JP7624882B2 - Etching solution, method for producing etching solution, method for treating object, and method for producing ruthenium-containing wiring - Google Patents

Description

The present invention relates to an etching solution, a method for producing the etching solution, a method for treating an object to be treated, and a method for producing ruthenium-containing wiring.

The manufacturing process of semiconductor devices is made up of a variety of multi-stage processing steps. Such processing steps include processes for patterning semiconductor layers and electrodes by etching, etc. In recent years, with the progress of higher integration and higher speed of semiconductor devices, ruthenium (Ru) is sometimes used for wiring, etc. In this case, ruthenium is the target to be etched.

As a ruthenium etching solution for etching ruthenium, for example, one containing orthoperiodic acid as an oxidizing agent has been proposed (Patent Documents 1 and 2). In addition, Patent Document 3 describes a ruthenium etching solution containing orthoperiodic acid and ammonia and having a pH of 4.5 (Table 1, Example A32).

International Publication No. WO 2016/68183 JP 2016-92101 A International Publication No. 2019/138814

In the etching process in the manufacturing process of semiconductor devices, if the etching rate is too low, the etching process takes a long time and is not practical. Furthermore, when an etching solution such as that described in Patent Document 3 is used, there is a risk that toxic ruthenium tetroxide (RuO ₄ ) will be generated by contact between the etching solution and ruthenium.
Therefore, there is a demand for a ruthenium etchant that has an industrially practical etching rate and suppresses the production of ruthenium tetroxide.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an etching solution that is practical for a ruthenium etching process and has a reduced risk of generating ruthenium tetroxide, a method for producing the etching solution, a method for treating a workpiece using the etching solution, and a method for producing a ruthenium-containing wiring.

To solve the above problems, the present invention adopts the following configuration.

The first aspect of the present invention is an etching solution for etching ruthenium, characterized in that it contains orthoperiodic acid and ammonia and has a pH of 8 or more and 10 or less.

The second aspect of the present invention is a method for producing the etching solution, which includes, in this order, a step of mixing a solution containing orthoperiodic acid with ammonia water to prepare a mixed solution, a step of adjusting the pH of the mixed solution to 8 or more and 10 or less, and a step of filtering the mixed solution through a filter.

A third aspect of the present invention is a method for treating an object, comprising the step of etching the object containing ruthenium using the etching solution.

The fourth aspect of the present invention is a method for producing ruthenium-containing wiring, which includes a step of selectively etching the area composed of ruthenium by applying the etching solution to a substrate including a surface area composed of an insulating film and a surface area composed of ruthenium.

The present invention provides an etching solution that is practical for use in ruthenium etching processes and reduces the risk of generating ruthenium tetroxide, a method for producing the etching solution, a method for treating a workpiece using the etching solution, and a method for producing ruthenium-containing wiring.

1 is a schematic diagram showing an example of a substrate having a ruthenium-containing wiring, which is an object to be processed in a recess etching process; FIG. 13 is a schematic diagram showing an example of a wiring substrate after recess etching processing.

(Etching solution)
The etching solution according to a first aspect of the present invention is characterized in that it contains orthoperiodic acid and ammonia, and has a pH of 8 to 10. The etching solution according to this aspect is used for etching ruthenium.

<Orthoperiodic acid>
The etching solution according to this embodiment contains orthoperiodic acid (H ₅ IO ₆ ).

The content of orthoperiodic acid in the etching solution of this embodiment is not particularly limited, but is, for example, 0.05 to 8 mass% relative to the total mass of the etching solution, preferably 0.1 to 7 mass%, more preferably 0.5 to 5 mass%, and even more preferably 0.5 to 3 mass%. When the content of orthoperiodic acid is within the above range, the etching rate for ruthenium is further improved.

<Ammonia>
The etching solution according to this embodiment contains ammonia (NH ₃ ).
The content of ammonia in the etching solution of this embodiment is not particularly limited, and may be set to a content that makes the pH of the etching solution of this embodiment 8 or higher depending on the content of the orthoperiodic acid and the amount of other pH adjusters added as necessary. Preferably, ammonia is used in a content that makes the etching solution of this embodiment have a preferred pH range described below. Examples of the content of ammonia include 5 to 150 parts by mass, preferably 10 to 100 parts by mass, and more preferably 15 to 75 parts by mass, relative to 100 parts by mass of orthoperiodic acid. When the content of ammonia is within the above range, the etching rate for ruthenium is not too low, and the generation of ruthenium tetroxide is reduced.

<Other Ingredients>
The etching solution of the present embodiment may contain other components in addition to the above components, as long as the effects of the present invention are not impaired. Examples of the other components include water, a water-soluble organic solvent, a pH adjuster, a surfactant, and an oxidizing agent.

Furthermore, the etching liquid of the present embodiment may contain a slurry (metal oxide particles) such as that used in a CMP (Chemical Mechanical Polishing) process, or may not contain such a slurry (metal oxide particles).
However, when the etching solution of this embodiment is used for applications such as forming ruthenium wiring by applying the etching solution of this embodiment through a mask to a thin ruthenium film disposed on a substrate, it is preferable that the etching solution does not contain such a slurry (metal oxide particles) from the viewpoint of process stability.
The etching solution of the present embodiment preferably does not contain an abrasive. The abrasive is, for example, a metal oxide particle such as alumina, silica, titania, ceria, or zirconia. The etching solution of the present embodiment preferably does not contain these metal oxide particles.

Water The etching solution of the present embodiment preferably contains water as a solvent for the above components. The water may contain trace components that are inevitably mixed in. The water used in the etching solution of the present embodiment is preferably water that has been subjected to a purification treatment, such as distilled water, ion-exchanged water, or ultrapure water, and it is more preferable to use ultrapure water that is generally used in semiconductor manufacturing.
The content of water in the etching solution of this embodiment is not particularly limited, but is preferably 80 mass% or more, more preferably 90 mass% or more, and even more preferably 94 mass% or more. The upper limit is not particularly limited, but is preferably less than 99.95 mass%, more preferably 99.9 mass% or less, and even more preferably 99.5 mass% or less. The etching solution of this embodiment is preferably an aqueous solution in which the orthoperiodic acid is dissolved in water and adjusted to a pH of 8 to 10 with ammonia.

