TWI861280B - Etching liquid, method for producing etching liquid, method for treating a treated object, and method for producing wiring containing ruthenium - Google Patents

Abstract

An etchant for etching ruthenium, comprising orthoperiodic acid and ammonia, and having a pH of 8 or more and 10 or less. A method for manufacturing the etchant. A method for treating a treated object, comprising the step of etching the treated object containing ruthenium using the etchant. A method for manufacturing wiring containing ruthenium, comprising the step of selectively etching the area composed of ruthenium by applying the etchant to a substrate having a surface layer composed of an insulating film and an area composed of ruthenium.

Description

Etching liquid, method for producing etching liquid, method for treating a treated object, and method for producing wiring containing ruthenium

The present invention relates to an etching solution, a method for manufacturing an etching solution, a method for processing a processed object, and a method for manufacturing wiring containing ruthenium. This application claims priority based on Special Application No. 2019-210515 filed in Japan on November 21, 2019 and Special Application No. 2020-170554 filed in Japan on October 8, 2020, the contents of which are cited in this article.

The manufacturing process of semiconductor devices is composed of various processing steps in multiple stages. These processing steps also include processes that pattern semiconductor layers or electrodes by etching. In recent years, with the high integration and high speed of semiconductor devices, ruthenium (Ru) has been used in wiring, etc. In this case, ruthenium becomes the object of etching.

As a ruthenium etching solution for etching ruthenium, there are proposals, for example, containing orthoperiodic acid as an oxidant (Patent Documents 1 and 2). Patent Document 3 describes a ruthenium etching solution containing orthoperiodic acid and ammonia with a pH of 4.5 (Table 1, Example A32). [Prior Art Document] [Patent Document]

[Patent Document 1] International Publication No. 2016/68183 [Patent Document 2] Japanese Patent Publication No. 2016-92101 [Patent Document 3] International Publication No. 2019/138814

[Problems to be solved by the invention]

In the process of manufacturing semiconductor devices, etching takes a long time and is not practical if the etching rate is too low. In addition, when using an etching solution as described in Patent Document 3, there is a risk of generating toxic ruthenium tetraoxide (RuO ₄ ) when the etching solution comes into contact with ruthenium. Therefore, an etching solution for ruthenium that has an industrially practical etching rate and suppresses the generation of ruthenium tetraoxide is sought. The present invention was completed in view of the above situation, and its subject is to provide an etching solution that is practical in the ruthenium etching step and has a reduced risk of ruthenium tetroxide, a method for manufacturing the aforementioned etching solution, a method for treating a treated object using the aforementioned etching solution, and a method for manufacturing wiring containing ruthenium. [Means for Solving the Problem]

In order to solve the above problems, the present invention adopts the following structure.

The first aspect of the present invention is an etching solution for etching ruthenium, which 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 manufacturing method, which is a manufacturing method of the aforementioned etching solution, and sequentially comprises the following steps: mixing a solution containing original periodic acid with ammonia water to prepare a mixed solution, adjusting the pH of the aforementioned mixed solution to a value between 8 and 10, and filtering the aforementioned mixed solution with a filter.

The third aspect of the present invention is a method for treating an object to be treated, which includes the step of using the aforementioned etching solution to perform etching treatment on the object to be treated containing ruthenium.

The fourth aspect of the present invention is a method for manufacturing wiring containing ruthenium, which includes applying the aforementioned etching solution to a substrate having a surface layer including a region composed of an insulating film and a region composed of ruthenium to selectively etch the region composed of the aforementioned ruthenium. [Effect of the invention]

According to the present invention, an etching solution which is practical in a ruthenium etching step and has a reduced risk of ruthenium tetroxide generation, a method for producing the etching solution, a method for treating an object to be treated using the etching solution, and a method for producing wiring containing ruthenium can be provided.

(Etching fluid)

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

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

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

<Ammonia> The etching solution of the present embodiment contains ammonia (NH ₃ ). The ammonia content in the etching solution of the present embodiment is not particularly limited, as long as the pH of the etching solution of the present embodiment becomes 8 or above, corresponding to the aforementioned original periodic acid content or the amount of other pH adjusters added as needed. Preferably, ammonia is used in a content that becomes a preferred pH range of the etching solution of the present embodiment described later. As the content of ammonia, for example, 5 to 150 parts by mass can be cited, preferably 10 to 100 parts by mass, and more preferably 15 to 75 parts by mass, relative to 100 parts by mass of the original periodic acid. If the ammonia content is within the aforementioned range, the etching rate for ruthenium will not be too low, and the formation of ruthenium tetroxide can be reduced.

<Other components> The etching solution of this embodiment may contain other components in addition to the above components within the scope that does not damage the effect of the present invention. Examples of other components include water, water-soluble organic solvents, pH adjusters, surfactants, and oxidants.

