Etching liquid and production method for semiconductor device using same

Abstract

The present invention relates to: an etching liquid that makes it possible to form a favorable etched surface while controlling how much of the surface of a copper-containing metal layer is etched; and a production method for a semiconductor device that uses the etching liquid. This etching liquid is for etching the surface of a copper-containing metal layer and is characterized by including, relative to the total amount of the etching liquid, (A) more than 0.1 but no more than 0.5 mass% of hydrogen peroxide, (B) 0.01–20 mass% of an organic acid that has a lowest acid dissociation constant pKa of at least 2.0, (C) 0.010–0.3 mass% of a nitrogen-containing heteromonocyclic compound, and (D) water, the inorganic acid content being less than 0.1 mass%.

Description

Etching solution and method for manufacturing semiconductor device using same

[0001] The present invention relates to an etching solution for etching the surface of a copper-containing metal layer and a method for manufacturing a semiconductor device using the same.

[0002] In recent years, the miniaturization, weight reduction, and high performance of electronic devices have led to demands for finer and denser metal wiring in semiconductor devices such as semiconductor elements and integrated circuits. This has led to demands for improved metal wiring processing technologies, and in some cases, etching while controlling the etching amount. For example, in multilayer wiring technology, as metal wiring becomes finer and denser, misalignment when connecting upper and lower metal wiring layers increases the likelihood of metal wiring shorts, which is one of the factors reducing yield in semiconductor device manufacturing lines. The Fully Self-Aligned Via (FSAV) process addresses this issue by performing a very small amount of recess etching on the surface of the metal embedded in vias or trenches in the lower metal wiring layer, thereby increasing the distance between adjacent vias or trenches and reducing the likelihood of shorts. Conventionally, dry etching processes have been used after chemical polishing, but dry etching processes have the potential to have an adverse effect on the environment. For this reason, wet etching processes are preferable. Patent Document 1 describes an etching solution containing hydrogen peroxide, a fluorine-free inorganic acid, an organic acid, an amine compound, an azole, and a hydrogen peroxide stabilizer, and having a pH of 2.5 to 5, which is suitable for etching multilayer thin films containing copper and molybdenum layers. Patent Document 2 describes that a copper and copper alloy surface treatment agent containing hydrogen peroxide, a mineral acid, an azole, and an aromatic amine compound can uniformly roughen the copper surface and improve adhesion to dry film resists, etc. Patent Document 3 also describes that an aqueous solution containing hydrogen peroxide, phosphoric acid, and an amino group-containing azole can finish copper and copper alloy surfaces with good adhesion to dry film resists, etc., without roughening the surface. However, with conventional etching solutions, it has been difficult to control the amount of etching and form a desired etched surface on the surface of a copper-containing metal layer.

[0003] International Publication No. 2011 / 099624 Japanese Patent Application Laid-Open No. 2005-133147 Japanese Patent Application Laid-Open No. 2009-299096

[0004] It is desired to provide an etching solution that can form a good etched surface on the surface of a copper-containing metal layer while controlling the etching amount, and a method for manufacturing a semiconductor device using the same.

[0005] The present invention relates to an etching solution and a method for manufacturing a semiconductor device, as described below. [1] An etching solution for etching the surface of a copper-containing metal layer, the etching solution containing, based on the total amount of the etching solution: (A) more than 0.1 to 0.5 mass% hydrogen peroxide, (B) 0.01 to 20 mass% organic acid having a minimum acid dissociation constant pKa of 2.0 or more, (C) 0.010 to 0.3 mass% nitrogen-containing heteromonocyclic compound, and (D) water, and the inorganic acid content is less than 0.1 mass%. [2] The etching solution according to [1] above, wherein component (B) is a carboxylic acid having fewer than three carboxyl groups. [3] The etching solution according to [1] or [2] above, wherein component (B) is a carboxylic acid having fewer than two hydroxyl groups and having one or more carbon atoms not included in the carboxyl groups. [4] The etching solution according to any one of [1] to [3], wherein the component (B) is one or more selected from the group consisting of malic acid, succinic acid, lactic acid, and acetic acid. [5] The etching solution according to any one of [1] to [4], wherein the component (C) is one or more selected from the group consisting of triazoles, tetrazoles, thiazoles, pyrazoles, imidazoles, and nucleic acid bases. [6] The etching solution according to [5], wherein the component (C) is one or more selected from tetrazoles having a substituent at the 5-position. [7] The etching solution according to [6], wherein the component (C) is 5-amino-1H-tetrazole. [8] The etching solution according to any one of [1] to [7], wherein the pH value is less than 4.0. [9] The etching solution according to any one of [1] to [8], wherein the copper etching rate is in the range of 1.5 to 40 nm per minute.

