JP2021103765A - Etching solution and method for manufacturing semiconductor element - Google Patents

Abstract

To provide an etching solution which is able to selectively perform an etching process on a compound represented by a General Formula Si1-xGex with respect to Si, Ge, and oxides thereof, and with which etching stops do not easily occur, and a method for manufacturing a semiconductor using the etching solution.SOLUTION: An etching solution for selectively performing an etching process on a compound represented by a General Formula Si1-xGex (where x is more than 0 and less than 1) with respect to Si, Ge, and oxides thereof includes hydrofluoric acid, nitric acid, and water. A content ratio of the hydrofluoric acid in the entire etching solution, is 0.002% by mass or more and 1.0% by mass or less, a content ratio of the nitric acid in the entire etching solution is 10% by mass or more, and a content ratio of the water in the entire etching solution is 40% by mass or less.SELECTED DRAWING: None

Description

The present invention relates to an etching solution and a method for manufacturing a semiconductor element.

Conventionally, scaling of configurations in integrated circuits has made it possible to increase the density of functional units on semiconductor chips. For example, reducing the transistor size makes it possible to incorporate more memory elements onto the chip, leading to the manufacture of products with increased capacity.

Ge is used as a semiconductor crystal material other than silicon in the manufacture of field effect transistors (FETs) for integrated circuit devices. Ge has high charge carrier (hole) mobility, bandgap offset, different lattice constants, and in some cases advantages over silicon, such as the ability to alloy with silicon to form a semiconductor binary alloy of SiGe. It has some features.

An etching solution having high selectivity for a Ge material (particularly _{, a compound represented by the general formula Si 1-x} Ge _x . However, x is more than 0 and less than 1. In the following, it may be simply referred to as “SiGe compound”). Various proposals have been made.
For example, it is known that an etching solution containing hydrofluoric acid (DHF) and nitric acid has a high etching ratio of a SiGe compound with respect to _{Si, SiO 2, and the like (see, for example, Patent Document 1).}

On the other hand, if the etching solution containing hydrofluoric acid (DHF) and nitric acid is continuously etched for a long time when only SiGe in the laminated structure composed of Si / SiGe / Si is selectively etched, for example, SiGe There was a problem that the etching of the layer stopped in the middle (so-called etching stop occurs). For this reason, there is a problem that when the SiGe is removed, the etching of the Si layer proceeds unintentionally, a stable shape cannot be obtained, the transistor characteristics vary, and the yield is further deteriorated.

In order to solve the above problem, Patent Document 1 proposes the following method.
(Method 1)
While rotating the substrate provided with the SiGe layer, the fluorine nitric acid solution is sprayed for a short time of about several tens of seconds to etch the SiGe layer. Then, while rotating the substrate, the spraying of the fluorine nitric acid solution is temporarily stopped. Then, while rotating the substrate, the fluorinated nitric acid solution consisting of the new liquid is sprayed again.
(Method 2)
A substrate having a SiGe layer is immersed in a fluorine solution stored in an etching tank, and the SiGe layer is wet-etched for a short time of about 1 minute. Then, it is taken out from the etching tank and immersed in a water washing tank to be washed with water. Then, the substrate is immersed in the fluorine nitric acid solution stored in the etching tank again, and wet etching is performed for a short time of about 1 minute. In this way, the etching process and the water washing process are repeated a plurality of times.

Japanese Unexamined Patent Publication No. 2008-160073

However, the method described in Patent Document 1 has a problem that it is not practical in terms of production efficiency and manufacturing cost because the number of steps in the manufacturing process increases.
The present invention has been made in view of the above circumstances, Si, Ge, and the general formula Si _1-x Ge represented by _x compounds selectively etched possible for these oxides, and An object of the present invention is to provide an etching solution that does not easily cause an etching stop, and a method for manufacturing a semiconductor using the etching solution.

In order to solve the above problems, the present invention has adopted the following configuration.

A first aspect of the present invention, Si, Ge, and the compound represented by the formula _{Si 1-x} Ge _x with respect to these oxides (here, x is less than 0 ultra 1.) Selectively It is an etching solution for etching, which contains silicon fluoride acid, nitric acid, and water, and the content ratio of the hydrofluoric acid in the entire etching solution is 0.002% by mass or more and 1.0 mass by mass. % Or less, the content ratio of the nitric acid in the entire etching solution is 10% by mass or more, and the content ratio of the water in the entire etching solution is 40% by mass or less.

