TWI869458B - Etching liquid, and method for manufacturing semiconductor device - Google Patents

Abstract

An etching liquid is used for selectively etching compounds represented by the general formula Si _1-x Ge _x (however, x exceeds 0 and does not reach 1) for Si, Ge and their oxides, and comprises a fluoride and an oxidant, wherein the fluoride comprises hexafluorosilicic acid, and the etching rate A measured under the following conditions is above 10Å/min. (A measurement conditions) A substrate having a Si _0.75 Ge _0.25 layer on the surface is immersed in the etching liquid at 25°C, and the etching rate is measured.

Description

Etching liquid, and method for manufacturing semiconductor device

The present invention relates to an etching solution and a method for manufacturing a semiconductor device. This application claims priority based on Special Application No. 2019-183804 filed in Japan on October 4, 2019 and Special Application No. 2020-155651 filed in Japan on September 16, 2020, the contents of which are incorporated herein.

In the past, the scaling of components within integrated circuits has enabled the densification of functional units on semiconductor chips. For example, the reduction in transistor size has made it possible to fit more memory components on a chip, thereby producing products with increased capacity.

In the manufacture of field effect transistors (FETs) for integrated circuit devices, Ge is used as a semiconductor crystal material other than silicon. Ge has higher charge carrier (hole) mobility, band gap offset, different lattice constants, and the ability to form an alloy with silicon to form a semiconductor binary alloy of SiGe. Depending on the situation, it has more favorable characteristics than silicon.

Various etching solutions with high selectivity for Ge materials (especially compounds represented by the general formula Si1 _{- xGex} , but x exceeds 0 and is less than 1. Hereinafter, they are sometimes referred to as "SiGe compounds") have been proposed. For example, Patent Document 1 describes an etching composition containing at least one diol compound, at least one fluoride species, and at least one oxide species. [Prior Art Document] [Patent Document]

[Patent Document 1] Japanese Patent Publication No. 2018-519674

[Problems to be solved by the invention]

However, when using the conventional etching solution described in Patent Document 1, not only SiGe compounds are etched, but also Si or _SiO2 , etc., and it is difficult to selectively etch SiGe compounds relative to Si or _SiO2 , etc. The present invention is completed in view of the above situation, and its subject is to provide an etching solution that can selectively etch compounds represented by the general formula Si1 _{- xGex} for Si, Ge and their oxides, and a method for manufacturing a semiconductor using the etching solution. [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, which is used for selectively etching compounds represented by the general formula Si _1-x Ge _x (however, x exceeds 0 and does not reach 1) for Si, Ge and their oxides, and comprises a fluoride and an oxidant, wherein the fluoride comprises hexafluorosilicic acid, and the etching rate A measured under the following conditions is above 10Å/min. (A measurement conditions) A substrate having a Si _0.75 Ge _0.25 layer on its surface is immersed in the etching solution at 25°C, and the etching rate is measured.

The second aspect of the present invention is a method for manufacturing a semiconductor device, which includes the step of using the aforementioned etching solution to etch a workpiece containing a compound represented by the general formula Si _1-x Ge _x . [Effect of the invention]

According to the etching solution of the present invention, compounds represented by the general formula Si _1-x Ge _x can be selectively etched on Si, Ge and their oxides. In addition, according to the semiconductor manufacturing method of the present invention, semiconductors can be manufactured by selectively etching compounds represented by the general formula Si _1-x Ge _x on Si, Ge and their oxides.

(Etching fluid)

The first embodiment of the present invention comprises a fluoride and an oxidant, wherein the fluoride comprises silicic acid hexafluoride. The etchant of this embodiment is used to selectively etch Si, Ge and their oxides to form a compound represented by the general formula Si1 _{-xGex (} where x exceeds 0 and is less than 1) (hereinafter sometimes referred to as "SiGe compound").