[10] The etching solution according to any one of [1] to [9], wherein the etching rate of copper by the etching solution after dissolving 50 ppm by mass of copper is within ±2 nm per minute of the etching rate of copper by the etching solution before dissolving the copper.

[11] The etching solution according to any one of [1] to

[10] , which is used for recess etching a surface of a copper-containing metal layer embedded in a via or trench formed in a semiconductor substrate.

[12] A method for manufacturing a semiconductor device, comprising the step of contacting the surface of a copper-containing metal layer with the etching solution according to any one of [1] to

[11] above to perform etching.

[13] The method for manufacturing a semiconductor device according to

[12] above, comprising contacting the etching solution with the surface of a copper-containing metal layer embedded in a via or trench formed in a semiconductor substrate to perform recess etching.

[14] A normalized spectral entropy H calculated from 512 pixel x 512 pixel image data obtained by observing an arbitrary 500 nm x 500 nm area of ​​the etched surface of the copper-containing metal layer obtained in the step using a scanning electron microscope. ｎ The method for manufacturing a semiconductor device according to

[12] or

[13] above, wherein the value of the σ is 0.83 or more.

[0006] The etching solution of the present invention is suitable for use as an etching solution for the surface of a copper-containing metal layer. According to a preferred embodiment of the present invention, a good etched surface can be formed while controlling the etching amount. Furthermore, according to a preferred embodiment of the present invention, the use of the etching solution of the present invention suppresses fluctuations in the etching rate even after copper from the copper-containing metal layer to be etched is dissolved, and performance can be maintained.

[0007] 1A is an explanatory diagram of a recess etching process using the etching solution of the present invention, and FIG. 1B is an SEM image of the surface of an evaluation sample after etching treatment in Example 1, FIG. 1B is an SEM image of the surface of an evaluation sample after etching treatment in Comparative Example 2, and FIG. 1C is an SEM image of the surface of an untreated evaluation sample (each observed at a magnification of 100,000 times).

[0008] 1. Etching Solution The etching solution of the present invention is an etching solution for etching the surface of a copper-containing metal layer, and is characterized in that it contains, based on the total amount of the etching solution, (A) more than 0.1 to 0.5 mass% hydrogen peroxide, (B) 0.01 to 20 mass% organic acid having a minimum acid dissociation constant pKa of 2.0 or more, (C) 0.010 to 0.3 mass% nitrogen-containing heteromonocyclic compound, and (D) water, and the inorganic acid content is less than 0.1 mass%.

[0009] Each component will be described below. (A) Hydrogen Peroxide In the present invention, hydrogen peroxide (hereinafter also referred to as component (A)) is a component that functions as an oxidizing agent for copper. There are no particular limitations on component (A), and various grades, such as those for industrial and electronics industries, can be used. In general, it is preferable to use it as an aqueous hydrogen peroxide solution in terms of availability and operability.

[0010] The content of component (A) is in the range of more than 0.1 to 0.5 mass% based on the total amount of the etching solution, preferably more than 0.10 to 0.50 mass%, more preferably 0.12 to 0.50 mass%, even more preferably 0.15 to 0.50 mass%, and particularly preferably 0.20 to 0.50 mass%. In the present invention, by having the content of component (A) within the above range, the amount of etching can be controlled, and a smooth surface can be formed without surface roughness. Furthermore, even after copper is eluted from the copper-containing metal layer to be etched into the etching solution by etching, fluctuations in the etching rate can be suppressed, and the performance of the etching solution can be maintained. Note that when a numerical range is indicated in this specification, the upper and lower limits can be appropriately combined, and the resulting numerical range is also considered to be disclosed.

[0011] (B) Organic Acid with Minimum Acid Dissociation Constant pKa of 2.0 or More In the present invention, an organic acid with a minimum acid dissociation constant pKa of 2.0 or more (hereinafter also referred to as component (B)) has an etching effect on the copper-containing metal layer. Component (B) is not particularly limited as long as it has a minimum acid dissociation constant pKa of 2.0 or more. That is, when a molecule has multiple acidic hydroxyl groups, dissociation occurs stepwise, resulting in multiple pKa values. In this case, component (B) includes an organic acid with a minimum acid dissociation constant pKa of 2.0 or more. The minimum acid dissociation constant pKa of component (B) is preferably 2.5 or more and 7 or less, more preferably 3.0 or more and 6 or less, even more preferably 3.1 or more and 5.5 or less, and particularly preferably 3.2 or more and 5 or less.