Water-soluble organic solvent The etching solution of the present embodiment may contain a water-soluble organic solvent within a range that does not impair the effects of the present invention. Examples of the water-soluble organic solvent include alcohols (e.g., methanol, ethanol, ethylene glycol, propylene glycol, glycerin, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, diethylene glycol, dipropylene glycol, furfuryl alcohol, and 2-methyl-2,4-pentanediol), dimethyl sulfoxide, and ethers (e.g., ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and propylene glycol dimethyl ether).

When the etching solution of this embodiment contains a water-soluble organic solvent, the content of the water-soluble organic solvent is preferably 50 mass % or less, more preferably 30 mass % or less, and even more preferably 10 mass % or less, based on the total amount of water and the amount of the water-soluble organic solvent.

The etching solution of the present embodiment may contain a pH adjuster as long as the object of the present invention is not deviated from. In this specification, the term "pH adjuster" refers to a component other than the above-mentioned ammonia that can adjust the pH of the solution.
The amount of the additive is arbitrary and may be selected so as to achieve the pH described below.

As the pH adjuster, an acidic or alkaline compound can be used. Suitable examples of acidic compounds include inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, and their salts, and organic acids such as acetic acid, lactic acid, oxalic acid, tartaric acid, and citric acid, and their salts.

As for the alkaline compound, organic alkaline compounds and inorganic alkaline compounds can be used. Suitable examples of organic alkaline compounds include quaternary ammonium salts such as organic quaternary ammonium hydroxides, and salts of alkylamines such as trimethylamine and triethylamine and their derivatives.

Specific examples of organic quaternary ammonium hydroxides include tetramethylammonium hydroxide (TMAH), bis(2-hydroxyethyl)dimethylammonium hydroxide, tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, methyltriethylammonium hydroxide, trimethyl(hydroxyethyl)ammonium hydroxide, and triethyl(hydroxyethyl)ammonium hydroxide.

Inorganic alkaline compounds include inorganic compounds containing alkali metals or alkaline earth metals and their salts. Examples include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide.

Surfactant The etching solution of the present embodiment may contain a surfactant for the purpose of adjusting the wettability of the etching solution to the object to be treated, etc. As the surfactant, a nonionic surfactant, an anionic surfactant, a cationic surfactant, or an amphoteric surfactant may be used, and these may be used in combination.

Examples of nonionic surfactants include polyalkylene oxide alkyl phenyl ether surfactants, polyalkylene oxide alkyl ether surfactants, block polymer surfactants consisting of polyethylene oxide and polypropylene oxide, polyoxyalkylene distyrene-type phenyl ether surfactants, polyalkylene tribenzyl phenyl ether surfactants, and acetylene polyalkylene oxide surfactants.

Examples of anionic surfactants include alkylsulfonic acids, alkylbenzenesulfonic acids, alkylnaphthalenesulfonic acids, alkyldiphenylethersulfonic acids, fatty acid amidesulfonic acids, polyoxyethylene alkyl ether carboxylic acids, polyoxyethylene alkyl ether acetic acids, polyoxyethylene alkyl ether propionic acids, alkylphosphonic acids, and salts of fatty acids. Examples of "salts" include ammonium salts, sodium salts, potassium salts, and tetramethylammonium salts.

Examples of cationic surfactants include quaternary ammonium salt surfactants and alkylpyridinium surfactants.

Examples of amphoteric surfactants include betaine type surfactants, amino acid type surfactants, imidazoline type surfactants, and amine oxide type surfactants.

These surfactants are generally commercially available. The surfactants may be used alone or in combination of two or more.

Oxidizing Agent The etching solution of the present embodiment may contain other oxidizing agents in addition to the above-mentioned orthoperiodic acid. Examples of the oxidizing agent include transition metal oxides, peroxides, cerium ammonium nitrate, nitrates, nitrites, iodic acid, iodates, periodates, perchlorates, persulfuric acid, persulfates, peracetic acid, peracetates, permanganate compounds, and dichromate compounds.

<pH>
The etching solution of the present embodiment is characterized in that the pH is 8 or more and 10 or less. By adjusting the pH to 8 or more and 10 or less using ammonia as a pH adjuster, a practical etching rate for ruthenium can be maintained and the risk of generating ruthenium tetroxide can be reduced. From the viewpoint of the etching rate, the etching solution of the present embodiment preferably has a pH of 9.5 or less, more preferably a pH of 9.0 or less, and even more preferably a pH of 8.5 or less. From the viewpoint of further reducing the risk of generating ruthenium tetroxide, the etching solution of the present embodiment preferably has a pH of more than 8. The pH range of the etching solution of the present embodiment is preferably a pH of 8 or more and 9.5 or less, more preferably a pH of 8 or more and 9.0 or less, and even more preferably a pH of 8 or more and 8.5 or less. In addition, the pH range of the etching solution of the present embodiment is preferably a pH of more than 8 and 9.5 or less, more preferably a pH of more than 8 and 9.0 or less, and even more preferably a pH of more than 8 and 8.5 or less.
The pH value is a value measured by a pH meter under conditions of room temperature (23° C.) and normal pressure (1 atm).

<Number of particles larger than 100 nm>
In the etching solution of this embodiment, the number of particles larger than 100 nm is preferably 20/mL or less. The number of particles larger than 100 nm is preferably 15/mL or less, more preferably 10/mL or less, and even more preferably 5/mL or less. By making the number of particles larger than 100 nm equal to or less than the upper limit, for example, when the etching solution is applied to a process of selectively etching a region composed of ruthenium for a substrate including a region composed of an insulating film and a region composed of ruthenium on the surface layer as described below, the risk of particles getting into the ruthenium that becomes a recess can be reduced. The number of particles larger than 100 nm in 1 mL of the etching solution can be measured by a light scattering type liquid-borne particle detector. As the light scattering type liquid-borne particle detector, for example, KS-19F manufactured by Rion Co., Ltd. can be mentioned.

