JP2023127992A - Etching solution, etching method, and method for manufacturing semiconductor integrated circuit - Google Patents

Abstract

To provide an etching solution that suppresses roughness on a copper surface, and also provide an etching method using the etching solution and a method for manufacturing a semiconductor integrated circuit.SOLUTION: There is provided an etching solution for copper or copper alloy etching that contains a chelating agent (A) and is substantially free of hydrogen peroxide. There is also provided an etching method including etching copper or a copper alloy using the etching solution. There is also provided a method for manufacturing a semiconductor integrated circuit, including the step of etching copper or a copper alloy using the etching solution. There is also provided a method for manufacturing a semiconductor integrated circuit, including the etching method.SELECTED DRAWING: None

Description

The present invention relates to an etching solution, an etching method, and a method for manufacturing a semiconductor integrated circuit.

The manufacture of semiconductor integrated circuits consists of various multi-step processing steps. The manufacturing process involves repeated depositions of various materials, lithography, etching, etc. The size of wiring and integrated circuits within semiconductor substrates is becoming smaller year by year, and higher processing precision is required in each process.

Copper interconnects in semiconductor integrated circuits are also becoming finer, but lithography misalignment when forming vertical interconnects (vias) shortens the distance between adjacent interconnects, making short circuits more likely.

To solve this problem, a method called fully self-aligned via (FSAV) has been proposed, in which the copper wiring is slightly etched in advance to ensure distance from adjacent wiring even if lithography misalignment occurs. There is. In order to realize this method, an etching solution that can uniformly etch copper wiring on the order of nanometers is required.

As an etching solution for etching copper, an acidic etching solution containing hydrogen peroxide is disclosed as in Patent Document 1 and Patent Document 2.

Japanese Patent Application Publication No. 2016-135928 JP2020-079444A

However, the etching solution disclosed in Patent Document 1 and Patent Document 2 has a problem in that the etching rate for different directions of each crystal plane of copper is not constant, and unevenness (roughness) occurs on the copper surface.

The present invention has been made in view of such problems, and an object of the present invention is to provide an etching solution that suppresses roughness on a copper surface. Another object of the present invention is to provide an etching method using the etching solution and a method for manufacturing a semiconductor integrated circuit.

Etching solutions containing various components have been studied in the past, but they have not been able to sufficiently suppress roughness on the copper surface. As a result of extensive research, the present inventors discovered an etching solution to be described later, and discovered that this etching solution suppresses roughness on a copper surface.

That is, the gist of the present invention is as follows.
[1] An etching solution for etching copper or copper alloys, which contains a chelating agent (A) and is substantially free of hydrogen peroxide.
[2] The etching solution according to [1], which has a pH of 7 or more.
[3] The etching solution according to [1] or [2], which has a pH of 9 to 12.
[4] The etching solution according to any one of [1] to [3], further comprising a pH adjuster (B).
[5] The etching solution according to any one of [1] to [4], further comprising a surfactant (C).
[6] An etching method comprising etching copper or a copper alloy using the etching solution according to any one of [1] to [5].
[7] The etching method according to [6], in which wiring formed of copper or copper alloy on the surface of the substrate is etched.
[8] The etching method according to [7], wherein the distance between the wirings is 100 nm or less.
[9] A method for manufacturing a semiconductor integrated circuit, comprising a step of etching copper or a copper alloy using the etching solution according to any one of [1] to [5].
[10] A method for manufacturing a semiconductor integrated circuit, comprising the etching method according to any one of [6] to [8].

The etching solution of the present invention suppresses roughness on the copper surface. Further, the etching method of the present invention and the method of manufacturing a semiconductor integrated circuit of the present invention suppress roughness of the copper surface in the etching process.

The present invention will be described in detail below, but the present invention is not limited to the following embodiments, and can be implemented with various changes within the scope of the gist. In addition, when the expression "~" is used in this specification, it is used as an expression including the numerical value or physical property value before and after it.