[0012] Examples of component (B) include carboxylic acids such as aliphatic carboxylic acids and aromatic carboxylic acids, and amino acids. Among these, carboxylic acids with fewer than three carboxyl groups are preferred, and carboxylic acids with one or two carboxyl groups are more preferred. As the carboxylic acid, aliphatic carboxylic acids and aromatic carboxylic acids are preferred, and more preferred 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, and aliphatic carboxylic acids with 1 to 6 carbon atoms are particularly preferred. Furthermore, as component (B), carboxylic acids with fewer than two hydroxyl groups and one or more carbon atoms not included in the carboxyl groups are more preferred, and carboxylic acids with 0 or 1 hydroxyl group and 1 or 2 carbon atoms not included in the carboxyl groups are even more preferred.

[0013] Examples of aliphatic carboxylic acids include formic acid, acetic acid, propionic acid, lactic acid, glycolic acid, diglycolic acid, butyric acid, hydroxybutyric acid, succinic acid, malic acid, valeric acid, glutaric acid, itaconic acid, adipic acid, caproic acid, propanetricarboxylic acid, enanthic acid, caprylic acid, nonanoic acid, capric acid, lauric acid, myristic acid, palmitic acid, and sorbic acid. These can be used alone or in combination of two or more. Among these, preferred aliphatic carboxylic acids are acetic acid, lactic acid, succinic acid, malic acid, propionic acid, glycolic acid, and combinations thereof.

[0014] Examples of aromatic carboxylic acids include benzoic acid, terephthalic acid, mandelic acid, 2-methylbenzoic acid, 3-methylbenzoic acid, 4-methylbenzoic acid, 2-ethylbenzoic acid, 3-ethylbenzoic acid, 4-ethylbenzoic acid, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, 3-chlorobenzoic acid, 4-chlorobenzoic acid, 2-fluorobenzoic acid, 3-fluorobenzoic acid, 4-fluorobenzoic acid, 2-cyanobenzoic acid, 3-methylbenzoic acid, 4-methylbenzoic acid, 2 ...3-methylbenzoic acid, 4-methylbenzoic acid, 3-methylbenzoic acid, 4-methylbenzoic acid, 3-methylbenzoic acid, 4-methylbenzoic acid, 3-methylbenzoic acid, 4-methylbenzoic acid, 3-methylbenzoic acid, 4-methylbenzo -cyanobenzoic acid, 4-cyanobenzoic 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-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, 5-hydroxy-2-methylbenzoic acid, 4-hydroxy-2-methylbenzoic acid, 4-hydroxy-3-methylbenzoic acid, 2-methoxybenzoic acid, 3-methoxybenzoic acid, 4-methoxybenzoic acid, 3,4-dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2,4,5-trimethylbenzoic acid, 2,4,6-trimethylbenzoic acid, 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, 1-anthracenecarboxylic acid, 2-anthracenecarboxylic acid, 9-anthracenecarboxylic acid, gallic acid, and cinnamic acid. These may be used alone or in combination of two or more.

[0015] As component (B), either an aliphatic carboxylic acid or an aromatic carboxylic acid may be used alone, or an aliphatic carboxylic acid and an aromatic carboxylic acid may be used in combination, but it is more preferable to use one or more aliphatic carboxylic acids.

[0016] The content of component (B) is 0.01 to 20 mass%, preferably 0.1 to 19.5 mass%, more preferably 0.5 to 19.0 mass%, even more preferably 1.0 to 18.5 mass%, and particularly preferably 3.0 to 18.0 mass%, based on the mass of the etching solution, and may be, for example, 3 to 17.78 mass%, or 3.0 to 17.78 mass%, and even more preferably 3.0 to 15.0 mass%. When two or more compounds are used as component (B), the total amount thereof should be within the above range.

[0017] (C) Nitrogen-Containing Heteromonocyclic Compound In the present invention, a nitrogen-containing heteromonocyclic compound (hereinafter also referred to as component (C)) can act as a copper corrosion inhibitor. Component (C) is not particularly limited as long as it contains a nitrogen atom as a heteroatom constituting the ring. Examples thereof include triazoles, tetrazoles, thiazoles, pyrazoles, imidazoles, and nucleic acid bases.