<Object to be treated>
The etching solution of this embodiment is used for etching ruthenium, and the target of the etching process is a workpiece containing ruthenium. The workpiece is not particularly limited as long as it contains ruthenium, and examples thereof include a substrate having a ruthenium-containing layer (ruthenium-containing film). The substrate is not particularly limited, and examples thereof include various substrates such as a semiconductor wafer, a glass substrate for a photomask, a glass substrate for a liquid crystal display, a glass substrate for a plasma display, a substrate for an FED (Field Emission Display), a substrate for an optical disk, a substrate for a magnetic disk, and a substrate for a magneto-optical disk. The substrate is preferably a substrate used for manufacturing a semiconductor device. In addition to the ruthenium-containing layer and the substrate base material, the substrate may have various layers and structures, such as metal wiring, a gate structure, a source structure, a drain structure, an insulating layer, a ferromagnetic layer, and a non-magnetic layer, as appropriate. In addition, the top layer of the device surface of the substrate does not need to be a ruthenium-containing layer, and for example, the intermediate layer of a multilayer structure may be a ruthenium-containing layer.
The size, thickness, shape, layer structure, etc. of the substrate are not particularly limited and can be appropriately selected depending on the purpose.

The ruthenium-containing layer is preferably a layer containing ruthenium metal, and more preferably a ruthenium metal film. The thickness of the ruthenium-containing layer on the substrate is not particularly limited and can be appropriately selected depending on the purpose. Examples of the thickness of the ruthenium-containing layer include a range of 1 to 500 nm and 1 to 300 nm.

＜Use＞

The etching solution of this embodiment may be used to perform microfabrication of a ruthenium-containing layer on a substrate, may be used to remove ruthenium-containing deposits attached to a substrate, or may be used to remove impurities such as particles from a workpiece having a ruthenium-containing layer on its surface.

More specifically, the uses of the etching solution of this embodiment include, for example, selective etching of a region composed of ruthenium in a substrate including a region composed of an insulating film and a region composed of ruthenium on the surface layer (recess etching of a ruthenium-containing wiring disposed on a substrate); removal of a ruthenium-containing film from the outer edge of a substrate on which the ruthenium-containing film is disposed; removal of ruthenium-containing material adhering to the back surface of a substrate on which the ruthenium-containing film is disposed; removal of ruthenium-containing material on a substrate after dry etching; removal of ruthenium-containing material on a substrate after CMP processing. However, one embodiment of the etching solution of this embodiment is not used for CMP processing.

<Recess Etching Process>
The etching solution of this embodiment is preferably used for selectively etching the area composed of ruthenium in a substrate including an area composed of an insulating film and an area composed of ruthenium on the surface. A specific example of this process is a recess etching process of a ruthenium-containing wiring arranged on a substrate. The "recess etching process" means a process of forming a recess (recess) in the ruthenium-containing wiring arrangement part on the substrate by etching the ruthenium-containing wiring arranged on the substrate (manufacturing a ruthenium-containing wiring having a recess). In particular, when the number of particles larger than 100 nm contained in the etching solution of this embodiment is 20 pieces/mL or less, the etching solution of this embodiment is suitable for the recess etching process of a ruthenium-containing wiring arranged on a substrate. In the recess etching process of a ruthenium-containing wiring, there is a concern that impurity particles contained in the etching solution will enter the recess, and it is also difficult to remove the impurity particles. By performing the recess etching process using an etching solution having a number of particles larger than 100 nm of 20 pieces/mL or less, such a risk can be reduced.

Figure 1 is a schematic diagram showing an example of a substrate (hereinafter also referred to as a "wiring substrate") having ruthenium-containing wiring, which is the object to be processed in the recess etching process. The wiring substrate 1 has a substrate 3, an underlayer 4 on the substrate, an insulating film 5 having a trench 8 arranged on the underlayer 4, a barrier metal layer 6 arranged along the inner wall of the trench 8, and a ruthenium-containing wiring 7 filled inside the trench. In the wiring substrate 1, the insulating film 5 forms a region constituted by the insulating film. The ruthenium-containing wiring 7 forms a region constituted by ruthenium.

The thickness, shape, layer structure, etc. of the substrate 3 are not particularly limited and can be appropriately selected. Examples of the substrate 3 include various substrates such as a semiconductor wafer, a glass substrate for a photomask, a glass substrate for a liquid crystal display, a glass substrate for a plasma display, a substrate for a field emission display (FED), a substrate for an optical disk, a substrate for a magnetic disk, and a substrate for a magneto-optical disk. Examples of materials constituting the semiconductor substrate include silicon, silicon germanium, and III-V group compounds such as GaAs, as well as any combination thereof.
In addition to the above configuration, the substrate 3 may have any suitable structure. For example, the substrate 3 may have metal wiring, gate electrodes, source electrodes, drain electrodes, insulating layers, ferromagnetic layers, non-magnetic layers, etc. The substrate 3 may have exposed integrated circuit structures, such as interconnect features, such as metal wiring and dielectric materials. Metals and alloys used for the interconnect features include, for example, aluminum, copper-aluminum alloys, copper, titanium, tantalum, cobalt, silicon, titanium nitride, tantalum nitride, and tungsten. The substrate 3 may have layers of silicon oxide, silicon nitride, silicon carbide, and/or carbon-doped silicon oxide.