In addition, the etching liquid of the present embodiment may also contain slurry (metal oxide particles) used in the CMP (Chemical Mechanical Polishing) process, or may not contain such slurry (metal oxide particles). However, in the case of using the etching liquid of the present embodiment for the purpose of forming ruthenium wiring through a mask for a ruthenium thin film disposed on a substrate, it is preferably not to contain such slurry (metal oxide particles) from the perspective of process stability. The etching liquid of the present embodiment preferably does not contain abrasives. Abrasives are metal oxide particles such as aluminum oxide, silicon oxide, titanium oxide, barium oxide, zirconium oxide, etc. The etching liquid of the present embodiment preferably does not contain such metal oxide particles.

・Water The etching solution of this embodiment preferably contains water as a solvent for the above-mentioned components. Water may also contain trace components that are inevitably mixed in. The water used in the etching solution of this embodiment is preferably water that has been purified such as distilled water, ion exchange water, and ultrapure water, and it is more preferable to use ultrapure water generally used in semiconductor manufacturing. The water content 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 more preferably 94 mass% or more. The upper limit value is not particularly limited, but is preferably less than 99.95 mass%, more preferably less than 99.9 mass%, and more preferably less than 99.5 mass%. The etching solution of this embodiment is preferably an aqueous solution prepared by dissolving the above-mentioned periodic acid in water and adjusting the pH to 8 or more and 10 or less with ammonia.

・Water-soluble organic solvent The etching solution of this embodiment may contain a water-soluble organic solvent within the range that does not impair the effect of the present invention. Examples of water-soluble organic solvents 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 the present embodiment contains a water-soluble organic solvent, the content of the water-soluble organic solvent is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 10% by mass or less relative to the total amount of water and the water-soluble organic solvent.

・pH adjuster The etching solution of this embodiment may also contain a pH adjuster within the scope of the purpose of the present invention. In this specification, the "pH adjuster" refers to a component other than the aforementioned ammonia, which can adjust the pH of the solution. In addition, the amount of addition is arbitrary, as long as the pH is set to the selected amount described later.

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

As the alkaline compound, an organic alkaline compound and an inorganic alkaline compound can be used. Preferred examples of the organic alkaline compound include quaternary ammonium salts represented by organic quaternary ammonium hydroxide, and salts of alkylamines such as trimethylamine and triethylamine, and derivatives thereof.

Specific examples of the organic quaternary ammonium hydroxide 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.

Examples of inorganic alkaline compounds include inorganic compounds containing alkaline metals or alkaline earth metals and salts thereof, such as lithium hydroxide, sodium hydroxide, potassium hydroxide, amine hydroxide, and cesium hydroxide.

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

Examples of non-ionic surfactants include polyoxyalkylene alkyl phenyl ether surfactants, polyoxyalkylene alkyl ether surfactants, block polymer surfactants composed of polyethylene oxide and polypropylene oxide, polyoxyalkylene distyrenated phenyl ether surfactants, polyalkylene tribenzyl phenyl ether surfactants, acetylene polyoxyalkylene surfactants, and the like.

Examples of anionic surfactants include alkylsulfonic acid, alkylbenzenesulfonic acid, alkylnaphthalenesulfonic acid, alkyldiphenylethersulfonic acid, fatty acid amidesulfonic acid, polyoxyethylene alkyl ether carboxylic acid, polyoxyethylene alkyl ether acetic acid, polyoxyethylene alkyl ether propionic acid, alkylphosphonic acid, 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-based surfactants and alkylpyridinium-based 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. One surfactant may be used alone or two or more surfactants may be used in combination.

・Oxidizing agent The etching solution of this embodiment may contain other oxidizing agents in addition to the above-mentioned orthoperiodic acid. Examples of the oxidizing agent include transition metal oxides, peroxides, ammonium nitrate, nitrates, nitrites, hydroiodic acid, hydroiodates, periodates, perchlorates, persulfuric acid, persulfate, peracetic acid, peracetate, permanganate compounds, dichromate compounds, etc.

<pH> The etching solution of this embodiment is characterized in that the pH is 8 or more and 10 or less. By using ammonia as a pH adjuster, the pH is adjusted to 8 or more and 10 or less, so that a practical etching rate for ruthenium can be maintained and the risk of ruthenium tetroxide generation can be reduced. The etching solution of this embodiment is preferably 9.5 or less in terms of etching rate, more preferably 9.0 or less, and even more preferably 8.5 or less. The etching solution of this embodiment is preferably higher than pH 8 in terms of further reducing the risk of ruthenium tetroxide generation. As the pH range of the etching solution of this embodiment, the pH is preferably 8 or more and 9.5 or less, the pH is more preferably 8 or more and 9.0 or less, and even more preferably 8 or more and 8.5 or less. In addition, the pH range of the etching solution of this embodiment is preferably greater than pH 8 and less than pH 9.5, more preferably greater than pH 8 and less than pH 9.0, and even more preferably greater than pH 8 and less than pH 8.5. The aforementioned pH value is a value measured with a pH meter under normal temperature (23°C) and normal pressure (1 atmosphere).