The etching rate A of the etching solution of this embodiment measured under the following conditions is 10Å/min or more, preferably 15Å/min or more, more preferably 20Å/min or more, even more preferably 50Å/min or more, and particularly preferably 80Å/min or more. (A measurement conditions) A substrate having a Si _0.75 Ge _0.25 layer on its surface is immersed in the etching solution at 25°C to measure the etching rate.

The etching solution of this embodiment has good selectivity for SiGe compounds by making the etching rate A above 10Å/min. In addition, if the etching rate A of the etching solution of this embodiment is above the lower limit of the above preferred range, the selectivity for SiGe compounds is further improved.

When the etching rate measured under the following conditions is set as the etching rate B, the etching liquid of the present embodiment preferably has an A/B ratio of 10 or more, more preferably an A/B ratio of 15 or more, still more preferably an A/B ratio of 20 or more, still more preferably an A/B ratio of 30 or more, still more preferably an A/B ratio of 70 or more, and particularly preferably an A/B ratio of 90 or more. (B measurement conditions) A cover substrate having a _SiO2 layer on its surface is immersed in the etching liquid at 25°C, and the etching rate is measured.

The etching solution of this embodiment can further improve the etching selectivity of SiGe compounds relative to _SiO2 by setting A/B to above the lower limit of the above-mentioned preferred range.

<Fluoride> The etching solution of this embodiment contains hexafluorosilicic acid as a fluoride. The fluoride other than hexafluorosilicic acid is not particularly limited, and examples thereof include hexafluorotitanium acid, hexafluorosilicic acid, hexafluorozirconic acid, tetrafluoroboric acid, tetrabutylammonium trifluoromethanesulfonate, tetrabutylammonium tetrafluoroborate, and other tetraalkylammonium tetrafluoroborates (NR ₁ R ₂ R ₃ R ₄ BF ₄ ), tetraalkylammonium hexafluorophosphates (NR 1 R 2 R 3 R ₄ PF ₆ ), tetraalkylammonium fluorides (NR ₁ R _{2 R} 3 R 4 F) such as tetramethylammonium fluoride (NR ₁ R ₂ R ₃ R ₄ F) (anhydrous or hydrate thereof), ammonium difluoride, ammonium fluoride (wherein R ₁ , R ₂ , R ₃ , and R ₄ are the same or different from each other and are selected from hydrogen, a linear or branched C ₁ -C ₆ alkyl (e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl), C ₁ -C ₆ alkoxy (e.g., hydroxyethyl, hydroxypropyl) or substituted or unsubstituted aryl (e.g., benzyl) etc. The etching solution of this embodiment preferably contains only hexafluorosilicic acid as the fluoride.

In the etching solution of this embodiment, the fluoride may be used alone or in combination of two or more. The fluoride content in the etching solution of this embodiment is not particularly limited, but for example, it is 0.02~5 mass%, preferably 0.025~3.00 mass%, more preferably 0.03~2.50 mass%, and more preferably 0.04~2.00 mass% relative to the total mass of the etching solution. If the fluoride content is within the above range, it is easier to increase the etching rate for SiGe compounds.

The fluorine ion concentration in the etching solution of the present embodiment is not particularly limited, but is exemplified as 0.005 to 2.50 mol/L, preferably 0.007 to 1.50 mol/L, more preferably 0.008 to 1.25 mol/L, and even more preferably 0.010 to 1.00 mol/L. If the fluorine ion concentration is within the above range, it is easier to increase the etching rate for SiGe compounds.