The ruthenium-containing wiring 7 preferably contains ruthenium alone, a ruthenium alloy, a ruthenium oxide, a ruthenium nitride, or a ruthenium oxynitride. The ruthenium content in the ruthenium-containing wiring 7 is preferably 50 mass% or more, more preferably 60 mass% or more, and even more preferably 80 mass% or more, relative to the total mass (100 mass%) of the ruthenium-containing wiring, and may be 100 mass%. The ruthenium content is, for example, 50 to 90 atomic%. The ruthenium-containing wiring 7 can be formed by a known method, such as CVD or ALD.

The material constituting the underlayer 4 is not particularly limited, and examples thereof include silicon nitride (SiN), silicon carbonitride (SiCN), silicon carbide (SiC), aluminum oxide (AlO _x ), aluminum nitride (AlN), and oxide doped carbon (ODC).

The insulating film 5 can be, for example, an oxide film, a low-k layer, and can be formed, for example, from SiOCH, doped silicon dioxide (with fluorine, carbon and other dopants), spin-on polymers (including organic and silicon-based polymers), porous oxides, etc.

The material constituting the barrier metal layer 6 is not particularly limited, and examples thereof include titanium nitride (TiN), tantalum nitride (TaN), and the like. In the example of FIG. 1, a wiring board 1 having a barrier metal layer 6 is shown, but the wiring board does not have to have a barrier metal layer. In addition, a liner layer (not shown) may be disposed between the barrier metal layer 6 and the ruthenium-containing wiring 7. The material constituting the liner layer is not particularly limited, and examples thereof include Ru-containing and Cu-containing materials.

The method for manufacturing the wiring substrate 1 is not particularly limited, and may include, for example, a method including the steps of forming a base layer on the substrate, forming an insulating film, forming a trench in the insulating film, forming a barrier metal layer on the insulating film, forming a ruthenium-containing film so as to fill the trench, and performing a planarization process on the ruthenium-containing film. In addition, between the steps of forming a barrier metal layer on the insulating film and forming a ruthenium-containing film so as to fill the trench, a step of forming a liner layer on the barrier metal layer may be included.

By performing a recess etching process on the ruthenium-containing wiring 7 in the wiring substrate 1 using the etching solution of this embodiment, a portion of the ruthenium-containing wiring can be removed to form a recess 2 (Figure 2).

Specific methods for the recess etching process include a method of contacting the etching solution of this embodiment with the wiring board 1. The contact method is not particularly limited, and examples include a method of immersing the wiring board 1 in the etching solution of this embodiment contained in a tank (immersion method); a method of ejecting the etching solution of this embodiment onto the wiring board 1 (single-wafer spin method); a method of piling the etching solution of this embodiment on the wiring board 1 (pile method); a method of pouring the etching solution of this embodiment onto the wiring board 1; or a combination thereof.

The processing time of the recess etching process can be appropriately adjusted depending on the etching method, the temperature of the etching solution, etc. The processing time (contact time between the etching solution and the wiring substrate) is not particularly limited, but examples thereof include 0.01 to 30 minutes, 0.1 to 20 minutes, 0.1 to 10 minutes, or 0.15 to 5 minutes.
The temperature of the etching solution during the recess etching process is not particularly limited, but may be, for example, 15 to 75°C, 15 to 65°C, 15 to 65°C, or 15 to 50°C.

After the recess etching process, the wiring substrate obtained by the recess etching process may be treated with a specified chemical solution as necessary. In particular, when a barrier metal layer is disposed on the wiring substrate, as in the case of wiring substrate 1, the components constituting the ruthenium-containing wiring and the components constituting the barrier metal layer may have different solubilities in the etching solution depending on their types. In such a case, it is preferable to use a chemical solution that has better solubility in the barrier metal layer to adjust the degree of dissolution of the ruthenium-containing wiring and the barrier metal layer. From this point of view, it is preferable that the chemical solution has poor dissolving ability for the ruthenium-containing wiring and has good dissolving ability for the material constituting the barrier metal layer.

The chemical solution may be a solution selected from the group consisting of a mixture of ammonia water and hydrogen peroxide water (APM) and a mixture of hydrochloric acid and hydrogen peroxide water (HPM). The composition of APM is preferably within the range of "ammonia water: hydrogen peroxide water: water = 1: 1: 500" to "ammonia water: hydrogen peroxide water: water = 1: 1: 3" (volume ratio). The composition of HPM is preferably within the range of "hydrochloric acid: hydrogen peroxide water: water = 1: 1: 3" to "hydrochloric acid: hydrogen peroxide water: water = 1: 1: 400" (volume ratio).
These preferred composition ratios are intended to mean composition ratios in the case where the ammonia water is 28 mass% ammonia water, the hydrochloric acid is 37 mass% hydrochloric acid, and the hydrogen peroxide solution is 31 mass% hydrogen peroxide solution.
From the viewpoint of the ability to dissolve the barrier metal layer or the ability to remove particles, APM is preferred.

As a method for treating the wiring substrate after recess etching with the chemical solution, a method of contacting the wiring substrate after recess etching with the chemical solution can be mentioned. Examples of the contact method include the same contact method as that mentioned for the recess etching process. Examples of the contact time between the chemical solution and the wiring substrate after recess etching include 0.1 to 10 minutes, or 0.15 to 5 minutes, etc.

In this processing method, the recess etching process and the treatment with the chemical solution may be performed alternately. When performing the processes alternately, it is preferable to perform the cycles of the recess etching process and the treatment with the chemical solution 1 to 10 times each.

<Removal of ruthenium-containing film from the outer edge of the substrate>
The etching solution of the present embodiment may be used to remove the ruthenium-containing film located on the outer edge of a substrate on which the ruthenium-containing film is disposed. For example, the etching solution of the present embodiment may be used to remove the ruthenium-containing film located on the outer edge of a laminate having a substrate and a ruthenium-containing film disposed on one main surface of the substrate.

The ruthenium-containing film preferably contains ruthenium alone, a ruthenium alloy, a ruthenium oxide, a ruthenium nitride, or a ruthenium oxynitride.