The etching solution for copper or copper alloy etching of the present invention (hereinafter sometimes referred to as "the etching solution of the present invention") contains a chelating agent (A) and does not substantially contain hydrogen peroxide.

(Chelating agent (A))
The etching solution of the present invention contains a chelating agent (A). The chelating agent (A) is a component that forms a chelate compound with a metal ion and has a function of dissolving the metal, and when the etching solution contains the chelating agent (A), the etching rate is excellent.

Examples of the chelating agent (A) include oxalic acid, malonic acid, succinic acid, glutaric acid, phthalic acid, tartaric acid, citric acid, malic acid, isocitric acid, alanine, arginine, asparagine, aspartic acid, cysteine, glutamine, and glutamic acid. , glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, valine, iminodiacetic acid, hydroxyethyliminodiacetic acid, dihydroxyethylglycine, nitrilotriacetic acid, hydroxyethylethylenediaminetriacetic acid, Ethylenediaminetetraacetic acid, 1,3-propanediaminetetraacetic acid, 1,3-diamino-2-hydroxypropanetetraacetic acid, glycol etherdiaminetetraacetic acid, ethylenediamine, N-methyl-ethylenediamine, 1,2-diaminopropane, 1,3 -Diaminopropane, 1,4-butanediamine, N-methyl-1,3-diaminopropane, diethylenetriaminepentaacetic acid, triethylenetetraaminehexaacetic acid, dicarboxymethylglutamic acid, (S,S)-ethylenediaminedisuccinoacetic acid, 1 -Hydroxyethane-1,1-diphosphonic acid, ethylenediaminetetra (methylenephosphonic acid), gluconic acid, picolinic acid and the like. These chelating agents (A) may be used alone or in combination of two or more. Among these chelating agents (A), aspartic acid, histidine, and ethylenediaminetetraacetic acid are preferred, and aspartic acid and histidine are more preferred, since they have excellent etching rates.

The content of the chelating agent (A) is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, preferably 10% by mass or less, and more preferably 5% by mass or less in 100% by mass of the etching solution. . When the content of the chelating agent (A) is 0.01% by mass or more, the etching solution has an excellent etching rate. When the content of the chelating agent (A) is 10% by mass or less, the etching solution is economically efficient.

(pH adjuster (B))
The etching solution of the present invention preferably further contains a pH adjuster (B) in order to adjust flatness and etching rate.

Examples of the pH adjuster (B) include potassium hydroxide, ammonia, tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide. These pH adjusters (B) may be used alone or in combination of two or more. Among these pH adjusters (B), tetraethylammonium hydroxide and potassium hydroxide are preferred, and tetraethylammonium hydroxide is more preferred, since they have excellent flatness.

The content of the pH adjuster (B) is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, preferably 10% by mass or less, and more preferably 1% by mass or less in 100% by mass of the etching solution. preferable. When the content of the pH adjuster (B) is 0.01% by mass or more, the etching solution has an excellent etching rate. When the content of the pH adjuster (B) is 10% by mass or less, the etching solution is economically efficient.

(Surfactant (C))
The etching solution of the present invention preferably further contains a surfactant (C) because it controls the etched shape by surface adsorption and has excellent flatness.

Examples of the surfactant (C) include alkylbenzene sulfonic acid, polyoxyethylene alkyl ether, polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl ether acetic acid, polyoxyethylene alkyl ether phosphate, and polyoxyethylene alkyl amine. , alkylalkanolamides, alkylammonium salts, alkylamine oxides, and the like. These surfactants (C) may be used alone or in combination of two or more. Among these surfactants (C), dodecylbenzenesulfonic acid, polyoxyethylene alkyl ether, and alkyl ammonium salt are preferable, and polyoxyethylene alkyl ether and alkyl ammonium salt are more preferable, since they are excellent in controlling the etching shape.

The content of the surfactant (C) is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, preferably 1.0% by mass or less, and 0.5% by mass in 100% by mass of the etching solution. % or less is more preferable. When the content of the surfactant (C) is 0.01% by mass or more, the etching solution has excellent etching shape control. When the content of the surfactant (C) is 1.0% by mass or less, the etching solution has excellent low foaming properties.