<Oxidant> Examples of the oxidant include hydrogen peroxide, FeCl ₃ , FeF ₃ , Fe(NO ₃ ) ₃ , Sr(NO ₃ ) ₂ , CoF ₃ , MnF ₃ , potassium hydrogen persulfate (Oxone) (2KHSO ₅・KHSO ₄・K ₂ SO ₄ ), hydroiodic acid, vanadium (V) oxide, vanadium (IV, V) oxide, ammonium vanadate, ammonium persulfate, ammonium chlorite, ammonium chlorate, ammonium iodate, ammonium nitrate, ammonium perborate, ammonium perchlorate, ammonium periodate, ammonium persulfate, ammonium hypochlorite, ammonium hypobromite, ammonium tungstate, sodium persulfate, sodium hypochlorite, sodium perborate, sodium hypobromite, sodium iodate, Potassium manganate, potassium persulfate, nitric acid, potassium persulfate, potassium hypochlorite, tetramethylammonium chlorite, tetramethylammonium iodate, tetramethylammonium perborate, tetramethylammonium perchlorate, tetramethylammonium periodate, tetramethylammonium persulfate, tetrabutylammonium peroxysulfate, peroxysulfuric acid, iron nitrate, urea peroxide, peracetic acid, orthoperiodic acid (H ₅ IO ₆ ), metaperiodic acid (HIO ₄ ), methyl-1,4-benzoquinone (MBQ), 1,4-benzoquinone (BQ), 1,2-benzoquinone, 2,6-dichloro-1,4-benzoquinone (DCBQ), toluenequinone, 2,6-dimethyl-1,4-benzoquinone (DMBQ), chloranil, alloxan, N-methylmorpholine N-oxide, trimethylamine N-oxide, etc. Among them, the oxidizing agent is preferably nitric acid or orthoperiodic acid, and more preferably nitric acid.

In the etching solution of this embodiment, the oxidant may be used alone or in combination of two or more. The content of the oxidant in the etching solution of this embodiment may be, for example, 5 to 50 mass%, preferably 5.5 to 45 mass%, more preferably 6 to 40 mass%, and even more preferably 7 to 35 mass%, relative to the total mass of the etching solution. If the content of the oxidant is within the above range, the SiGe compound is easily oxidized, and it is easier to increase the etching rate of the SiGe compound.

<Other components> The etching solution of this embodiment may contain other components in addition to the above components within the scope that does not impair the effect of the present invention. Examples of other components include solvents, pH adjusters, passivating agents, surfactants, etc.

・Solvent The etching solution of this embodiment is preferably prepared by mixing hydrofluoric acid, an oxidizing agent, and other optional components in a solvent. The solvent is not particularly limited, and examples thereof include water, polar organic solvents, phosphoric acid, and/or its derivatives.

・Water When the etching solution of the present embodiment contains water as a solvent, the water may also 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 purified such as distilled water, deionized water, and ultrapure water, and it is more preferable to use ultrapure water generally used in semiconductor manufacturing. When the etching solution of the present embodiment contains water, the content of water is, for example, 3 to 50 mass %, preferably 3.5 to 45 mass %, more preferably 4 to 40 mass %, and more preferably 4.5 to 40 mass % relative to the total mass of the etching solution.

・Polar organic solvent The etching solution of this embodiment may contain a polar organic solvent within the range that does not impair the effect of the present invention. Examples of polar organic solvents include organic carboxylic acid solvents (e.g., acetic acid, formic acid, etc.), alcohol solvents (e.g., methanol, ethanol, ethylene glycol, propylene glycol, glycerol, 1,3-propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, diethylene glycol, dipropylene glycol, furfuryl alcohol, and 2-methyl-2,4-pentanediol, etc.), dimethyl sulfoxide, and ether solvents (e.g., ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, propylene glycol dimethyl ether), etc. Among them, the polar organic solvent is preferably an organic carboxylic acid solvent, and more preferably acetic acid.

In the etching solution of the present embodiment, the polar organic solvent may be used alone or in combination of two or more. When the etching solution of the present embodiment contains the polar organic solvent, the content of the polar organic solvent is, for example, 20 to 90% by mass, preferably 25 to 85% by mass, more preferably 30 to 80% by mass, and even more preferably 35 to 75% by mass relative to the total mass of the etching solution.

・Phosphoric acid and its derivatives The etching solution of this embodiment may contain phosphoric acid and/or its derivatives as a solvent within the range that does not impair the effect of the present invention. Examples of phosphoric acid and/or its derivatives are compounds represented by the following general formula (1).

[In the formula, each R is independently a hydrogen atom or an alkyl group having 1 to 20 carbon atoms].