The specific method is not particularly limited, but an example is a method in which a chemical solution is supplied from a nozzle so that the etching solution of this embodiment contacts only the ruthenium-containing film on the outer edge of the substrate. Examples of the contact method include the same methods as described above. Examples of the preferred ranges for the contact time and the temperature of the etching solution are the same as those described above.

<Removal of ruthenium-containing material adhering to the back surface of the substrate>
The etching solution of this embodiment may be used to remove ruthenium-containing substances adhering to the back surface of a substrate on which a ruthenium-containing film is disposed. When forming a substrate and a laminate in which a ruthenium-containing film is disposed on one main surface of the substrate, the ruthenium-containing film is formed by sputtering, CVD, or the like. At that time, ruthenium-containing substances may adhere to the surface (back surface) of the substrate opposite to the ruthenium-containing film side. The etching solution of this embodiment may be used to remove ruthenium-containing substances adhering to the back surface of such a laminate.

The specific method is not particularly limited, but an example is a method in which a chemical solution is discharged so that the etching solution of this embodiment contacts only the back surface of the substrate. Examples of contact methods include the same methods as described above. Examples of suitable ranges for the contact time and the temperature of the etching solution are the same as those described above.

The etching solution of this embodiment described above contains orthoperiodic acid as an oxidizing agent, and the pH is adjusted to 8 or more and 10 or less using ammonia, so that a practical etching rate for ruthenium is maintained and the risk of generating ruthenium tetroxide can be reduced. Therefore, by using the etching solution of this embodiment, microfabrication of ruthenium-containing layers and cleaning of ruthenium substrates can be performed safely and effectively.

In addition, when the number of particles larger than 100 nm in the etching solution of this embodiment is 20 particles/mL or less, it can be suitably used for recess etching processing of ruthenium-containing wiring.

(Method of producing etching solution)
The method for producing an etching solution according to the second aspect of the present invention is characterized by including, in this order, a step of mixing a solution containing orthoperiodic acid with aqueous ammonia to prepare a mixed solution, adjusting the pH of the mixed solution to 8 or more and 10 or less (hereinafter also referred to as "step (i)"), and a step of filtering the mixed solution through a filter (hereinafter also referred to as "step (ii)"). The etching solution according to the first aspect is produced by the production method of this embodiment.

<Step (i)>
Step (i) is a step of mixing a solution containing orthoperiodic acid with aqueous ammonia to prepare a mixed liquid, and adjusting the pH of the mixed liquid to 8 or more and 10 or less.

A solution containing orthoperiodic acid (hereinafter also referred to as "orthoperiodic acid solution") can be prepared by dissolving an appropriate amount of orthoperiodic acid in water. The concentration of orthoperiodic acid in the orthoperiodic acid solution can be higher than the concentration of orthoperiodic acid in the final etching solution.

The orthoperiodic acid solution may contain optional components in addition to orthoperiodic acid. Optional components include those listed in the "Other Components" section of "(Etching Solution)" above.

Next, ammonia water is added to the orthoperiodic acid solution and mixed to prepare a mixed solution. Ammonia water that is commercially available can be used, for example, 25 to 30% by mass ammonia water.

The addition of ammonia water to the orthoperiodic acid solution is carried out while measuring the pH of the mixture using a pH meter. At this time, it is preferable to maintain the temperature of the orthoperiodic acid solution and the mixture at 23°C. When the pH of the mixture reaches the desired pH in the range of pH 8 to 10, the addition of ammonia water is terminated.

Next, water is added to the mixture so that the concentration of orthoperiodic acid is the desired concentration. It is preferable to adjust the concentration of orthoperiodic acid so that it is within the suitable concentration range listed in the "Orthoperiodic Acid" section of the "Etching Solution" section above.

This process produces a mixture of orthoperiodic acid solution and ammonia water with a pH of 8 or more and 10 or less.

<Step (ii)>
Step (ii) is a step of filtering the mixture through a filter.

The filter used in this process is not particularly limited, and any filter generally used in the manufacture of chemicals used in semiconductor processes can be used without particular limitation. Examples of filter materials include fluororesins such as polytetrafluoroethylene (PTFE), polyamide resins such as nylon, and polyolefin resins (including high density and ultra-high molecular weight) such as polyethylene and polypropylene (PP). Among these, filters made of polyethylene, polypropylene, polytetrafluoroethylene, or nylon are preferred, polyethylene or polytetrafluoroethylene are more preferred, and polytetrafluoroethylene is particularly preferred.

The pore size of the filter is preferably 100 nm or less, more preferably 50 nm or less, even more preferably 20 nm or less, and particularly preferably 15 nm or less. By using a filter with a pore size equal to or less than the upper limit, even fine particles can be removed. The lower limit of the pore size of the filter is not particularly limited, but from the viewpoint of filtration efficiency, it can be, for example, 0.1 nm or more, or 0.5 nm or more.

Two or more types of filters may be used in combination. When two or more types of filters are used, filters made of different materials and with the same pore size may be used, or filters made of the same material and with different pore sizes may be used, or filters made of different materials and with different pore sizes may be used. For example, the mixed liquid may be filtered using a first filter, and then filtered using a second filter having a smaller pore size than the first filter.

The number of times of filtration of the mixed liquid is not particularly limited and can be any number of times. The number of times of filtration can be, for example, 3 times or more, preferably 5 times or more, more preferably 10 times or more, even more preferably 15 times or more, and particularly preferably 20 times or more, 25 times or more, or 30 times or more. By setting the number of times of filtration to the lower limit or more, it is possible to further reduce fine particles in the mixed liquid. The upper limit of the number of times of filtration of the mixed liquid is not particularly limited, but can be, for example, 50 times or less from the viewpoint of production efficiency.
When filtration is performed using a combination of two or more types of filters, the number of filtrations can be counted as one when the mixed liquid passes through the last filter in the combination of two or more types of filters (hereinafter also referred to as a "filter set").