(Oxidizing agent (D))
The etching solution of the present invention may further contain an oxidizing agent (D) because it oxidizes metal and has an excellent etching rate. However, the oxidizing agent (D) does not substantially contain hydrogen peroxide. Since hydrogen peroxide has a different reaction rate for each crystal orientation of copper, hydrogen peroxide deteriorates the flatness after etching. "Substantially not containing" means that the content is less than 0.01% by mass in 100% by mass of the etching solution, preferably 0.001% by mass or less, and more preferably 0% by mass.

Examples of the oxidizing agent (D) include periodic acid, hypochlorite, and benzoquinone. These oxidizing agents (D) may be used alone or in combination of two or more. Among these oxidizing agents (D), periodic acid and benzoquinone are preferred because they have excellent flatness.

The content of the oxidizing agent (D) is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, preferably 10% by mass or less, and more preferably 1% by mass or less in 100% by mass of the etching solution. . When the content of the oxidizing agent (D) is 0.01% by mass or more, the etching solution has an excellent etching rate. When the content of the oxidizing agent (D) is 10% by mass or less, the etching solution is economically efficient.

(Water (E))
The etching solution of the present invention preferably further contains water (E) because it can dissolve the components (A) to (D) described above and other components described below.

The content of water (E) is preferably 90% by mass or more, more preferably 95% by mass or more, preferably 99.9% by mass or less, and more preferably 99.8% by mass or less in 100% by mass of the etching solution. When the content of water (E) is 90% by mass or more, the solubility of the components (A) to (D) described above and other components described below is excellent. When the content of water (E) is 99.9% by mass or less, the effects of the present invention are easily exhibited.

(other ingredients)
The etching solution of the present invention may contain other components in addition to the chelating agent (A), pH adjuster (B), surfactant (C), oxidizing agent (D), and water (E).

Other ingredients include, for example, ethylene glycol, propylene glycol, polyvinyl alcohol, ethanol, 1-propanol, isopropyl alcohol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, Solvents such as propylene glycol monomethyl ether and propylene glycol monomethyl ether acetate; polymers such as polyacrylic acid, polyacrylamide, dimethyl sulfoxide, polydiallyldimethylammonium chloride, polyethyleneimine, poly(acrylamide-diallyldimethylammonium chloride) copolymer, etc. can be mentioned. These other components may be used alone or in combination of two or more.

The etching solution of the present invention preferably has a pH of 7 or higher, more preferably a pH of 9 to 12, since it provides excellent etching shape.

(mass ratio of components)
The mass ratio of the pH adjuster (B) to the chelating agent (A) (mass of pH adjuster (B)/mass of chelating agent (A)) is preferably 0.01 or more, more preferably 0.1 or more, It is preferably 100 or less, more preferably 10 or less. When the mass ratio of the pH adjuster (B) to the chelating agent (A) is 0.01 or more, the etching solution has excellent flatness. When the mass ratio of the pH adjuster (B) to the chelating agent (A) is 100 or less, the etching solution has an excellent metal etching rate.

The mass ratio of surfactant (C) to chelating agent (A) (mass of surfactant (C)/mass of chelating agent (A)) is preferably 0.01 or more, more preferably 0.1 or more, It is preferably 10 or less, more preferably 5 or less. When the mass ratio of surfactant (C) to chelating agent (A) is 0.01 or more, the etching solution has excellent etching shape control. When the mass ratio of the surfactant (C) to the chelating agent (A) is 10 or less, the etching solution has an excellent metal etching rate.

The mass ratio of surfactant (C) to pH adjuster (B) (mass of surfactant (C)/mass of pH adjuster (B)) is preferably 0.01 or more, and more preferably 0.1 or more. It is preferably 10 or less, more preferably 5 or less. When the mass ratio of the surfactant (C) to the pH adjuster (B) is 0.01 or more, the etching solution has excellent etching shape control. When the mass ratio of the surfactant (C) to the pH adjuster (B) is 10 or less, the etching solution has an excellent metal etching rate.