In the above formula (1), examples of the alkyl group with 1 to 20 carbon atoms in R include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, isotridecyl, tetradecyl, pentadecyl, hexadecyl, isohexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, and isomers of the above alkyl groups. Among them, R is preferably a hydrogen atom or an alkyl group with 1 to 10 carbon atoms, and more preferably a hydrogen atom.

In the etching solution of the present embodiment, phosphoric acid and/or its derivatives as solvents may be used alone or in combination of two or more. When the etching solution of the present embodiment contains phosphoric acid and/or its derivatives as solvents, the content of phosphoric acid and/or its derivatives is, for example, 1 to 50 mass %, preferably 2 to 45 mass %, more preferably 3 to 40 mass %, and even more preferably 5 to 35 mass % relative to the total mass of the etching solution.

In the etching solution of the present embodiment, one solvent may be used alone or two or more solvents may be used in combination. In the etching solution of the present embodiment, when two or more solvents are used in combination, a combination of water and a polar organic solvent or a combination of water and phosphoric acid and/or its derivatives is preferred, a combination of water and an organic carboxylic acid solvent or a combination of water and phosphoric acid and/or its derivatives is more preferred, and a combination of water and acetic acid or a combination of water and phosphoric acid is more preferred.

When the etching solution of the present embodiment contains a combination of water and a polar organic solvent as a solvent, the mass ratio of water to the polar organic solvent is preferably 1/15 to 1/1, more preferably 1/12 to 9/10, and even more preferably 1/10 to 8/10.

When the etching solution of the present embodiment contains a combination of water and phosphoric acid and/or its derivatives as a solvent, the mass ratio of water to polar organic solvent is preferably 1/1 to 10/1, more preferably 1.1/1 to 9/1, and even more preferably 1.2/1 to 8/1.

When the etching solution of this embodiment includes a solvent, the content of the solvent is, for example, 23-95% by mass, preferably 23.5-94.5% by mass, more preferably 24-94% by mass, and more preferably 24.5-93.5% by mass relative to the total mass of the etching solution.

・pH adjuster The etching solution of this embodiment may also contain a pH adjuster in order to further increase the etching rate of SiGe compounds. The pH adjuster is preferably at least one selected from the group consisting of acids and their salts. Specific examples include methanesulfonic acid, trifluoromethanesulfonic acid, oxalic acid dihydrate, citric acid, tartaric acid, picolinic acid, succinic acid, acetic acid, lactic acid, sulfosuccinic acid, benzoic acid, propionic acid, formic acid, pyruvic acid, maleic acid, malonic acid, fumaric acid, apple acid, ascorbic acid, mandelic acid, heptanoic acid, butyric acid, valeric acid, glutaric acid, phthalic acid, hypophosphorous acid, salicylic acid, 5-sulfosalicylic acid, hydrochloric acid, ethanesulfonic acid, butanesulfonic acid, p-toluenesulfonic acid, dichloroacetic acid, difluoroacetic acid, monochloroacetic acid, monofluoroacetic acid, trifluoroacetic acid, trifluoroacetic acid, hydrobromic acid (62 % by weight, sulfuric acid, ammonium acetate, sodium acetate, potassium acetate, tetramethylammonium acetate and other tetraalkylammonium acetates, phosphonium acetate, ammonium butyrate, ammonium trifluoroacetate, ammonium carbonate, ammonium chloride, ammonium sulfate, phosphoric acid, diammonium hydrogen phosphate, diammonium dihydrogen phosphate, bis(tetramethylammonium) hydrogen phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, di-tetraalkylammonium hydrogen phosphate, di-tetraalkylammonium dihydrogen phosphate, diphosphonium hydrogen phosphate, diphosphonium phosphate, ammonium phosphonates, tetraalkylammonium phosphonates, sodium phosphonates, potassium phosphonates, phosphonium phosphonates, hydroxyethylidene diphosphonic acid and their salts, etc. Among these, methanesulfonic acid or oxalic acid is preferred as the acid pH adjuster.