A second aspect of the present invention, using the etching solution, the object to be processed comprising a general formula Si _1-x Ge represented by _x compound comprising the step of etching is a method for manufacturing a semiconductor device.

According to the etching solution of the present invention, Si, Ge, and the compound represented by the general formula Si _1-x Ge _x with respect to these oxides, it can be selectively etched while suppressing etching stop.
Further, according to the semiconductor manufacturing method of the present invention, for producing Si, Ge, and semiconductors compound represented by the general formula Si _1-x Ge _x is selectively etched with respect to these oxides be able to.

(Etching liquid)
The etching solution according to the first aspect of the present invention contains hydrofluoric acid, nitric acid, and water. Etching solution according to the present embodiment, Si, Ge, and the compound represented by the formula _{Si 1-x} Ge _x with respect to these oxides (here, x is less than 0 ultra 1.) (Hereinafter, simply (Sometimes referred to as "SiGe compound")) is used for selectively etching.

<Hydrofluoric acid>
The etching solution according to this embodiment contains hydrofluoric acid (DHF).
The content ratio of hydrofluoric acid in the entire etching solution is 0.002% by mass or more and 1.0% by mass or less, preferably 0.005% by mass or more and 0.9% by mass or less, and more preferably 0.001. It is mass% or more and 0.8 mass% or less, more preferably 0.01 mass% or more and 0.7 mass% or less, and further preferably 0.02 mass% or more and 0.6 mass% or less.
When the content of hydrofluoric acid is within the above range, the etching rate for the SiGe compound is improved.

<Nitric acid>
The etching solution according to this embodiment _{contains nitric acid (HNO 3} ).
The content ratio of nitric acid in the entire etching solution is 10% by mass or more, preferably 10% by mass or more and 55% by mass or less, more preferably 11% by mass or more and 55% by mass or less, and further preferably 12% by mass or more. It is 54% by mass or less. More preferably, it is 15% by mass or more and 54% by mass or less.
When the content of nitric acid is within the above range, the SiGe compound is easily oxidized, and the etching rate for the SiGe compound is improved.

<Water>
The etching solution of this embodiment contains water.
Water may contain trace components that are inevitably mixed. The water used for the etching solution of the present embodiment is preferably distilled water, ion-exchanged water, and water that has been subjected to purification treatment such as ultrapure water, and ultrapure water generally used for semiconductor production is used. Is more preferable.
The content ratio of water in the entire etching solution is 40% by mass or less, preferably 5% by mass or more and 40% by mass or less, more preferably 6% by mass or more and 38% by mass or less, and further preferably 7% by mass or more. It is 36% by mass or less, more preferably 8% by mass or more and 35% by mass or less.
When the water content is within the above range, the etching rate of SiGe can be controlled.

<Other ingredients>
The etching solution of the present embodiment may contain other components in addition to the above components as long as the effects of the present invention are not impaired. Examples of other components include solvents, phosphoric acid and / or derivatives thereof, pH adjusters, passivation agents, surfactants and the like.

-Solvent The etching solution of the present embodiment can be prepared by mixing hydrofluoric acid, nitric acid, water and other optional components with a solvent.
The solvent is not particularly limited, and examples thereof include polar organic solvents.

-Polar Organic Solvent The etching solution of the present embodiment may contain a polar organic solvent as long as the effects of the present invention are not impaired. Examples of the polar organic solvent include organic carboxylic acid solvents (for example, acetic acid, formic acid, etc.) and alcohol solvents (for example, methanol, ethanol, ethylene glycol, propylene glycol, glycerin, 1,3-propanediol, 1,3-butane). Diol, 1,4-butanediol, diethylene glycol, dipropylene glycol, furfuryl alcohol, and 2-methyl-2,4-pentanediol, etc.), dimethylsulfoxide, ether solvents (eg, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tri) (Ethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, propylene glycol dimethyl ether) and the like can be mentioned.
Among them, as the polar organic solvent, an organic carboxylic acid solvent is preferable, and acetic acid is more preferable.