If the filtration is performed twice or more, it is preferable to filter the mixed liquid by circulating filtration.

This process reduces the number of fine particles in the mixed solution, resulting in a high-quality etching solution.

According to the manufacturing method of this embodiment, a high-quality etching solution can be obtained in which impurity particles (e.g., particles larger than 100 nm) are reduced. The etching solution obtained by the manufacturing method of this embodiment has, for example, 20 particles/mL or less larger than 100 nm. Therefore, the etching solution obtained by the manufacturing method of this embodiment can be suitably used for recess etching of ruthenium-containing wiring arranged on a substrate.

(Method of Processing Object)
A method for processing an object according to a third aspect of the present invention is characterized by comprising the step of etching an object containing ruthenium with the etching solution according to the first aspect.

Examples of the ruthenium-containing object to be treated include those described in "<Object to be treated>" in "(Etching solution)" above, and a preferred example is a substrate having a ruthenium-containing layer. The method for forming the ruthenium-containing layer on the substrate is not particularly limited, and any known method can be used. Examples of such methods include sputtering, chemical vapor deposition (CVD), molecular beam epitaxy (MBE), and atomic layer deposition (ALD). The raw material of the ruthenium-containing layer used to form the ruthenium-containing layer on the substrate is also not particularly limited, and can be appropriately selected depending on the film formation method.

<Step of Etching Object>
This step is a step of etching a ruthenium-containing object to be treated using the etching solution according to the first embodiment, and includes an operation of contacting the object to be treated with the etching solution. The method of etching is not particularly limited, and a known etching method can be used. Examples of such methods include, but are not limited to, a spray method, a dipping method, a puddle method, and the like.
In the spray method, for example, the workpiece is transported or rotated in a predetermined direction, and the etching solution according to the first aspect is sprayed into the space between the workpiece and the etching solution is brought into contact with the workpiece. If necessary, the etching solution may be sprayed onto the workpiece while rotating the substrate using a spin coater.
In the immersion method, the object to be treated is immersed in the etching solution according to the first aspect to bring the etching solution into contact with the object to be treated.
In the puddle method, the etching liquid according to the first embodiment is puddled on the object to be treated, and the object to be treated is brought into contact with the etching liquid.
These etching methods can be appropriately selected depending on the structure, material, etc. of the object to be treated. In the case of the spray method or the puddle method, the amount of the etching liquid supplied to the object to be treated may be an amount that allows the surface of the object to be treated to be sufficiently wetted with the etching liquid.

The purpose of the etching treatment is not particularly limited, and may be fine processing of a ruthenium-containing surface of a workpiece (e.g., a ruthenium-containing layer on a substrate), removal of a ruthenium-containing deposit adhering to the workpiece (e.g., a substrate having a ruthenium-containing layer), or cleaning of a ruthenium-containing surface of a workpiece (e.g., a ruthenium-containing layer on a substrate).
When the purpose of the etching treatment is to finely process the ruthenium-containing surface of the treatment object, the treatment object is usually brought into contact with the etching solution after covering the areas that should not be etched with an etching mask.
When the purpose of the etching treatment is to remove ruthenium-containing deposits adhering to the workpiece, the ruthenium-containing deposits are dissolved by contacting the workpiece with the etching liquid according to the first aspect, and the ruthenium deposits can be removed from the workpiece.
When the purpose of the etching process is to clean a ruthenium-containing surface of a treatment object, the treatment surface is quickly dissolved by contacting the treatment object with the etching solution according to the first aspect, and impurities such as particles adhering to the surface of the treatment object are removed from the surface of the treatment object in a short period of time.
The purpose of the etching process may be the same as that of the recess etching process described above.

The temperature at which the etching process is carried out is not particularly limited, and may be any temperature at which ruthenium dissolves in the etching solution. Examples of etching temperatures include 20 to 60°C. In the case of the spray method, immersion method, and puddle method, the etching rate increases by increasing the temperature of the etching solution, but the processing temperature can be selected appropriately while keeping the compositional change of the etching solution to a minimum and taking into consideration workability, safety, cost, etc.

The time for which the etching process is performed may be appropriately selected depending on the purpose of the etching process, the amount of ruthenium to be removed by etching (e.g., the thickness of the ruthenium-containing layer, the amount of ruthenium deposits, etc.), and the etching process conditions.

Specific examples of the etching process include the processes listed in the "<Application>" section of "(Etching solution)" above. Note that the etching process in one aspect of this embodiment does not include CMP. As the etching process, a process for selectively etching the area composed of ruthenium in a substrate including an area composed of an insulating film and an area composed of ruthenium on the surface layer is preferred. In particular, a recess etching process for ruthenium-containing wiring is preferred.

<Optional step>
The processing method of this embodiment may include any optional step in addition to the above steps, for example, a step of rinsing the processing target object.
After the etching process of the object to be treated in the above-mentioned step, the iodine compound derived from the etching solution according to the first embodiment may adhere to the surface of the object to be treated as residual iodine. Such residual iodine may adversely affect the subsequent process. Therefore, it is preferable to perform a rinsing process in order to remove the residual iodine from the surface of the object to be treated. In addition, the rinsing process can also remove residues of ruthenium-containing substances that are generated on the surface of the object to be treated by the etching process.

The rinse treatment can be carried out by contacting the object to be treated with the rinse liquid. The contacting method is not particularly limited, and examples include a method of immersing the object to be treated in the rinse liquid contained in a tank, a method of spraying the rinse liquid onto the surface of the object to be treated, a method of flowing the rinse liquid onto the surface of the object to be treated, or any combination of these methods.