In addition, the etching solution of the present embodiment may also contain an alkaline compound as a pH adjuster. As such alkaline compounds, organic alkaline compounds and inorganic alkaline compounds may be used. As organic alkaline compounds, preferred examples include quaternary ammonium salts represented by organic quaternary ammonium hydroxide, alkylamines such as trimethylamine and triethylamine, and salts of their derivatives. Moreover, examples of inorganic alkaline compounds include inorganic compounds containing alkaline metals or alkaline earth metals and their salts. Examples include lithium hydroxide, sodium hydroxide, potassium hydroxide, arsenic hydroxide, and cesium hydroxide.

In the etching solution of the present embodiment, the pH adjuster may be used alone or in combination of two or more. When the etching solution of the present embodiment includes a pH adjuster, the pH adjuster content is, for example, 0.01 to 10 mass%, preferably 0.02 to 4.5 mass%, more preferably 0.03 to 4 mass%, and more preferably 0.05 to 3 mass%, relative to the total mass of the etching solution. If the pH adjuster content is within the above range, it is easier to increase the etching rate of the SiGe compound.

・Passivating Agent The etching solution of this embodiment may also contain a passivating agent for germanium. Examples of the passivating agent include ascorbic acid, L(+)-ascorbic acid, isoascorbic acid, ascorbic acid derivatives, boric acid, ammonium diborate, borate salts (e.g., ammonium pentaborate, sodium tetraborate, and ammonium diborate), alanine, arginine, asparagine, aspartic acid, cysteine, glutamine, glutamine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, valeric acid, sodium bromide, potassium bromide, ammonium bromide, magnesium bromide, calcium bromide, a compound having the formula NR ¹ R ² R ³ R ⁴ Br (wherein R ^R1 , ^R2 , ^R3 and ^R4 may be the same as or different from each other and are selected from the group consisting of hydrogen and branched or linear _C1 - _C6 alkyl (e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl), ammonium bromide, and the like.

In the etching solution of this embodiment, the passivating agent may be used alone or in combination of two or more. When the etching solution of this embodiment contains the passivating agent, for example, the amount thereof is preferably 0.01 to 5% by mass, and more preferably 0.1 to 1% by mass, relative to the total mass of the etching solution.

・Surfactant The etching solution of this embodiment may contain a surfactant for the purpose of adjusting the wettability of the etching solution to the object to be processed. As the surfactant, a nonionic surfactant, an anionic surfactant, a cationic surfactant, or an amphoteric surfactant may be used, and these surfactants may 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, alkylsulfonic acid, fatty acid salts, etc. Examples of "salts" include ammonium salts, sodium salts, potassium salts, tetramethylammonium salts, etc.

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.

<Object to be processed> The etching liquid of this embodiment is used to etch SiGe compounds, and the object to be processed that contains SiGe compounds is the object of etching. The object to be processed is not particularly limited as long as it contains SiGe compounds, but an example is a substrate having a SiGe compound layer (containing SiGe compound 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 magnetic disks. The aforementioned substrate is preferably a substrate used to manufacture semiconductor devices. In addition to the SiGe compound 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 need to be a SiGe compound layer. For example, the middle layer of the multi-layer structure may also be a SiGe compound 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 aforementioned SiGe-containing compound layer is preferably a layer containing a SiGe compound, and more preferably a SiGe compound film. The thickness of the SiGe-containing compound layer on the substrate is not particularly limited and can be appropriately selected according to the purpose. The thickness of the SiGe-containing compound layer is, for example, in the range of 1 to 500 nm or 1 to 300 nm.

The aforementioned object to be processed may include, in addition to the SiGe compound, at least one selected from the group consisting of Si, Ge and oxides thereof, and preferably includes SiO ₂ .