<Number of particles larger than 100nm> The number of particles larger than 100nm in the etching solution of this embodiment is preferably 20 particles/mL or less. The number of particles larger than 100nm is preferably 15 particles/mL or less, more preferably 10 particles/mL or less, and even more preferably 5 particles/mL or less. By setting the number of particles larger than 100nm to below the above upper limit, for example, in the case of applying a process of selectively etching the area composed of ruthenium for a substrate including an area composed of an insulating film and an area composed of ruthenium on the surface as described later, the risk of particles entering the ruthenium that forms a recess can be reduced. The number of particles larger than 100nm in 1mL of the etching solution can be measured by a light scattering liquid particle detector. An example of the aforementioned light scattering liquid particle detector is KS-19F manufactured by RION Co., Ltd.

<Processed object> The etching liquid of this embodiment is used to etch ruthenium, and the processed object containing ruthenium is the etching processing object. The processed object is not particularly limited as long as it contains ruthenium, but an example is a substrate having a ruthenium-containing layer (ruthenium-containing film). The aforementioned substrate is not particularly limited, and examples are various substrates such as semiconductor wafers, glass substrates for masks, glass substrates for liquid crystal displays, glass substrates for plasma displays, substrates for FED (Field Emission Display), substrates for optical disks, substrates for magnetic disks, and substrates for optical magneto-disks. The aforementioned substrate is preferably a substrate used to manufacture semiconductor devices. In addition to the ruthenium-containing layer and the substrate base material, the aforementioned substrate may also have various layers or structures, such as metal wiring, gate structure, source structure, drain structure, insulating layer, ferromagnetic layer and non-magnetic layer. In addition, the top layer of the device surface of the substrate does not necessarily have to be a ruthenium-containing layer. For example, the middle layer of the multi-layer structure may also be a ruthenium-containing layer. The size, thickness, shape, layer structure, etc. of the substrate are not particularly limited and can be appropriately selected according to 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 according to the purpose. The thickness of the ruthenium-containing layer is, for example, in the range of 1 to 500 nm or 1 to 300 nm.

＜Application＞

The etching solution of this embodiment can also be used for micro-processing of a ruthenium-containing layer of a substrate, can also be used for removing ruthenium-containing deposits attached to a substrate, and can also be used for removing impurities such as particles from a processed object having a ruthenium-containing layer on its surface.

More specifically, the use of the etching liquid of this embodiment is, for example, to selectively etch the region composed of ruthenium in a substrate whose surface layer includes a region composed of an insulating film and a region composed of ruthenium (dig-in etching of ruthenium-containing wiring arranged on the substrate); to remove the ruthenium-containing film at the outer edge of the substrate arranged with the ruthenium-containing film; to remove the ruthenium-containing material attached to the back of the substrate arranged with the ruthenium-containing film; to remove the ruthenium-containing material on the substrate after dry etching; to remove the ruthenium-containing material on the substrate after CMP treatment, etc. However, in this embodiment, one aspect of the etching liquid is not used for CMP treatment.

"Dig-in etching treatment" As the purpose of the etching liquid of this embodiment, it is preferred to selectively etch the area composed of ruthenium in a substrate whose surface layer includes an area composed of an insulating film and an area composed of ruthenium. As a specific example of this treatment, a dig-in etching treatment of a wiring containing ruthenium arranged on a substrate is given. The so-called "dig-in etching treatment" means a treatment in which a concave portion (dig-in) is formed in the arrangement portion of the ruthenium-containing wiring on the substrate by etching the wiring containing ruthenium arranged on the substrate (manufacturing a wiring containing ruthenium having a concave portion). In particular, when the number of particles larger than 100 nm contained in the etching solution of the present embodiment is 20 or less per mL, the etching solution of the present embodiment is suitable for the digging etching process of the wiring containing ruthenium disposed on the substrate. The digging etching process of the wiring containing ruthenium has the concern that the impurity particles contained in the etching solution enter the recessed part, and it is also difficult to remove the impurity particles. By using the etching solution with the number of particles larger than 100 nm being 20 or less per mL for the digging etching process, such risks can be reduced.

FIG1 is a schematic diagram showing an example of a substrate having wiring containing ruthenium (hereinafter also referred to as a "wiring substrate") which is a workpiece during a digging etching process. The wiring substrate 1 has a substrate 3, a base layer 4 on the substrate, an insulating film 5 having a trench 8 disposed on the base layer 4, a barrier metal layer 6 disposed along the inner wall of the trench 8, and wiring containing ruthenium 7 filled in the trench. In the wiring substrate 1, the insulating film 5 forms a region composed of an insulating film. The wiring containing ruthenium 7 forms a region composed of ruthenium.