In the etching solution of the present embodiment, one type of polar organic solvent may be used alone, or two or more types may be used in combination.
When the etching solution of the present embodiment contains a polar organic solvent, the content of the polar organic solvent is, for example, 10 to 90% by mass, preferably 11 to 85% by mass, based on the total mass of the etching solution. -80% by mass is more preferable.

-Phosphoric acid and / or its derivative The etching solution of the present embodiment may contain phosphoric acid and / or its derivative as a solvent as long as the effect of the present invention is not impaired. Examples of phosphoric acid and / or its derivative include compounds represented by the following general formula (1).

［式中、各Ｒはそれぞれ独立に、水素原子又は炭素数１〜２０のアルキル基である。］

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

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

In the etching solution of the present embodiment, one type of phosphoric acid and / or a derivative thereof may be used alone, or two or more types may be used in combination.
When the etching solution of the present embodiment contains phosphoric acid and / or a derivative thereof, the content of phosphoric acid and / or a derivative thereof is exemplified by, for example, 1 to 40% by mass with respect to the total mass of the etching solution. It is preferably ~ 38% by mass, more preferably 3 to 37% by mass, and even more preferably 5 to 35% by mass.

-PH adjuster The etching solution of the present embodiment may contain a pH adjuster in order to further improve the etching rate for the SiGe compound.
As the pH adjuster, at least one selected from the group consisting of acids and salts thereof is preferable. Specifically, 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, pyruvate, Maleic acid, malonic acid, fumaric acid, malic acid, ascorbic acid, mandelic acid, heptanic acid, butyric acid, valeric acid, glutaric acid, phthalic acid, hypophosphite, salicylic acid, 5-sulfosalicylic acid, hydrochloric acid, ethanesulfonic acid, Butane sulfonic acid, p-toluene sulfonic acid, dichloroacetic acid, difluoroacetic acid, monochloroacetic acid, monofluoroacetic acid, trichloroacetic acid, trifluoroacetic acid, hydrobromic acid (62% by weight), sulfuric acid, ammonium acetate, sodium acetate, potassium acetate , Tetramethylammonium acetate and other tetraalkylammonium acetate, phosphonium acetate, ammonium butyrate, ammonium trifluoroacetate, ammonium carbonate, ammonium chloride, ammonium sulfate, phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, hydrogen phosphate Bis (tetramethylammonium), disodium hydrogen phosphate, sodium dihydrogen phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, ditetraalkylammonium hydrogen phosphate, ditetraalkylammonium dihydrogen phosphate, phosphate Examples thereof include diphosphonium hydrogen hydrogen, phosphonium dihydrogen phosphate, ammonium phosphonate, tetraalkylammonium phosphonate, sodium phosphonate, potassium phosphonate, phosphonium phosphonate, and salts thereof.
Of these, ammonium acetate or ammonium sulfate is preferable.

Further, the etching solution of the present embodiment may contain a basic compound as a pH adjuster. Organic alkaline compounds and inorganic alkaline compounds can be used as such basic compounds, and examples of the organic alkaline compounds include quaternary ammonium salts such as organic quaternary ammonium hydroxide, trimethylamine and triethylamine. Alkaline amines and salts of derivatives thereof are preferred examples.
Inorganic alkaline compounds include inorganic compounds containing alkali metals or alkaline earth metals and salts thereof. For example, lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide and the like can be mentioned.

In the etching solution of the present embodiment, one type of pH adjuster may be used alone, or two or more types may be used in combination.
When the etching solution of the present embodiment contains a pH adjusting agent, the content of the pH adjusting agent is, for example, 0.01 to 10% by mass with respect to the total mass of the etching solution, and is 0.02 to 4.5. The mass% is preferable, 0.03 to 4% by mass is more preferable, and 0.05 to 3% by mass is further preferable. When the content of the pH adjuster is within the above range, the etching rate for the SiGe compound is likely to be improved.