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

According to the etching solution of the present embodiment described above, since it contains hexafluorosilicic acid as a fluoride, it can selectively etch compounds represented by the general formula Si1 _{-xGex (} SiGe compounds) for Si, Ge and their oxides. The reason has not yet been determined, but it is speculated as follows. If the etching solution of the present embodiment comes into contact with a processed object containing a SiGe compound, the SiGe compound is oxidized by the oxidant. The oxide of the SiGe compound is etched by the fluoride ions ( ^F- ) in the hexafluorosilicic acid. On the other hand, the silicon (Si) in the hexafluorosilicic acid plays a role in protecting Si or _SiO2 in the processed object from being etched by the fluoride ions ( ^F- ). Therefore, the etching solution of this embodiment is estimated to have improved etching selectivity of SiGe compound with respect to Si, Ge and their oxides, compared with fluorides such as hydrofluoric acid (HF) or ammonium fluoride (NH ₄ F) used in conventional etching solutions.

(Method for manufacturing semiconductor device) The method for manufacturing semiconductor device of the second aspect of the present invention is characterized by comprising the step of using the etching solution of the first aspect to etch a workpiece containing SiGe compound.

An example of a processed object containing a SiGe compound is the same as that described in "<Processed Object>" in the above "(Etching Solution)", and a substrate having a SiGe compound layer is preferably exemplified. The method for forming the SiGe compound layer on the substrate is not particularly limited, and a known method can be used. Examples of the method 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 SiGe compound layer used when forming the SiGe compound layer on the substrate are also not particularly limited, and can be appropriately selected according to the film formation method. The aforementioned object to be processed may include, in addition to the SiGe compound, at least one selected from the group consisting of Si, Ge and oxides thereof, and preferably includes SiO ₂ .

<Step of etching the object to be processed> This step is a step of etching the object to be processed containing a SiGe compound using the etching solution of the first embodiment, and includes an operation of bringing the etching solution into contact with the object to be processed. 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 to be processed in a specific direction, spray the etching solution of the first embodiment in the space thereof, and bring the etching solution into contact with the object to be processed. If necessary, a rotary coater can also 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 with the etching liquid.

The purpose of etching treatment is not particularly limited. It can be fine processing of the processed surface containing SiGe compounds of the processed body (for example, the SiGe compound layer on the substrate), or it can be the removal of SiGe compound attachments attached to the processed body (for example, the substrate with the SiGe compound layer), or it can be the cleaning of the processed surface containing SiGe compounds of the processed body (for example, the SiGe compound layer on the substrate). The purpose of etching treatment is the fine processing of the processed surface containing SiGe compounds of the processed body. Usually, the parts that should not be etched are covered by etching masks to make the processed body contact with the etching liquid. The purpose of etching treatment is to remove SiGe compound-containing attachments attached to the treated body. By bringing the etching liquid of the first state into contact with the treated body, the SiGe compound-containing attachments are dissolved, and the SiGe compound attachments can be removed from the treated body. The purpose of etching treatment is to clean the treated surface of the treated body containing SiGe compounds. By bringing the etching liquid of the first state into contact with the treated body, the aforementioned treated surface is quickly dissolved, and impurities such as particles attached to the surface of the treated body are removed from the surface of the treated body in a short time.

The temperature for etching is not particularly limited, as long as the SiGe compound can be dissolved in the aforementioned etching solution. The etching temperature is 15-60°C, for example. 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 by considering the suppression of the composition change of the etching solution or the workability, safety, cost, etc.

The etching time can be appropriately selected according to the purpose of the etching, the amount of SiGe compound to be removed by etching (e.g., the thickness of the SiGe compound layer, the amount of SiGe compound attachments, etc.), and the etching conditions.

<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 method for manufacturing a semiconductor device of the embodiment described above, the etching solution of the first embodiment containing hexafluorosilicic acid as a fluoride is used to perform etching treatment on the object to be treated. The etching solution can selectively etch Si, Ge and their oxides to treat compounds represented by the general formula Si _1-x Ge _x (SiGe compound). Therefore, according to the method for manufacturing a semiconductor device of the embodiment, Si, Ge and their oxides are substantially unaffected, and a semiconductor device in which the SiGe compound is selectively etched can be obtained. [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 9, Comparative Examples 1 to 2) Mix the components shown in Table 1 to prepare the etching solution of each example.