The thickness, shape and layer structure of the substrate 3 are not particularly limited and can be appropriately selected. Examples of the substrate 3 include various substrates such as semiconductor wafers, glass substrates for masks, glass substrates for liquid crystal displays, glass substrates for plasma displays, substrates for FED (Field Emission Display), substrates for optical disks, substrates for magnetic disks, and substrates for magneto-optical disks. Examples of materials constituting semiconductor substrates include III-V compounds such as silicon, silicon germanium and GaAs, and any combination thereof. In addition to the above-mentioned structure, the substrate 3 can also have any structure as appropriate. For example, the substrate 3 can also have metal wiring, a gate electrode, a source electrode, a drain electrode, an insulating layer, a ferromagnetic layer, a non-magnetic layer, etc. The substrate 3 may also have an exposed integrated circuit structure, such as interconnections of metal wiring and dielectric materials. Examples of metals and alloys used in the interconnections are aluminum, copper-aluminum alloy, copper, titanium, tantalum, cobalt, silicon, titanium nitride, tantalum nitride, and tungsten. The substrate 3 may also have a layer of silicon oxide, silicon nitride, silicon carbide, and/or carbon-doped silicon oxide.

The ruthenium-containing wiring 7 preferably includes a ruthenium monomer, 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, more preferably 80 mass % or more, and may also be 100 mass %, relative to the total mass of the ruthenium-containing wiring (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, ALD, etc.

The material constituting the base layer 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 or a low-k layer, and can be formed by, for example, SiOCH, doped silicon dioxide (fluorine, carbon, and other dopants), spin-coated polymer (including organic and silicon-based polymers), porous oxide, etc.

The material constituting the barrier metal layer 6 is not particularly limited, and examples thereof include titanium nitride (TiN), tantalum nitride (TaN), etc. FIG. 1 shows a wiring substrate 1 having a barrier metal layer 6, but the wiring substrate may not have a barrier metal layer. In addition, an underlayer not shown may be arranged between the barrier metal layer 6 and the wiring 7 containing ruthenium. The material constituting the underlayer is not particularly limited, and examples thereof include Ru-containing materials and Cu-containing materials.

The manufacturing method of the wiring board 1 is not particularly limited, and for example, a method including the following steps: forming a base layer on a substrate, forming an insulating film, forming a trench on the insulating film, forming a barrier metal layer on the insulating film, forming a ruthenium-containing film in a manner that fills the trench, and performing a planarization treatment on the ruthenium-containing film. In addition, between the step of forming a barrier metal layer on the insulating film and the step of forming a ruthenium-containing film in a manner that fills the trench, a step of forming an underlayer on the barrier metal layer may be included.

By using the etching solution of this embodiment to perform a digging etching process on the wiring 7 containing ruthenium in the wiring substrate 1, a part of the wiring containing ruthenium can be removed to form a recess 2 (FIG. 2).

As a specific method of the digging etching process, there is exemplified a method of bringing the etching liquid of the present embodiment into contact with the wiring substrate 1. The contact method is not particularly limited, and examples thereof include a method of immersing the wiring substrate 1 in the etching liquid of the present embodiment placed in a tank (immersion method); a method of spraying the etching liquid of the present embodiment on the wiring substrate 1 (single-wafer spinning method); a method of covering the wiring substrate 1 with the etching liquid of the present embodiment (liquid covering method); a method of flowing the etching liquid of the present embodiment on the wiring substrate 1; or a combination thereof.

The processing time of the dig-in etching process can be appropriately adjusted according to the etching method and the temperature of the etching solution. The processing time (contact time of the etching solution and the wiring substrate) is not particularly limited, but examples 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 dig-in etching process is not particularly limited, but examples include 15 to 75°C, 15 to 65°C, 15 to 65°C, or 15 to 50°C.

Furthermore, after the deep etching process, a specific chemical solution may be used, if necessary, to process the wiring board obtained by the deep etching process. In particular, when a barrier metal layer is arranged on the wiring board as in the wiring board 1, the components constituting the wiring containing ruthenium and the components constituting the barrier metal layer may have different solubility in the etching solution depending on their types. In such cases, it is preferable to use a chemical solution with better solubility in the barrier metal layer to adjust the solubility of the wiring containing ruthenium and the barrier metal layer. Based on these aspects, the aforementioned chemical solution is preferably a chemical solution that lacks solubility in the wiring containing ruthenium and has excellent solubility in the substances constituting the barrier metal layer.

As the aforementioned chemical solution, for example, a solution selected from the group consisting of a mixture of ammonia water and hydrogen peroxide (APM) and a mixture of hydrochloric acid and hydrogen peroxide (HPM). The composition of APM is preferably in the range of, for example, "ammonia water: hydrogen peroxide: water = 1:1:500" to "ammonia water: hydrogen peroxide: water = 1:1:3" (volume ratio). The composition of HPM is preferably in the range of, for example, "hydrochloric acid: hydrogen peroxide: water = 1:1:3" to "hydrochloric acid: hydrogen peroxide: water = 1:1:400" (volume ratio). The description of the preferred composition ratios is intended to be a composition ratio of 28% by mass of ammonia water, 37% by mass of hydrochloric acid, and 31% by mass of hydrogen peroxide. Based on the dissolution energy of the barrier metal layer or the particle removal performance, APM is preferred.