(Method for manufacturing etching solution)
The etching solution of the present invention can be manufactured by mixing necessary components.
The order of mixing is not particularly limited, and all the components may be mixed at once, or some components may be mixed in advance and then the remaining components may be mixed.
The etching solution of the present invention may be produced by producing a highly concentrated etching solution and then diluting it to a desired concentration.

(Physical properties of etching solution)
The etching rate of the etching solution of the present invention for copper or copper alloy is preferably 0.5 nm/min or more, more preferably 1 nm/min or more, preferably 20 nm/min or less, and more preferably 10 nm/min or less. When the etching rate of the etching solution for copper or copper alloy is 0.5 nm/min or more, the etching solution has excellent productivity in the etching process. When the etching rate of the etching solution for copper or copper alloy is 20 nm/min or less, the etching solution has excellent controllability of the etching process.

The etching rate of the etching solution of the present invention for SiO ₂ is preferably 0.1 nm/min or less, more preferably 0.01 nm/min or less. When the etching rate of the etching solution for SiO ₂ is 0.1 nm/min or less, the etching solution has excellent controllability of the shape after etching.

(Target to be etched with etching solution)
The object to be etched by the etching solution of the present invention is not particularly limited as long as it is copper or a copper alloy, but the etching solution of the present invention is suitable for use in etching fine structures in nanometer units. The etching solution of the present invention is preferably used for semiconductor integrated circuits in which wiring formed of copper or copper alloy is present on the surface of the substrate, and is particularly suitable for semiconductor integrated circuits in which the wirings are present on the surface of the substrate at intervals of 100 nm or less. It is.

The metal species is copper or a copper alloy, with copper being preferred.
The wiring spacing is preferably 100 nm or less, more preferably 50 nm or less.
The semiconductor integrated circuit is preferably a logic circuit, a DRAM circuit, a flash memory circuit, or an image sensor circuit.

(Etching method)
The etching method of the present invention includes a step of etching copper or a copper alloy using the etching solution of the present invention.

As the etching method, a known method can be used, such as a batch method, a single wafer method, and the like.

The temperature during etching is preferably 15° C. or higher, more preferably 20° C. or higher, since the etching rate for copper or copper alloy can be improved.
The temperature during etching is preferably 100° C. or lower, more preferably 80° C. or lower, from the viewpoint of reducing damage to the substrate and etching stability.

(Method for manufacturing semiconductor integrated circuits)
The method for manufacturing a semiconductor integrated circuit of the present invention includes a step of etching copper or a copper alloy using the etching solution of the present invention.
The method of manufacturing a semiconductor integrated circuit of the present invention includes the etching method of the present invention.

(Application)
The etching solution of the present invention and the etching method of the present invention can be suitably used for manufacturing semiconductor integrated circuits, have excellent flatness after etching, and can etch fine structures in nanometer units. It is preferable to use the present invention in a semiconductor integrated circuit in which wiring formed by the method is present on the surface of a substrate, and can be particularly suitably used in a semiconductor integrated circuit in which the wiring is present on the surface of the substrate at intervals of 100 nm or less.

Hereinafter, the present invention will be explained in more detail using examples, but the present invention is not limited to the description of the following examples unless it departs from the gist thereof.

(material)
In the Examples and Comparative Examples, the following components were used.
Component (A1): Aspartic acid Component (A2): Histidine Component (A3): Citric acid Component (D'1): Hydrogen peroxide Component (E1): Water

(pH measurement)
While stirring the etching solutions obtained in Examples and Comparative Examples using a magnetic stirrer, the pH of the etching solutions was measured using a pH meter (model name "D-74", manufactured by Horiba, Ltd.).