-Passivation agent The etching solution of the present embodiment may contain a passivation agent for germanium.
Passivation agents include aspartic acid, L (+)-ascorbic acid, isoleucine acid, aspartic acid derivatives, boric acid, ammonium diborate, borate (eg ammonium pentaborate, sodium tetraborate and diborate). Ammonium acid), alanine, arginine, aspartic acid, aspartic acid, cysteine, glutamic acid, glutamine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, valine, sodium bromide, potassium bromide , Rubidium bromide, magnesium bromide, calcium bromide, formula NR ¹ R ² R ³ R ⁴ Br (in the formula, R ¹ , R ² , R ³ and R ⁴ are the same or different from each other. and can also, hydrogen, and branched or straight chain C ₁ -C ₆ alkyl (e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl) ammonium bromide or the like having a.) it is selected from the group consisting of the Can be mentioned.

In the etching solution of the present embodiment, one type of passivation agent may be used alone, or two or more types may be used in combination.
When the etching solution of the present embodiment contains a passivation agent, for example, 0.01 to 5% by mass is preferable, and 0.1 to 1% by mass is more preferable with respect to the total mass of the etching solution.

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

Examples of nonionic surfactants include polyalkylene oxide alkylphenyl ether-based surfactants, polyalkylene oxide alkyl ether-based surfactants, block polymer-based surfactants composed of polyethylene oxide and polypropylene oxide, and polyoxyalkylene distyreneation. Examples thereof include phenyl ether-based surfactants, polyalkylene tribenzyl phenyl ether-based surfactants, and acetylene polyalkylene oxide-based surfactants.

Examples of anionic surfactants include alkyl sulfonic acid, alkylbenzene sulfonic acid, alkylnaphthalene sulfonic acid, alkyldiphenyl ether sulfonic acid, fatty acid amide sulfonic acid, polyoxyethylene alkyl ether carboxylic acid, polyoxyethylene alkyl ether acetic acid, and polyoxyethylene. Examples thereof include alkyl ether propionic acid, alkyl phosphonic acid, and fatty acid salts. Examples of the "salt" include ammonium salt, sodium salt, potassium salt, tetramethylammonium salt and the like.

Examples of the cationic surfactant include a quaternary ammonium salt-based surfactant, an alkylpyridium-based surfactant, and the like.

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

These surfactants are generally commercially available. One type of surfactant may be used alone. Two or more types may be used in combination.

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

The SiGe compound-containing layer is preferably a layer containing a SiGe compound, and more preferably a SiGe compound film. The thickness of the SiGe compound-containing layer on the substrate is not particularly limited and can be appropriately selected depending on the intended purpose. Examples of the thickness of the SiGe compound-containing layer include a range of 1 to 200 nm and 1 to 20 nm.

In addition to the SiGe compound, the object to be treated may contain at least one selected from the group consisting of Si, Ge, and oxides thereof, and preferably contains _{SiO 2.}

The etching solution of the present embodiment may be used for microfabrication of the SiGe compound-containing layer on the substrate, may be used for removing SiGe compound-containing deposits adhering to the substrate, and SiGe may be used on the surface. It may be used to remove impurities such as particles from the object to be treated having the compound-containing layer.

According to the etching solution of the present embodiment described above, since it contains a specific amount of hydrofluoric acid, nitric acid, and water, the general formula Si _1-x Ge _{x is applied to Si, Ge, and their oxides.} It is possible to selectively etch the compound represented by (SiGe compound) and suppress the etching stop of the SiGe compound. The reason is not clear, but it is presumed as follows. When the etching solution of the present embodiment is brought into contact with the object to be treated containing the SiGe compound, the SiGe compound is oxidized by nitric acid. The oxide of the SiGe compound is etched by ^{fluoride ions (F −) in hydrofluoric acid.} Specifically, SiGe is removed by the electrochemical reaction of the following formula (1).
Si (Ge) + HNO ₃ + 6HF → H ₂ Si (Ge) F ₆ + HNO ₂ + H ₂ O + H ₂ ... (1)
As shown in the above formula (1), when a SiGe compound is etched for a long time using an etching solution containing hydrofluoric acid and nitric acid, the oxidation rate of Ge by nitric acid and nitrite is faster than that of Si, so etching is in progress. There is a possibility that so-called etching stop occurs in which the Ge concentration on the outermost surface of the SiGe layer decreases and the etching of the SiGe layer stops in the middle.
However, since the etching solution of the present embodiment contains hydrofluoric acid, nitric acid, and water within a specific range, the oxidation rates of Si and Ge are equal to each other, and the etching stop of the SiGe compound is suppressed. , SiGe compound) is presumed to be selectively etched.