As a method of using the above-mentioned chemical solution to process the wiring substrate after the digging etching process, an example is a method of bringing the above-mentioned chemical solution into contact with the wiring substrate after the digging etching process. As an example of the contact method, it is the same method as the contact method exemplified in the above-mentioned digging etching process. As an example of the contact time between the above-mentioned chemical solution and the wiring substrate after the digging etching process, it is, for example, 0.1 to 10 minutes or 0.15 to 5 minutes.

In this treatment method, the digging etching treatment and the treatment with the above-mentioned chemical solution can also be performed alternately. In the case of alternately performing, the digging etching treatment and the treatment with the above-mentioned chemical solution are preferably performed 1 to 10 times each.

"Removal of ruthenium-containing film on the outer edge of substrate" The etching liquid of this embodiment can also be used to remove the ruthenium-containing film on the outer edge of a substrate on which the ruthenium-containing film is disposed. The etching liquid of this embodiment can also be used, for example, in a composite body having a substrate and a ruthenium-containing film disposed on a main surface on one side of the substrate to remove the ruthenium-containing film located on the outer edge.

The ruthenium-containing film preferably includes a ruthenium monomer, 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 of supplying the chemical solution from the nozzle in such a manner that the etching solution of the present embodiment contacts only the ruthenium-containing film on the outer edge of the substrate. The contact method is exemplified by the same method as described above. The preferred range of the contact time and the temperature of the etching solution is exemplified by the same method as described above.

《Removal of ruthenium-containing substances attached to the back side of a substrate》 The etching liquid of this embodiment can also be used to remove ruthenium-containing substances attached to the back side of a substrate on which a ruthenium-containing film is disposed. When forming a substrate and a laminate having a ruthenium-containing film disposed on one main surface of the substrate, the ruthenium-containing film is formed by sputtering and CVD. At this time, ruthenium-containing substances may be attached to the surface of the substrate opposite to the ruthenium-containing film side (on the back side). In order to remove ruthenium-containing substances attached to the back side of such a laminate, the etching liquid of this embodiment can also be used.

The specific method is not particularly limited, but an example is a method of spraying the chemical solution so that the etching solution of this embodiment contacts only the back side of the substrate. The contact method is exemplified by the same method as described above. The preferred ranges of the contact time and the temperature of the etching solution are exemplified by the same method as described above.

According to the etching solution of the present embodiment described above, since it contains orthoperiodic acid as an oxidant and is adjusted to a pH of 8 or more and 10 or less by ammonia, it is possible to maintain a practical etching rate for ruthenium and reduce the risk of ruthenium tetroxide generation. Therefore, by using the etching solution of the present embodiment, micro-processing of ruthenium-containing layers or cleaning of ruthenium substrates can be performed safely and appropriately.

Furthermore, when the number of particles larger than 100 nm in the etching solution of this embodiment is 20/mL or less, it can be suitably used for the deep etching process of wiring containing ruthenium.

(Method for producing etching liquid) The method for producing etching liquid of the second embodiment of the present invention is characterized by comprising the following steps in sequence: mixing a solution containing original periodic acid with aqueous ammonia to prepare a mixed solution, adjusting the pH of the mixed solution to a value between 8 and 10 (hereinafter also referred to as "step (i)"), and filtering the mixed solution with a filter (hereinafter also referred to as "step (ii)"). The etching liquid of the first embodiment is produced by the production method of this embodiment.

<Step (i)> Step (i) is a step of mixing a solution containing periodic acid with aqueous ammonia to prepare a mixed solution, and adjusting the pH of the mixed solution to a value between 8 and 10.

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 set to be higher than the concentration of orthoperiodic acid in the final etching solution.

The orthoperiodic acid solution may contain any component other than orthoperiodic acid. Examples of such optional components include the components listed in the "<Other components>" of the above-mentioned "(etching solution)".

Next, ammonia water is added to the original periodic acid solution and mixed to prepare a mixed solution. Ammonia water available on the market can be used, and ammonia water with a concentration of, for example, 25-30% by mass can also be used.

The addition of ammonia water to the original periodic acid solution is carried out while measuring the pH of the mixed solution with a pH meter. At this time, the temperature of the original periodic acid solution and the mixed solution is preferably maintained at 23°C. When the pH of the mixed solution reaches the desired pH in the range of pH 8 or more and pH 10 or less, the addition of ammonia water is terminated.

Next, water is added to the mixed solution in such a way that the concentration of the original periodic acid becomes the desired concentration. The concentration of the original periodic acid is preferably adjusted to the preferred concentration range given in the "Original Periodic Acid" item in the "(Etching Solution)" above.

Through this step, a mixed solution of the original periodic acid solution and ammonia water with a pH of more than 8 and less than 10 can be obtained.