(Method of measuring etching rate)
A silicon substrate on which a copper film was formed by plating was cut into 20 mm square pieces. Next, it was immersed for 10 minutes at 25° C. in the etching solutions obtained in Examples and Comparative Examples. After immersion, the substrate was taken out, and the copper concentration in the etching solution after immersion was measured using an ICP emission spectrometer (model name "SPS1700HVR", manufactured by Seiko Instruments Inc.). From the measured copper concentration, the amount of copper eluted in 10 minutes was determined and converted into an etching rate (nm/min).

(Method of measuring flatness)
A patterned substrate on which a 180 nm wide copper wiring was formed was immersed in the etching solutions obtained in Examples and Comparative Examples at 25° C. for the time shown in Table 2 to etch the copper wiring. The substrate after etching was observed with an AFM (atomic force microscope) (model name "MFP-3D", manufactured by Oxford Instruments Co., Ltd.), and the following calculations were performed.

The etching amount (nm) was calculated by determining the cross-sectional shape from the height data of the AFM image.
The root mean square height Sq (nm) was calculated by extracting only the wiring portion from the height data of the AFM image and using the following formula (1).
The maximum height-minimum height Sz (nm) was calculated by extracting only the wiring portion from the height data of the AFM image and using the following formula (2).
In the formula, A represents the reference area, and z represents the height at each measurement point (x, y).

(SEM observation)
A patterned substrate on which a 30 nm wide copper wiring was formed was immersed in the etching solutions obtained in Examples and Comparative Examples at 25° C. for the time shown in Table 2 to etch the copper wiring. The substrate after etching was observed using FE-SEM (model name "S-4800", manufactured by Hitachi High-Tech Corporation), and the shape of the copper wiring after etching was evaluated according to the following criteria.

A: No irregularities of 20 nm or more were observed.
B: Irregularities of 20 nm or more were observed.

[Example 1]
Each component was mixed so that in 100% by mass of the etching solution, component (A1) was 0.11% by mass and component (E1) was the remainder, to obtain an etching solution.
The evaluation results of the obtained etching solution are shown in Table 2.

[Example 2]
An etching solution was obtained in the same manner as in Example 1, except that the types and contents of raw materials were as shown in Table 1.
The evaluation results of the obtained etching solution are shown in Table 2.

[Comparative example 1]
An etching solution was obtained in the same manner as in Example 1, except that the types and contents of raw materials were as shown in Table 1.
The evaluation results of the obtained etching solution are shown in Table 2.

As can be seen from Table 2, the etching solution obtained in Comparative Example 1 has large unevenness after etching, whereas the etching solution obtained in Example 1 and Example 2 has small unevenness after etching. , excellent flatness of copper wiring after etching.

The etching solution of the present invention and the etching method of the present invention can be suitably used for manufacturing semiconductor integrated circuits, have excellent flatness after etching, and can etch fine structures on a nanometer scale. It is preferable to use the present invention in a semiconductor integrated circuit in which wiring formed by the method is present on the surface of a substrate, and can be particularly suitably used in a semiconductor integrated circuit in which the wiring is present on the surface of the substrate at intervals of 100 nm or less.

Claims (10)

An etching solution for etching copper or copper alloys, which contains a chelating agent (A) and is substantially free of hydrogen peroxide. The etching solution according to claim 1, having a pH of 7 or more. The etching solution according to claim 1 or 2, having a pH of 9 to 12. The etching solution according to any one of claims 1 to 3, further comprising a pH adjuster (B). The etching solution according to any one of claims 1 to 4, further comprising a surfactant (C). An etching method comprising the step of etching copper or a copper alloy using the etching solution according to any one of claims 1 to 5. 7. The etching method according to claim 6, wherein wiring formed of copper or copper alloy on the surface of the substrate is etched. The etching method according to claim 7, wherein the spacing between the wirings is 100 nm or less. A method for manufacturing a semiconductor integrated circuit, comprising the step of etching copper or a copper alloy using the etching solution according to any one of claims 1 to 5. A method for manufacturing a semiconductor integrated circuit, comprising the etching method according to any one of claims 6 to 8.