[0018] 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-methyl carboxylate, 2-(5-chloro-2-benzotriazolyl)-6-tertbutyl-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 nucleobases include pyrimidine, uracil, thymine, and cytosine. These can be used alone or in combination of two or more. Among these, tetrazoles are preferred as component (C), and one or more selected from tetrazoles having a substituent at the 5-position are more preferred. In this case, the substituent is preferably a tetrazole having 1 to 10 carbon atoms (C １ ~C １０ ) hydrocarbon groups (e.g., C １ ~C １０ Alkyl group, C１ ~C １０ Alkenyl group, C １ ~C １０ Alkynyl group, C ６ ~C １０ Aryl group, C ７ ~C １０ Alkylaryl group, C ７ ~C １０ arylalkyl group), having 1 to 10 carbon atoms (C １ ~C １０ ) alkoxy group having 7 to 10 carbon atoms (C ７ ~C １０ ) alkylaryloxy group having 2 to 10 carbon atoms (C ２ ~C １０ Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, an octyl group, a nonyl group, and a decyl group. Examples of the alkenyl group include a vinyl group, an allyl group, a propenyl group, an isopropenyl group, a 2-methyl-1-propenyl group, a 2-methylallyl group, and a 2-butenyl group. Examples of the alkynyl group include an ethynyl group, a propynyl group, and a butynyl group. Examples of the aryl group include a phenyl group, a 1-naphthyl group, a 2-naphthyl group, an indenyl group, a biphenyl group, an anthryl group, and a phenanthryl group. Examples of alkylaryl groups include tolyl, xylyl, cumenyl, and mesityl. Examples of arylalkyl groups include benzyl, phenethyl, 1-naphthylmethyl, 2-naphthylmethyl, 1-phenylethyl, phenylpropyl, phenylbutyl, phenylpentyl, phenylhexyl, methylbenzyl, dimethylbenzyl, trimethylbenzyl, ethylbenzyl, methylphenethyl, dimethylphenethyl, and diethylbenzyl. Among these, 5-amino-1H-tetrazole is preferred as component (C).

[0019] The content of component (C) is 0.010 to 0.3 mass%, preferably 0.010 to 0.2 mass%, and more preferably 0.010 to 0.15 mass%, based on the mass of the etching solution. When two or more compounds are used as component (C), the total amount thereof should be within the above range.

[0020] (D) Water The etching solution of the present invention contains water (hereinafter also referred to as component (D)) as a diluent. The water is preferably water from which metal ions, organic impurities, and particles have been removed by distillation, ion exchange treatment, filtration, various adsorption treatments, etc., and pure water or ultrapure water is particularly preferred. The content of component (D), which is the remainder of the etching solution, is preferably 70 mass% or more, more preferably in the range of 75 to 99.9 mass%, and even more preferably 80 to 99.9 mass%, based on the mass of the etching solution.

[0021] (E) Other Components In addition to the components (A), (B), (C), and (D), the etching solution of the present invention may contain additives such as alcohols, phosphonic acid compounds, glycol compounds, surfactants, oxidizing agents, reducing agents, chelating agents, and alkalis that are commonly used in etching copper-containing metal layers, as long as they do not impair the effects of the present invention. However, if inorganic acids (such as sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, etc.) are contained, the surface after etching will become rough, making it difficult to obtain a smooth surface. Therefore, it is preferable that the etching solution of the present invention is substantially free of inorganic acids, and the content of inorganic acids is less than 0.1 mass% based on the mass of the etching solution. The content of inorganic acids is preferably less than 0.05 mass%, more preferably less than 0.03 mass%, and even more preferably less than 0.01 mass% based on the mass of the etching solution.

[0022] According to a preferred aspect of the present invention, the total content of the component (A), the component (B), the component (C), and the 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, still more preferably 98 to 100% by mass, and particularly preferably 99 to 100% by mass, based on the mass of the etching solution.

[0023] The pH of the etching solution of the present invention is not particularly limited, but is preferably less than 4, more preferably 1.0 to 3.8, even more preferably 1.2 to 3.6, and particularly preferably 1.3 to 3.6. A pH adjuster may be added to the etching solution of the present invention as needed to adjust the pH range. Examples of pH adjusters that can be used include potassium hydroxide, lithium hydroxide, cesium hydroxide, triethylamine, ammonia, tetramethylammonium hydroxide, ethanolamine, and 1-amino-2-propanol. One or more pH adjusters can be used.

[0024] The etching solution of the present invention can be prepared by uniformly stirring the components (A) to (D) and, if necessary, other component (E). Note that part or all of the water in component (D) may be added later. Alternatively, a solution containing components (A) to (C), part of component (D), and, if necessary, other component (E) may be prepared in advance, stored, and then diluted with the remainder of component (D) before use.

[0025] The etching rate of the etching solution of the present invention for copper is preferably 1.5 to 40 nm per minute (nm / min), more preferably 1.8 to 40.0 nm / min, and even more preferably 2.0 to 38.0 nm / min, at a treatment temperature of 25°C. If the etching rate is too high, it is difficult to control the amount of etching, and even if the amount of etching is controlled, etching cannot be performed uniformly, making it difficult to obtain a smooth etched surface. Conversely, if the etching rate is too low, the etching process takes a long time, which is undesirable in terms of work efficiency.