In Table 1, each abbreviation has the following meanings. The values in [ ] are the mixing amounts (mass %). H ₂ SiF ₆ : hexafluorosilicic acid HF: hydrofluoric acid NH ₄ F: ammonium fluoride HNO ₃ : nitric acid AcOH: acetic acid

<Etching treatment of the object to be treated (1)> A substrate having a Si _0.75 Ge _0.25 layer on its surface was immersed in an etching solution at 25°C, and the etching rate was measured. The results are shown in Table 2.

<Etching treatment of the object to be treated (2)> The SOI substrate was immersed in the etching solution at 25°C and the etching rate was measured. The results are shown in Table 2.

<Etching treatment of the object to be treated (3)> A cover substrate having a _SiO2 layer on its surface was immersed in an etching solution at 25°C, and the etching rate was measured. The results are shown in Table 2.

From the results shown in Table 2, it is confirmed that the etching solutions of Examples 1 to 9 have a higher SiGe etching selectivity than the etching solutions of Comparative Examples 1 to 2.

<Preparation of etching solution (2)> (Examples 10-13, Comparative Examples 3-4) Mix the components shown in Table 3 to prepare the etching solution of each example.

In Table 3, each abbreviation has the following meanings. The values in [ ] are the mixing amounts (mass %). H ₂ SiF ₆ : hexafluorosilicic acid HF: hydrofluoric acid HNO ₃ : nitric acid H ₃ PO ₄ : phosphoric acid

<Etching treatment of the object to be treated (1)> A substrate having a Si _0.75 Ge _0.25 layer on its surface was immersed in an etching solution at 25°C, and the etching rate was measured. The results are shown in Table 4.

<Etching treatment of the object to be treated (2)> The SOI substrate was immersed in the etching solution at 25°C and the etching rate was measured. The results are shown in Table 4.

<Etching treatment of the object to be treated (3)> A cover substrate having a _SiO2 layer on its surface was immersed in an etching solution at 25°C, and the etching rate was measured. The results are shown in Table 4.

From the results shown in Table 4, it is confirmed that the etching solutions of Examples 10 to 13 have a higher SiGe etching selectivity than the etching solutions of Comparative Examples 3 to 4.

The above describes the preferred embodiments of the present invention, but the present invention is not limited to these embodiments. Additions, omissions, substitutions and other changes can be made within the scope of the present invention. The present invention is not limited by the above description, but only by the scope of the attached patent application.

Claims (5)

An etchant is used for selectively etching Si, Ge and their oxides. The etchant is a compound represented by the general formula Si _1-x Ge _x (however, x exceeds 0 and does not reach 1), and comprises a fluoride and an oxidant. The fluoride comprises hexafluorosilicic acid, the content of the fluoride is 0.02-5% by mass relative to the total mass of the etchant, the content of the oxidant is 5-50% by mass relative to the total mass of the etchant, and further comprises an organic carboxylic acid in an amount of 20-90% by mass relative to the total mass of the etchant, or phosphoric acid and/or its derivatives in an amount of 1-50% by mass relative to the total mass of the etchant. The etching rate A measured under the following conditions is above 10Å/min. (A measurement conditions) The surface of the etchant having Si _0.75 Ge The _0.25 layer of the cover substrate was immersed in the etching solution at 25°C and the etching rate was measured. Such as the etching solution of claim 1, wherein the aforementioned oxidizing agent is nitric acid. In the etching solution of claim 1 or 2, when the etching rate measured under the following conditions is set as etching rate B, A/B is greater than 10, (B measurement condition) a cover substrate having a _SiO2 layer on its surface is immersed in the etching solution at 25°C, and the etching rate is measured. A method for manufacturing a semiconductor device comprises the step of using an etching solution as described in any one of claims 1 to 3 to etch a workpiece containing a compound represented by the general formula Si _1-x Ge _x . The method for manufacturing a semiconductor device as claimed in claim 4, wherein the object to be processed further comprises SiO ₂ .