<Step (ii)> Step (ii) is a step of filtering the aforementioned mixed solution with a filter.

The filter used in this step is not particularly limited, and filters generally used in the manufacture of chemical solutions used in semiconductor processes can be used without particular restrictions. Examples of filter materials include fluororesins such as polytetrafluoroethylene (PTFE), polyamide resins such as nylon, polyolefin resins such as polyethylene and polypropylene (PP) (including high-density and ultra-high molecular weight), etc. Among them, polyethylene, polypropylene, polytetrafluoroethylene or nylon are preferred, polyethylene or polytetrafluoroethylene is 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, still more preferably 20 nm or less, and particularly preferably 15 nm or less. By using a filter with a pore size below the aforementioned upper limit, fine particles can also be removed. The lower limit of the pore size of the filter is not particularly limited, but based on the viewpoint of filtering efficiency, it can be, for example, 0.1 nm or more or 0.5 nm or more.

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

The number of times the mixed solution is filtered is not particularly limited and can be any number. The number of times of filtering can be, for example, 3 times or more, preferably 5 times or more, more preferably 10 times or more, and 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 filtering to above the above lower limit, the fine particles in the mixed solution can be further reduced. The upper limit of the number of times the mixed solution is filtered is not particularly limited, but based on the viewpoint of manufacturing efficiency, it can be, for example, 50 times or less. In the case of filtering by combining two or more filters, the number of filtering is calculated as 1 time when the mixed solution passes through the last filter of the combined two or more filters (hereinafter also referred to as "filter set").

If the filtration times are more than 2 times, it is better to filter the mixed liquid by circulating filtration.

Through this step, the fine particles in the mixed solution can be reduced, and a high-quality etching solution can be obtained.

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

(Processing method of the processed object) The processing method of the third aspect of the present invention is characterized by comprising the step of etching the processed object containing ruthenium using the etching solution of the first aspect.

Examples of ruthenium-containing processed objects are the same as those described in the "<Processed Object>" item in the above "(Etching Solution)", preferably a substrate having a ruthenium-containing layer. The method for forming the ruthenium-containing layer on the substrate is not particularly limited, and a known method can be used. Examples of such methods include sputtering, chemical vapor deposition (CVD: Chemical Vapor Deposition), molecular beam epitaxy (MBE: Molecular Beam Epitaxy) and atomic layer deposition (ALD: Atomic layer deposition). The raw materials of the ruthenium-containing layer used when forming the ruthenium-containing layer on the substrate are also not particularly limited, and can be appropriately selected according to the film formation method.

<Step of etching the object> This step is a step of etching the object containing ruthenium using the etching solution of the first embodiment, and includes an operation of bringing the etching solution into contact with the object. The etching method 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, an immersion method, and a coating method. The spray method is, for example, to transport and rotate the object in a specific direction, spray the etching solution of the first embodiment in the space, and bring the etching solution into contact with the object. If necessary, a rotary coater can be used to spray the etching solution while rotating the substrate. The immersion method is to immerse the object to be processed in the etching liquid of the first embodiment so that the etching liquid contacts the object to be processed. The coating method is to coat the etching liquid of the first embodiment on the object to be processed so that the object to be processed contacts the etching liquid. These etching treatment methods can be appropriately selected according to the structure or material of the object to be processed. In the case of the spray method or the coating method, the amount of the etching liquid supplied to the object to be processed is sufficient as long as the surface to be processed in the object to be processed is fully wetted by the etching liquid.

The purpose of etching treatment is not particularly limited. It can be fine processing of the ruthenium-containing surface of the object to be processed (such as the ruthenium-containing layer on the substrate), or it can be the removal of ruthenium-containing attachments attached to the object to be processed (such as a substrate with a ruthenium-containing layer), or it can be the cleaning of the ruthenium-containing surface of the object to be processed (such as the ruthenium-containing layer on the substrate). The purpose of etching treatment is the fine processing of the ruthenium-containing surface of the object to be processed. Usually, the part that should not be etched is covered by an etching mask to make the object to be processed contact with the etching liquid. In the case where the purpose of etching treatment is to remove ruthenium-containing attachments attached to the object to be processed, the ruthenium-containing attachments are dissolved by bringing the etching solution of the first embodiment into contact with the object to be processed, and the ruthenium attachments can be removed from the object to be processed. In the case where the purpose of etching treatment is to clean the surface of the object to be processed containing ruthenium, the etching solution of the first embodiment is brought into contact with the object to be processed, and the aforementioned surface to be processed is quickly dissolved, so that impurities such as particles attached to the surface of the object to be processed are removed from the surface of the object to be processed in a short time. In addition, the purpose of etching treatment is the same as the aforementioned "dig-in etching treatment".