[0026] The etching solution of the present invention can uniformly etch the surface of a copper-containing metal layer while controlling the amount of copper etched, thereby forming a good etched surface. Since the etching solution of the present invention can control the amount of copper etched, it can be suitably used when etching a fine region, and can also accommodate miniaturization and high density of metal wiring.

[0027] The etching solution of the present invention can etch the surface of a copper-containing metal layer by contacting the surface with the copper-containing metal layer.

[0028] The temperature at which the etching solution of the present invention is used is not particularly limited, but is, for example, 0 to 70°C, preferably 10 to 50°C, more preferably 20 to 45°C, and even more preferably 25 to 40°C. If the temperature of the etching solution is 10°C or higher, the etching rate is good, and therefore excellent production efficiency can be obtained. On the other hand, if the temperature of the etching solution is 50°C or lower, changes in the solution composition can be suppressed, and etching conditions can be maintained constant. Increasing the temperature of the etching solution increases the etching rate, but the optimum treatment temperature can be determined as appropriate, taking into consideration factors such as minimizing changes in the composition of the etching solution (decomposition of hydrogen peroxide).

[0029] The etching treatment time with the etching solution of the present invention is not particularly limited, but is 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 treatment time may be appropriately selected depending on various conditions such as the surface condition of the copper-containing metal layer to be etched, the concentration of the etching solution, the temperature, and the treatment method.

[0030] The method for bringing the etching solution into contact with the etching target is not particularly limited. For example, a wet method (wet etching method) such as a method in which the etching solution is brought into contact with the etching target by dropping (single wafer spin processing) or spraying the etching solution, or a method in which the etching target is immersed in the etching solution can be used. Either method can be used in the present invention.

[0031] The etching target of the etching solution of the present invention is a copper-containing metal layer. The copper-containing metal layer is preferably a copper layer or a copper alloy layer. The copper content in the copper alloy layer is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may even be 99% by mass or more. The copper-containing metal layer may be, for example, an electrolytic copper foil, an electrolytic copper-plated film, or an electroless copper-plated film, or a combination thereof.

[0032] The thickness (etching depth) of the copper-containing metal layer etched using the etching solution of the present invention is not particularly limited, but is preferably in the range of 2.5 to 50 nm, more preferably 5 to 40 nm, even more preferably 5 to 35 nm, and particularly preferably 5 to 30 nm. The width (wiring width) of the copper-containing metal layer etched using the etching solution of the present invention is not particularly limited, but since the amount of etching can be controlled, it is also possible to accommodate narrower pitches of metal wiring.

[0033] When the etching solution is used multiple times or for a long period of time, fluctuations in the etching rate may occur due to copper dissolution from the copper-containing metal layer. According to a preferred embodiment of the present invention, this phenomenon can be suppressed by adjusting the concentrations of components (A), (B), and (C) to the following: (A) hydrogen peroxide: greater than 0.1 to 0.5 mass%, (B) organic acid having a minimum acid dissociation constant pKa of 2.0 or more: 0.01 to 20 mass%, (C) nitrogen-containing heteromonocyclic compound: 0.010 to 0.3 mass%. According to a preferred embodiment of the present invention, fluctuations in the etching rate are suppressed by adjusting the composition of the etching solution to the above ranges. Even when 50 ppm by mass of copper is dissolved, the difference in etching rate from before dissolution is within ±2 nm / min. This difference is more preferably within ±1.8 nm / min, even more preferably within ±1.5 nm / min, and particularly preferably within ±1.0 nm / min.

[0034] The etching solution of the present invention can be suitably used in processing metal wiring in one step of a method for manufacturing a semiconductor device. According to a preferred embodiment of the present invention, the etching solution can form a good etched surface while controlling the etching amount, and therefore can be suitably used in processing fine metal wiring.