Examples of rinsing liquids include hydrofluoric acid, hydrochloric acid, hydrogen peroxide, ammonia, tetramethylammonium hydroxide (TMAH), choline, a mixture of hydrofluoric acid and hydrogen peroxide (FPM), a mixture of sulfuric acid and hydrogen peroxide (SPM), a mixture of ammonia water and hydrogen peroxide (APM), a mixture of hydrochloric acid and hydrogen peroxide (HPM), carbon dioxide water, ozone water, hydrogen water, a citric acid solution, sulfuric acid, ammonia water, isopropyl alcohol, a hypochlorous acid solution, ultrapure water, nitric acid, an oxalic acid solution, and acetic acid (including an acetic acid solution).
By carrying out the rinsing process using the above-mentioned rinsing liquid, it is possible to efficiently remove the residue of the ruthenium-containing material that is generated on the surface of the treatment target body by the etching process.

Examples of the acidic rinse liquid include an aqueous citric acid solution (preferably 0.01 to 10 mass % aqueous citric acid solution), hydrofluoric acid (preferably 0.001 to 1 mass % hydrofluoric acid), hydrochloric acid (preferably 0.001 to 1 mass % hydrochloric acid), hydrogen peroxide solution (preferably 0.05 to 6 mass % hydrogen peroxide solution, more preferably 0.3 to 4.5 mass % hydrogen peroxide solution), a mixture of hydrofluoric acid and hydrogen peroxide solution (FPM), a mixture of sulfuric acid and hydrogen peroxide solution (SPM), a mixture of hydrochloric acid and hydrogen peroxide solution (HPM), carbon dioxide solution (preferably 10 to 60 mass ppm carbon dioxide solution), ozone water (preferably is 5 to 60 ppm by mass ozone water), hydrogen water (preferably 0.5 to 20 ppm by mass hydrogen water), sulfuric acid (preferably 1 to 10 mass% sulfuric acid aqueous solution), ammonia water (preferably 0.05 to 6 mass% ammonia water), THAH aqueous solution (preferably 0.05 to 5 mass% TMAH aqueous solution), choline aqueous solution (preferably 0.05 to 5 mass% choline aqueous solution), nitric acid (preferably 0.001 to 1 mass% nitric acid), oxalic acid aqueous solution (preferably 0.01 to 10 mass% oxalic acid aqueous solution), acetic acid (preferably 0.01 to 10 mass% acetic acid aqueous solution, or acetic acid undiluted solution), and the like.
The preferred conditions for FPM, SPM, APM, and HPM are the same as those described above.
Note that hydrofluoric acid, nitric acid, and hydrochloric acid refer to aqueous solutions in which HF, HNO ₃ , and HCl are dissolved in water, respectively. Ozone water, carbon dioxide water, ammonia water, TMAH aqueous solution, choline aqueous solution, and hydrogen water refer to aqueous solutions in which O ₃ , CO ₂ , NH ₃ , methylammonium hydroxide ([(CH ₃ ) ₄ N] ⁺ [OH] ^- ), choline (trimethyl-2-hydroxyethylammonium hydroxide; [(CH ₃ ) ₃ N(CH ₂ ) ₂ OH] ⁺ [OH] ^- ), and H ₂ are dissolved in water, respectively.
These rinse solutions may be mixed together as long as the purpose of the rinse treatment is not impaired. The rinse solution may also contain an organic solvent.

The processing time of the rinse process (contact time between the rinse liquid and the treated object) is not particularly limited, but is, for example, 5 seconds to 5 minutes. The temperature of the rinse liquid during processing is not particularly limited, but is generally, for example, preferably 16 to 60°C, and more preferably 18 to 40°C.

According to the method for treating an object to be treated of this embodiment described above, an etching treatment is performed on the object to be treated using the etching solution according to the first aspect described above, which contains orthoperiodic acid as an oxidizing agent and has a pH adjusted to 8 to 10 with ammonia. This etching solution has a low risk of generating ruthenium tetroxide and has a practical etching rate for ruthenium, so that the etching treatment of ruthenium can be performed safely. Therefore, the processing method of this embodiment can be suitably used for microfabrication of a ruthenium-containing layer formed on a substrate, cleaning of a ruthenium substrate, etc.

(Method of manufacturing ruthenium-containing wiring)
A method for producing a ruthenium-containing wiring according to a fourth aspect of the present invention is characterized in that it includes a step of selectively etching the area composed of ruthenium by applying the etching solution according to the first aspect to a substrate including a surface area composed of an insulating film and a surface area composed of ruthenium.

The manufacturing method of this embodiment can be carried out in the same manner as the method described in "Recess Etching Process" in "(Etching Solution)" above.

(Method of manufacturing semiconductor device)
The method for manufacturing a semiconductor device according to this embodiment is characterized by including a step of etching a target object containing ruthenium with the etching solution according to the first aspect.

The process of etching the workpiece containing ruthenium can be carried out in the same manner as described above in "(Workpiece treatment method)". The workpiece containing ruthenium is preferably a substrate having a ruthenium-containing layer. The substrate may be a substrate that is typically used in the manufacture of semiconductor devices.

<Other steps>
The method for manufacturing a semiconductor device according to the present embodiment may include other steps in addition to the etching process. The other steps are not particularly limited, and include known steps carried out when manufacturing a semiconductor device. Examples of such steps include, but are not limited to, steps for forming each structure such as metal wiring, gate structure, source structure, drain structure, insulating layer, ferromagnetic layer, and non-magnetic layer (layer formation, etching other than the above etching process, chemical mechanical polishing, modification, etc.), resist film formation, exposure step, development step, heat treatment step, cleaning step, inspection step, etc. These other steps can be appropriately carried out before or after the above etching process step, as necessary.

According to the manufacturing method of the semiconductor device of this embodiment described above, an etching process is performed on a processed object using the etching solution according to the first aspect described above, which contains orthoperiodic acid as an oxidizing agent and has a pH adjusted to 8 to 10 with ammonia. Since this etching solution has a low risk of generating ruthenium tetroxide and has a practical etching rate for ruthenium, it is possible to safely perform microfabrication of a ruthenium-containing layer formed on a substrate and cleaning of the substrate. Therefore, the manufacturing method of this embodiment can be suitably used for manufacturing semiconductor devices including ruthenium wiring, etc.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

<Preparation of Etching Solution (1)>
(Examples 1 to 5, Comparative Examples 1 to 3)
2 g of orthoperiodic acid was dissolved in water. Ammonia was added to the orthoperiodic acid solution while measuring the pH at 23° C. using a pH meter, and the solution was adjusted to each pH shown in Table 1. Then, water was added so that the total volume of the solution became 100 mL, thereby preparing the etching solution of each example.