The temperature for etching is not particularly limited, as long as ruthenium is soluble in the aforementioned etching solution. The temperature for etching is, for example, 20 to 60°C. In any of the spray method, immersion method, and coating method, the etching rate is increased by increasing the temperature of the etching solution, but the processing temperature is appropriately selected in consideration of suppressing the composition change of the etching solution to a small extent or considering workability, safety, cost, etc.

The etching time can be appropriately selected according to the purpose of the etching, 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 conditions.

As a specific example of etching treatment, the treatment exemplified in the item "<Application>" in the above-mentioned "(Etching liquid)" is given. In addition, the etching treatment of one aspect of the present embodiment does not include CMP treatment. As etching treatment, it is preferred that in a substrate whose surface layer includes a region composed of an insulating film and a region composed of ruthenium, the region composed of ruthenium is selectively etched. In particular, it is preferred that the trench etching treatment of the wiring containing ruthenium is performed.

<Optional Step> The processing method of this embodiment may include any steps in addition to the above steps. An example of an optional step is a step of performing a cleaning treatment on the object to be processed. After the object to be processed is etched in the above steps, there may be iodine compounds from the etching solution of the first state attached to the surface of the object to be processed as residual iodine. Such residual iodine may adversely affect subsequent processes. Therefore, in order to remove the residual iodine from the surface of the object to be processed, it is better to perform a cleaning treatment. In addition, by the cleaning treatment, the ruthenium-containing residues generated on the surface of the object to be processed by the etching treatment can also be removed.

The cleaning process can be performed by contacting the cleaning liquid with the object to be treated. The contact method is not particularly limited, and examples include a method of immersing the object to be treated in the cleaning liquid placed in a tank, a method of spraying the cleaning liquid on the surface of the object to be treated, a method of flowing the cleaning liquid on the surface of the object to be treated, or any combination of these methods.

Examples of cleaning 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 and hydrogen peroxide (APM), a mixture of hydrochloric acid and hydrogen peroxide (HPM), carbon dioxide water, ozone water, hydrogen water, citric acid aqueous solution, sulfuric acid, ammonia water, isopropyl alcohol, hypochlorous acid aqueous solution, ultrapure water, nitric acid, oxalic acid aqueous solution, acetic acid (including acetic acid aqueous solution), etc. By using the cleaning liquids as described above for cleaning treatment, ruthenium-containing residues generated on the surface of the object to be treated by etching treatment can be effectively removed.

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

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

According to the above-described processing method of the present embodiment, the processing object is etched using the etching solution of the first embodiment, which contains orthoperiodic acid as an oxidant and is adjusted to a pH of 8 or more and 10 or less by ammonia. The etching solution has a low risk of ruthenium tetroxide generation and has a practical etching rate for ruthenium, so ruthenium etching can be safely performed. Therefore, the processing method of the present embodiment can be appropriately used in the micro-processing of a ruthenium-containing layer formed on a substrate or the cleaning of a ruthenium substrate, etc.

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

The manufacturing method of this embodiment can be carried out in the same manner as the method exemplified in the "Dig-in Etching Process" in the aforementioned "(Etching Solution)".

(Method for manufacturing semiconductor device) The method for manufacturing semiconductor device of this embodiment is characterized by comprising the step of etching a workpiece containing ruthenium using the etching solution of the first embodiment described above.

The step of etching the object containing ruthenium can be performed in the same manner as described in the above "(Method for treating the object)". The object containing ruthenium is preferably a substrate having a ruthenium-containing layer. As the substrate, a substrate commonly used in the manufacture of semiconductor devices can be used.

<Other steps> The manufacturing method of the semiconductor element of this embodiment may include other steps in addition to the above-mentioned etching treatment step. The other steps are not particularly limited, and examples are known steps performed during the manufacturing of semiconductor elements. Examples of such steps include, but are not limited to, various structural formation steps 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-mentioned etching treatment, chemical mechanical polishing, transformation, etc.), resist film formation step, exposure step, development step, heat treatment step, cleaning step, inspection step, etc. The other steps may be appropriately performed before or after the above etching step as required.

According to the manufacturing method of the semiconductor device of the present embodiment described above, the etching solution of the first embodiment containing orthoperiodic acid as an oxidant and adjusted to a pH of 8 or more and 10 or less by ammonia is used to perform etching treatment of the object to be processed. Since the etching solution has a low risk of ruthenium tetroxide generation and has a practical etching rate for ruthenium, it can safely perform micro-processing of the ruthenium-containing layer formed on the substrate or cleaning of the substrate. Therefore, the manufacturing method of the present embodiment can be appropriately used in the manufacture of semiconductor devices containing ruthenium wiring, etc. [Example]

The present invention is further described in detail below by way of 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. The pH at 23°C was measured using a pH meter, while ammonia was added to the orthoperiodic acid solution to adjust the pH to the values shown in Table 1. Subsequently, water was added to make the total volume of the solution 100 mL to prepare the etching solution of each example.

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

[Evaluation of etching rate] After etching by the method shown in the above "<Etching treatment of the object>", the object was taken out from the etching solution and the sheet resistance value on the substrate surface was measured. The etching rate of each example was calculated from the above sheet resistance value. The results are shown in Table 2 as "Etching rate".