[0035] The above-mentioned good etched surface is an etched surface with minimal unevenness in a microscopic area. The unevenness of an etched surface can be easily evaluated by observing an image under a scanning electron microscope. The method for calculating normalized spectral entropy, which indicates the degree of unevenness from this image, is shown below. From the image data obtained during observation, a 500 nm x 500 nm area of ​​512 pixels x 512 pixels is extracted, and the luminance data Id(l, m) of each pixel is standardized as follows to obtain Is(l, m): where is a pair of natural numbers indicating the position of the pixel. μ and σ are the mean value and standard deviation of the luminance data of 512 pixels × 512 pixels, respectively. Is(l, m) is subjected to a fast Fourier transform to obtain S(k ｌ , k ｍ ) is calculated. ｌ , k ｍ ) is a complex matrix with 512 rows and 512 columns. ｌ , k ｍ ) is a two-dimensional vector whose components are natural numbers proportional to the spatial frequency. ｌ , k ｍ ) to the power spectrum p(k ｌ , k ｍ ) is calculated using the following formula: The sum of the power spectrum is 1 according to the above formula. Therefore, the power spectrum p(k ｌ , k ｍ ) is the spatial frequency (k ｌ , k ｍ The spectral entropy H of an image is calculated using the following formula: Spectral entropy is at its maximum when the light and dark areas in the image are completely randomly arranged. It decreases as regular patterns are formed. The maximum value of spectral entropy, H, as described below, ＭＡＸ The normalized entropy obtained by dividing the actual spectral entropy is used as an index of the brightness and darkness of the scanning electron microscope image, that is, the uneven pattern of the etched surface. The state in which the spectral entropy is maximized is when the spatial frequency (k ｌ , k ｍ) power spectrum p(k ｌ , k ｍ ) has a sum of 1, so the power spectrum p(k ｌ , k ｍ ) is as follows, assuming N=512: Therefore, the maximum value of the spectral entropy H ＭＡＸ will have the following value: Therefore, the normalized spectral entropy H ｎ is expressed as follows: For a completely random image, the normalized spectral entropy H ｎ is 1. A good etched surface with little unevenness in a semiconductor device is one where the normalized spectral entropy H ｎ is an etched surface in which the normalized spectral entropy H ｎ The normalized spectral entropy H is an etched surface in which the normalized spectral entropy H is 0.85 or more. Such an etched surface can be easily realized by using the etching solution of the present invention. ｎ There is no particular upper limit to the value of 1 or less, but if it is 0.97 or more, there is a high possibility that etching has not been performed in the first place or that observation with a scanning electron microscope cannot be performed normally.

[0036] According to one embodiment of the present invention, the etching solution of the present invention can be suitably used as a recess etching solution for performing recess etching on the surface of a copper-containing metal layer embedded in a via or trench formed in a semiconductor substrate.

[0037] 2. Manufacturing Method of Semiconductor Device Next, the manufacturing method of the semiconductor device of the present invention will be described. The manufacturing method of the semiconductor device of the present invention includes a step of contacting the surface of a copper-containing metal layer with the etching solution of the present invention to perform etching.

[0038] The method of contacting the surface of the copper-containing metal layer with the etching solution, the temperature of the etching solution during contact, and the contact time are as described above in "1. Etching Solution." After contacting the copper-containing metal layer with the etching solution and etching, the copper-containing metal layer may be appropriately washed with water, isopropyl alcohol, an aqueous ammonia solution, an aqueous tetramethylammonium hydroxide solution, or the like, as needed. Furthermore, a rust prevention treatment may be performed using an aqueous solution containing a rust inhibitor.

[0039] In one embodiment of the present invention, the process may be a recess etching process in which the etching solution is brought into contact with the surface of a copper-containing metal layer embedded in a via or trench formed in a semiconductor substrate to perform recess etching. In this case, a semiconductor substrate can be manufactured in which recess etching is performed on the surface of a copper-containing metal layer embedded in a via or trench formed in the semiconductor substrate. A wiring circuit can be constructed by stacking additional copper-containing metal layers on this semiconductor substrate.

[0040] 1 is a diagram illustrating the recess etching process using the etching solution of the present invention, in which only the structures necessary for explaining the recess etching process are shown in a schematic manner.

[0041] First, as shown in FIG. 1A , a semiconductor substrate 100 having an interconnect structure is prepared. A via or trench is formed in an interlayer insulating film 20 provided on a substrate 10, and a copper-containing metal layer 30 is embedded in the via or trench. A barrier metal layer 40, such as a titanium layer or titanium nitride layer, may be formed on the inner wall of the via or trench. The semiconductor substrate 100 can be manufactured by a method commonly used in the industry. For example, the semiconductor substrate 100 can be manufactured as follows. First, an interlayer insulating film 20 is formed on the substrate 10. Next, a via or trench is 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 via or trench, if necessary. Next, a copper-containing metal layer 30 is formed to fill the via or trench formed in the interlayer insulating film 20. Finally, CMP (chemical mechanical polishing) is performed as needed to obtain a semiconductor substrate 100 with a smooth top surface.

[0042] Next, as shown in FIG. 1( b ), the surface of the copper-containing metal layer 30 exposed on the upper part of the semiconductor substrate 100 is brought into contact with the etching solution 50 of the present invention.