<Etching of object to be processed (1)>
The object to be treated was a ruthenium substrate having a ruthenium film (thickness: 30 nm) formed on a 12-inch silicon substrate by ALD. The etching solution of each example was placed in a beaker, and the ruthenium substrate was immersed in the etching solution of each example at room temperature (23° C.) to perform the etching treatment.

[Evaluation of Etching Rate]
After the etching process was performed by the method described above in "<Etching process of the treated object>", the treated object was removed from the etching solution, and the sheet resistance of the substrate surface was measured. The etching rate of each example was calculated from the sheet resistance. The results are shown in Table 2 as "etching rate".

[Evaluation of ruthenium tetroxide generation]
20 mL of the etching solution of each example was placed in a bottle, and 0.01 g of ruthenium powder was added. Immediately after adding the ruthenium powder, the opening of the bottle was sealed with parafilm and left to stand at room temperature for 3 days. Thereafter, discoloration of the parafilm was visually confirmed and evaluated according to the following evaluation criteria. The results are shown in Table 2 as "discoloration of parafilm." Discoloration of the parafilm indicates the formation of ruthenium tetroxide.
Evaluation criteria: 〇: No discoloration of the Parafilm ×: Discoloration of the Parafilm

As can be seen from Table 2, the Parafilm did not discolor and no generation of ruthenium tetroxide was confirmed in Examples 1 to 5. In addition, the etching rate was maintained within a practical range.
On the other hand, in Comparative Examples 1 and 2, the etching rate was high, but the Parafilm discolored and the generation of ruthenium tetroxide was confirmed. In Comparative Example 3, the generation of ruthenium tetroxide was not confirmed, but the etching rate was low and not practical.
From the above, it can be confirmed that the etching solution of the example to which the present invention is applied makes it possible to etch ruthenium while reducing the risk of generating ruthenium tetroxide.

<Preparation of Etching Solution (2)>
(Examples 6 to 10, Comparative Examples 4 to 6)
2 g of orthoperiodic acid was dissolved in water. While measuring the pH at 23° C. using a pH meter, ammonia was added to the orthoperiodic acid solution to adjust it to each pH shown in Table 3. Thereafter, water was added so that the total volume of the solution became 2000 mL, and the solution was passed through a polytetrafluoroethylene (PTFE) filter having a pore size of 15 nm 30 times to prepare an etching solution for each example. For the etching solution for each example, the number of particles larger than 100 nm per mL of the etching solution was measured using a light scattering type liquid particle detector (KS-19F, manufactured by Rion Co., Ltd.). The results are shown in Table 3 as "number of particles (particles/mL)".
When the number of particles in the etching solution described in Example 6 was measured without passing it through a filter, the measured value was more than 10,000 particles larger than 100 nm per mL of the etching solution.

<Etching of object to be processed (2)>
The etching treatment of the treated object was carried out in the same manner as in <Etching treatment of treated object (1)>, except that the etching solutions of Examples 6 to 10 and Comparative Examples 4 to 6 were used as the etching solutions.

[Evaluation of Etching Rate/Evaluation of Ruthenium Tetroxide Generation]
The etching rate and the generation of ruthenium tetroxide were evaluated in the same manner as above. As a result, in Examples 6 to 10 and Comparative Examples 4 to 6, almost the same results as in Examples 1 to 5 and Comparative Examples 1 to 3 were obtained. That is, in Examples 6 to 10, the etching rate was 1 to 10 nm/min, which was maintained within a practical range. Furthermore, discoloration of the Parafilm was not observed, and the generation of ruthenium tetroxide was not confirmed. On the other hand, in Comparative Examples 4 and 5, the etching rate was higher than in the Examples, but the Parafilm was discolored, and the generation of ruthenium tetroxide was confirmed. Furthermore, in Comparative Example 6, the generation of ruthenium tetroxide was not confirmed, but the etching rate was low and not practical.

1 Wiring substrate 2 Recess 3 Substrate 4 Undercoat layer 5 Insulating film 6 Barrier metal layer 7 Ruthenium-containing wiring

Claims (7)

Contains 0.5 to 3 mass % orthoperiodic acid and ammonia,
The pH is 8 or more and 10 or less,
No slurry or abrasives
An etching solution for etching ruthenium. The etching solution according to claim 1, wherein the number of particles larger than 100 nm contained in the etching solution is 20 particles/mL or less. The etching solution according to claim 1 or 2, wherein the etching process does not fall under a CMP process. The etching solution according to any one of claims 1 to 3, wherein the etching treatment is a treatment in which the etching solution is applied to a substrate including a surface layer having a region formed of an insulating film and a region formed of ruthenium, thereby selectively etching the region formed of ruthenium . A method for producing the etching solution according to any one of claims 1 to 4 ,
a step of mixing a solution containing orthoperiodic acid with ammonia water to prepare a mixed solution, adjusting the pH of the mixed solution to 8 or more and 10 or less , and adjusting the concentration of orthoperiodic acid in the mixed solution to 0.5 to 3 mass % ;
filtering the mixture through a filter;
in that order. A method for treating an object to be treated, comprising the step of etching the object to be treated containing ruthenium with the etching solution according to any one of claims 1 to 4 . A method for producing a ruthenium-containing wiring, wherein the etching treatment is a treatment for selectively etching the region composed of ruthenium by applying the etching solution according to any one of claims 1 to 4 to a substrate including a region composed of an insulating film and a region composed of ruthenium on a surface layer.

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