[Evaluation of ruthenium tetroxide generation] Put 20 mL of each etching solution into a bottle and add 0.01 g of ruthenium powder. Immediately after adding ruthenium powder, seal the bottle inlet with wax film and leave it at room temperature for 3 days. Then, visually check the color change of the wax film and evaluate it according to the following evaluation criteria. The results are shown in Table 2 as "wax film color change". The color change of the wax film indicates the generation of ruthenium tetroxide. Evaluation criteria: ○: The wax film has not changed color ×: The wax film has changed color

As can be seen from Table 2, in Examples 1 to 5, the wax film did not change color, and no ruthenium tetroxide generation was confirmed. And the etching rate was maintained within the practical range. On the other hand, although the etching rates of Comparative Examples 1 and 2 were high, the wax film changed color, and ruthenium tetroxide generation was confirmed. In Comparative Example 3, although ruthenium tetroxide generation was not confirmed, the etching rate was low and not practical. From the above, it can be confirmed that according to the etching solution of the embodiment of the present invention, ruthenium tetroxide generation can be reduced, and ruthenium etching treatment can be performed.

<Preparation of etching solution (2)> (Examples 6 to 10, Comparative Examples 4 to 6) 2 g of orthoperiodic acid was dissolved in water. The pH at 23°C was measured using a pH meter while ammonia was added to the orthoperiodic acid solution to adjust the pH to the values shown in Table 3. Subsequently, water was added to make the total volume of the solution 2000 mL, and the solution was passed through a polytetrafluoroethylene (PTFE) filter with a pore size of 15 nm 30 times to prepare the etching solution of each example. For each etching solution, the number of particles larger than 100 nm per 1 mL of the etching solution was measured using a light scattering liquid particle detector (KS-19F, manufactured by RION). The results are recorded in Table 3 as "Number of particles (particles/mL)". Furthermore, for the etching solution described in Example 6, after measuring the number of particles without passing through the filter, the number of particles larger than 100 nm per 1 mL of the etching solution became a measured value exceeding 10,000.

<Etching treatment of the object to be processed (2)> The etching treatment of the object to be processed is performed in the same manner as <Etching treatment of the object to be processed (1)> except that the etching solution of each of Examples 6 to 10 and Comparative Examples 4 to 6 is used as the etching solution.

[Evaluation of etching rate/Evaluation of ruthenium tetroxide generation] The etching rate and ruthenium tetroxide generation were evaluated in the same manner as described above. As a result, Examples 6 to 10 and Comparative Examples 4 to 6 obtained results substantially the same as Examples 1 to 5 and Comparative Examples 1 to 3, respectively. That is, the etching rate of Examples 6 to 10 was 1 to 10 nm/min, which was maintained within the practical range. No discoloration of the wax film was observed, and no ruthenium tetroxide generation was confirmed. On the other hand, although the etching rates of Comparative Examples 4 and 5 were greater than those of the Examples, the wax film was discolored, and ruthenium tetroxide generation was confirmed. Moreover, in Comparative Example 6, although ruthenium tetroxide generation was not confirmed, the etching rate was low and impractical.

1: Wiring board 2: Depression 3: Substrate 4: Base layer 5: Insulation layer 6: Barrier metal layer 7: Wiring containing ruthenium

[FIG. 1] is a schematic diagram showing an example of a substrate having wiring containing ruthenium as a processed object during a recess etching process. [FIG. 2] is a schematic diagram showing an example of a wiring substrate after the recess etching process.

Claims (7)

An etching solution for etching ruthenium, comprising 0.5-3 mass % of orthoperiodic acid and ammonia, a pH of 8 or more and 10 or less, and no slurry or abrasive. For example, the etching solution of claim 1, wherein the number of particles larger than 100 nm contained in the etching solution is less than 20/mL. For example, the etching solution of claim 1, wherein the aforementioned etching process is not equivalent to a CMP process. The etching liquid of claim 1, wherein the etching process is a process of selectively etching the area composed of ruthenium by applying the etching liquid to a substrate whose surface layer includes an area composed of an insulating film and an area composed of ruthenium. A manufacturing method, which is a manufacturing method of an etching solution as claimed in any one of claims 1 to 4, and comprises the following steps in sequence: mixing a solution containing original periodic acid with aqueous ammonia to prepare a mixed solution, adjusting the pH of the mixed solution to a value between 8 and 10, and filtering the mixed solution with a filter. A method for treating a treated object, comprising the step of etching the treated object containing ruthenium using an etching solution as described in any one of claims 1 to 4. A method for manufacturing wiring containing ruthenium, wherein the etching treatment is for a substrate whose surface layer includes an area composed of an insulating film and an area composed of ruthenium, by applying an etching solution as described in any one of claims 1 to 4 to selectively etch the area composed of ruthenium.

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