[0043] There are no particular limitations on the method for bringing the etching solution 50 into contact with the surface of the copper-containing metal layer 30. For example, a method of bringing the etching solution into contact with the surface of the copper-containing metal layer 30 by dropping (single-wafer spin processing) or spraying, or a method of immersing the surface of the copper-containing metal layer 30 in the etching solution can be employed.

[0044] The temperature of the etching solution 50 when it is brought into contact with the copper-containing metal layer 30 is not particularly limited, but is, for example, 0 to 70°C, preferably 25 to 65°C, more preferably 25 to 60°C, and even more preferably 25 to 50°C. If the temperature of the etching solution is 25°C or higher, recess etching can be performed in a shorter time. On the other hand, if the temperature is 50°C or lower, changes in the solution composition can be suppressed, and processing conditions can be maintained constant.

[0045] The time (treatment time) for contacting the copper-containing metal layer 30 with the 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 optimum treatment time can be selected appropriately depending on the method for contacting the copper-containing metal layer with the etching solution, the temperature of the etching solution, etc.

[0046] When recess etching is performed on a copper-containing metal layer using the etching solution of the present invention, the etching rate of the copper-containing metal layer is preferably 1.5 to 40 nm / min, more preferably 1.8 to 40.0 nm / min, and even more preferably 2.0 to 38.0 nm / min.

[0047] 1(c), recess etching can be performed on the surface of the copper-containing metal layer 30. The barrier metal layer 40 in the recess-etched portion may be removed by separate etching in a step after the recess etching, or may be left as it is and used in the next step without being subjected to an etching step.

[0048] The preferred amount of recess etching performed on the copper-containing metal layer (i.e., the depth of the recess formed by performing recess etching on the copper-containing metal layer) is not particularly limited, but is preferably 2.5 to 40 nm, more preferably 5 to 40 nm, and even more preferably 7.5 to 40 nm.

[0049] In one embodiment of the present invention, the method for manufacturing a semiconductor device of the present invention includes: a recess etching step of contacting the surface of a copper-containing metal layer embedded in a via or trench formed in a semiconductor substrate with the above-mentioned etching solution to perform recess etching on the surface of the copper-containing metal layer; and a step of obtaining a semiconductor device having a wiring circuit constructed thereon by stacking metal wiring layers on the surface of the copper-containing metal layer in the surface-treated semiconductor substrate obtained in the above step.

[0050] According to a preferred embodiment of the present invention, a smooth recess-etched surface can be formed in the copper-containing metal wiring in the recess etching step, which makes it possible to prevent short circuits in the metal wiring when a wiring circuit is constructed by stacking metal wiring layers, thereby obtaining a semiconductor device with excellent electrical properties. The metal wiring layer that can be stacked on the surface of the copper-containing metal layer is not particularly limited as long as it contains copper or cobalt and can be electrically connected to the copper-containing metal layer. The metal wiring layer that can be stacked on the surface of the copper-containing metal layer may be one layer or two or more layers.

[0051] Next, the present invention will be explained in more detail using examples and comparative examples, but the present invention is not limited to these examples in any way.

[0052] Examples 1 to 4 (1) Preparation of Etching Solution and Preparation of Copper-Dissolving Etching Solution Etching solutions were prepared by mixing the components in the composition ratios (by mass) shown in Table 1, stirring to make a uniform state. After mixing the components in the composition ratios shown in Table 1, copper (Cu) powder manufactured by Sigma-Aldrich was added in an amount of 50 ppm by mass relative to the total mass of the etching solution, and stirring to make a uniform state, thereby preparing copper-dissolving etching solutions.

[0053] (2) Etching of Copper-Containing Metal Layer As an evaluation sample for the etching solution, a PVD-Cu solid film having a copper layer (thickness: 0.3 μm) on the surface of a substrate manufactured by Filtech Co., Ltd. was used. Next, the surface of the evaluation sample was immersed in the etching solution (25° C.) prepared in (1) above for 1 minute to perform an etching treatment.

[0054] (3) Observation and Evaluation of the Etched Surface of the Copper-Containing Metal Layer The surface of the evaluation sample after etching was observed using a scanning electron microscope (SEM) (apparatus: "SU9000" manufactured by Hitachi High-Technologies Corporation) and evaluated according to the following criteria: ∘: The etched surface of the copper-containing metal layer exhibited smoothness equivalent to that of the untreated layer, or only minute precipitates were observed; ×: Recesses or clearly sized precipitates were observed on the etched surface of the copper-containing metal layer. The results are shown in Table 1. As examples of the surface of the evaluation sample after etching, SEM images (observed at a magnification of 100,000 times) of the etched evaluation sample and the untreated evaluation sample of Example 1 and Comparative Example 2 are shown in Figures 2(a), (b), and (c), respectively. Furthermore, the normalized spectroenthalpy of the etched surface of the copper-containing metal layer was calculated based on the SEM images using the method described above. The results are shown in Table 1.

