°C for 5 minutes, without immersion in the recess etching solution. The value obtained by subtracting roughness value B from roughness value A was defined as the "roughness correction value," and a roughness correction value of 8.5 nm or less was considered acceptable.

[0059] Comparative Examples 1-9 Recess etching solutions were prepared in the same manner as in the examples, except for the composition ratio and processing time listed in Table 2. The cobalt-containing metal layer was then etched using the evaluation sample. The etching rate and roughness correction value of the cobalt-containing metal layer were calculated in the same manner as in the examples.

[0060] The results are shown in Tables 1 and 2.

[0061] [Table 1]

[0062] [Table 2]

[0063] In the table, the value of hydrofluoric acid is shown as a mass percentage in terms of hydrogen fluoride equivalent.

[0064] As shown in Table 1, by treating a cobalt-containing metal layer with the recess etching solution according to the present invention, the roughness correction value of the cobalt-containing metal layer can be kept low, and a smooth etched surface can be obtained in a single step (Examples 1 to 18). On the other hand, as shown in Table 2, when only organic acids were used and nitrogen-containing heterocyclic compounds and organic solvents were not used (Comparative Examples 1-3), or when only inorganic acids were used (Comparative Examples 4 and 5), or when inorganic acids were combined with either or both nitrogen-containing heterocyclic compounds and organic solvents (Comparative Examples 6-9), the roughness correction value of the cobalt-containing metal layer also increased significantly. As shown in the results above, by processing in a single step using the recess etching solution according to the present invention, a smooth etched surface of the cobalt-containing metal layer can be obtained more efficiently and in a shorter time. Since the recess etching solution according to the present invention is excellent at obtaining a smooth etched surface in the processing of cobalt-containing metal layers, it can be suitably used as a recess etching solution where the smoothness of the etched surface is important. [Explanation of symbols]

[0065] 10 circuit boards 20 Interlayer insulating film 30 Cobalt-containing metal layer 40 Barrier metal layer 50 Recess Etching Solution 60 Recess etching amount 100 semiconductor substrates

Claims

1. A recess etching solution for performing recess etching on the surface of a cobalt-containing metal layer embedded in vias or trenches formed on a semiconductor substrate, (A) an organic acid, (B) a nitrogen-containing heterocyclic compound, and (C) an organic solvent, or both, and (D) water. The organic acid is one or more aromatic carboxylic acids selected from the group consisting of benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, 3-hydroxybenzoic acid, and 4-hydroxybenzoic acid. The pH value is in the range of 1.5 to 4.

5. The recess etching solution having an inorganic acid content of less than 0.01% by mass.

2. The recess etching solution according to claim 1, comprising (A) an organic acid, (B) a nitrogen-containing heterocyclic compound, (C) an organic solvent, and (D) water.

3. The recess etching solution comprises (B) a nitrogen-containing heterocyclic compound, The recess etching solution according to claim 1 or 2, wherein the nitrogen-containing heterocyclic compound is one or more selected from the group consisting of triazoles, tetrazoles, thiazoles, pyrazoles, imidazoles, and nucleic acid bases.

4. The recess etching solution comprises (B) a nitrogen-containing heterocyclic compound, The recess etching solution according to any one of claims 1 to 3, wherein the nitrogen-containing heterocyclic compound is one or more selected from the group consisting of 1,2,3-triazole, 1,2,4-triazole, 3,5-dimethyl-1,2,4-triazole, 3-amino-1,2,4-triazole, 4-amino-1,2,4-triazole, 3-mercapto-4-methyl-4H-1,2,4-triazole, 1H-benzotriazole, 1H-benzotriazole-1-methanol, 4-methyl-1H-benzotriazole, 2-(2-hydroxy-5-methylphenyl)benzotriazole, 5-methyl-1H-benzotriazole, 3-chloro-1H-benzotriazole, 5-chloro-1H-benzotriazole, 1,2,4-triazole-3-carboxylate methyl, 2-(5-chloro-2-benzotriazol)-6-tert-butyl-p-cresol, and 3-amino-1H-triazole.

5. The recess etching solution comprises (C) an organic solvent, The recess etching solution according to any one of claims 1 to 4, wherein the organic solvent is one or more selected from the group consisting of organic solvents having an HLB (Hydrophile-Lipophile Balance) value of 3 to 15.

6. The recess etching solution comprises (C) an organic solvent, The recess etching solution according to any one of claims 1 to 5, wherein the organic solvent is one or more selected from the group consisting of 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, cyclohexanol, ethylene glycol, propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,2-pentanediol, 1,5-pentanediol, 2,4-pentanediol, diethylene glycol, dipropylene glycol, dibutylene glycol, triethylene glycol, tripropylene glycol, 1,2-hexanediol, 1,6-hexanediol, neopentyl glycol, glycerin, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, acetone, and methyl ethyl ketone.

7. A recess etching solution according to any one of claims 1 to 6, comprising (A) 0.001 to 10% by mass of an organic acid, (B) 0.001 to 5% by mass of a nitrogen-containing heterocyclic compound, and (C) 1 to 99% by mass of an organic solvent.

8. A recess etching solution according to any one of claims 1 to 7, wherein the pH value is in the range of 2.3 to 3.

8.

9. A recess etching method comprising a recess etching step of bringing a recess etching solution according to any one of claims 1 to 8 into contact with the surface of a cobalt-containing metal layer embedded in a via or trench formed in a semiconductor substrate to perform recess etching on the surface of the cobalt-containing metal layer.

10. A method for manufacturing a surface-treated semiconductor substrate, comprising a recess etching step of contacting the surface of a cobalt-containing metal layer embedded in vias or trenches formed on a semiconductor substrate with the recess etching solution described in any one of claims 1 to 8 to perform recess etching on the surface of the cobalt-containing metal layer.

11. A recess etching step in which a recess etching solution according to any one of claims 1 to 8 is brought into contact with the surface of a cobalt-containing metal layer embedded in a via or trench formed on a semiconductor substrate, thereby performing recess etching on the surface of the cobalt-containing metal layer, A step to obtain a semiconductor substrate in which a wiring circuit is constructed by stacking metal wiring layers on the surface of a cobalt-containing metal layer obtained in the recess etching step, A method for manufacturing a semiconductor element, comprising the step of obtaining a semiconductor element by cutting the semiconductor substrate on which the wiring circuit is constructed, obtained in the step of obtaining a semiconductor substrate on which the wiring circuit is constructed, into a predetermined shape.

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