[0055] (4) Etching Rate of Copper-Containing Metal Layer (Cu E.R.) The etching rate of the copper-containing metal layer was calculated by dividing the difference in copper layer thickness before and after etching by the treatment time. The etching rate of the etching solution before copper dissolution ("Cu 0 ppm") and the etching rate of the etching solution after copper dissolution ("Cu 50 ppm") are shown in Table 1.

[0056] Comparative Examples 1 to 5 Etching solutions were prepared in the same manner as in the Examples, except that the composition ratios (by mass) were as shown in Table 1. A copper-containing metal layer was etched using the evaluation sample. The etching rate of the copper-containing metal layer was calculated in the same manner as in the Examples, and the surface after etching was observed and evaluated.

[0057] The results are shown in Table 1.

[0058]

[0059] As shown in Table 1, by treating a copper-containing metal layer using the etching solution of the present invention, a smooth etched surface can be obtained while controlling the etching rate (Examples 1 to 4). Furthermore, it was shown that the etching solution of the present invention suppresses fluctuations in the etching rate even after copper dissolution. On the other hand, the etching solution of the comparative example did not provide a good etched surface, and the etching rate fluctuated after copper dissolution. As shown by the above results, the etching solution of the present invention has an etching rate within an appropriate range and is excellent at obtaining a smooth etched surface while controlling the etching amount in the treatment of a copper-containing metal layer. The etching solution of the present invention is particularly suitable for applications where control of the etching amount is required and the smoothness of the etched surface is important, such as recess etching. Furthermore, it was shown that the etching rate of the etching solution of the present invention does not fluctuate even after copper dissolution, and its performance is maintained even after copper is dissolved into the etching solution after multiple or long-term use.

[0060] REFERENCE SIGNS LIST 10 Substrate 20 Interlayer insulating film 30 Copper-containing metal layer 40 Barrier metal layer 50 Etching solution 60 Recess etching amount 100 Semiconductor substrate

Claims

1. An etching solution for etching the surface of a copper-containing metal layer, the etching solution containing, based on the total amount of the etching solution, (A) more than 0.1 to 0.5 mass% hydrogen peroxide, (B) 0.01 to 20 mass% of an organic acid having a minimum acid dissociation constant pKa of 2.0 or more, (C) 0.010 to 0.3 mass% of a nitrogen-containing heteromonocyclic compound, and (D) water, and the inorganic acid content is less than 0.1 mass%.

2. The etching solution according to claim 1, wherein the component (B) is a carboxylic acid having less than three carboxyl groups.

3. The etching solution according to claim 1, wherein the component (B) is a carboxylic acid having less than two hydroxyl groups and one or more carbon atoms not included in the carboxyl group.

4. The etching solution according to claim 1, wherein the component (B) is one or more selected from the group consisting of malic acid, succinic acid, lactic acid and acetic acid.

5. The etching solution according to claim 1, wherein the component (C) is at least one member selected from the group consisting of triazoles, tetrazoles, thiazoles, pyrazoles, imidazoles, and nucleic acid bases.

6. The etching solution according to claim 5, wherein the component (C) is one or more selected from tetrazoles having a substituent at the 5-position.

7. The etching solution according to claim 6, wherein the component (C) is 5-amino-1H-tetrazole.

8. The etching solution according to claim 1, having a pH value of less than 4.

0.

9. The etching solution according to claim 1, wherein the etching rate of copper is in the range of 1.5 to 40 nm per minute.

10. The etching solution according to claim 1, wherein the etching rate of copper by the etching solution after dissolving 50 ppm by mass of copper is within the range of ±2 nm per minute of the etching rate of copper by the etching solution before dissolving copper.

11. The etching solution of claim 1 for recess etching a surface of a copper-containing metal layer embedded in a via or trench formed in a semiconductor substrate.

12. A method for manufacturing a semiconductor device, comprising the step of contacting a surface of a copper-containing metal layer with the etching solution according to any one of claims 1 to 11 to perform etching.

13. The method for producing a semiconductor device according to claim 12, wherein the step includes performing recess etching by contacting the etching solution with a surface of a copper-containing metal layer embedded in a via or trench formed in a semiconductor substrate.

14. A normalized spectral entropy H calculated from 512 pixel x 512 pixel image data obtained by observing an arbitrary 500 nm x 500 nm area of ​​the etched surface of the copper-containing metal layer obtained in the above process using a scanning electron microscope. ｎ The method for producing a semiconductor device according to claim 12 , wherein the n-th order is 0.83 or more.

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