(Manufacturing method of semiconductor element)
The method for manufacturing a semiconductor device according to the second aspect of the present invention is characterized by including a step of etching an object to be processed containing a SiGe compound by using the etching solution according to the first aspect.

Examples of the object to be treated containing the SiGe compound include the same as those described in "<Object to be processed>" in the above "(etching liquid)", and a substrate having a SiGe compound-containing layer is preferably exemplified. The method for forming the SiGe compound-containing layer on the substrate is not particularly limited, and a known method can be used. Examples of such a method include a sputtering method, a chemical vapor deposition (CVD) method, an epitaxy growth method, and an atomic layer deposition (ALD) method. The raw material of the SiGe compound-containing layer used when forming the SiGe compound-containing layer on the substrate is not particularly limited, and can be appropriately selected depending on the film forming method.
In addition to the SiGe compound, the object to be treated may contain at least one selected from the group consisting of Si, Ge, and oxides thereof, and preferably contains _{SiO 2.}

<Step of etching the object to be processed>
This step is a step of etching the object to be processed containing the SiGe compound by using the etching solution according to the first aspect, and includes an operation of bringing the etching solution into contact with the object to be processed. The etching treatment method is not particularly limited, and a known etching method can be used. Examples of such a method include, but are not limited to, a spray method, a dipping method, a liquid filling method, and the like.
In the spray method, for example, the object to be processed is conveyed or rotated in a predetermined direction, and the etching solution according to the first aspect is sprayed into the space to bring the etching solution into contact with the object to be processed. If necessary, the etching solution may be sprayed while rotating the substrate using a spin coater.
In the dipping method, the object to be processed is immersed in the etching solution according to the first aspect, and the etching solution is brought into contact with the object to be processed.
In the liquid filling method, the etching solution according to the first aspect is filled on the object to be treated, and the object to be treated and the etching solution are brought into contact with each other.
These etching treatment methods can be appropriately selected depending on the structure, material, and the like of the object to be treated. In the case of the spray method or the liquid filling method, the amount of the etching solution supplied to the object to be processed may be such that the surface to be processed in the object to be processed is sufficiently wet with the etching solution.

The purpose of the etching treatment is not particularly limited, and the surface to be treated containing the SiGe compound of the object to be treated (for example, the SiGe compound-containing layer on the substrate) may be finely processed, and the object to be treated (for example, containing the SiGe compound) may be finely processed. It may be the removal of the SiGe compound-containing deposits adhering to the substrate having a layer), or the cleaning of the surface to be treated containing the SiGe compound of the object to be treated (for example, the SiGe compound-containing layer on the substrate). ..

The temperature at which the etching treatment is performed is not particularly limited, and may be any temperature as long as the SiGe compound dissolves in the etching solution. Examples of the temperature of the etching process include 15 to 60 ° C. In all of the spray method, the dipping method, and the liquid filling method, increasing the temperature of the etching solution increases the etching rate, but the change in the composition of the etching solution can be kept small, and workability and safety can be improved. The processing temperature can be appropriately selected in consideration of cost and the like.

The time for performing the etching treatment is appropriately determined according to the purpose of the etching treatment, the amount of SiGe compound removed by etching (for example, the thickness of the SiGe compound-containing layer, the amount of SiGe compound deposits, etc.), and the etching treatment conditions. , Just select.

<Other processes>
The method for manufacturing a semiconductor device of the present embodiment may include other steps in addition to the etching treatment step. The other steps are not particularly limited, and examples thereof include known steps performed when manufacturing a semiconductor device. Such a step includes, for example, a step of forming each structure (layer) such as channel formation, High-K / metal gate formation, metal wiring, gate structure, source structure, drain structure, insulating layer, ferromagnetic layer, and non-magnetic layer. Formation, etching other than the above etching process, chemical mechanical polishing, modification, etc.), resist film forming step, exposure step, developing step, heat treatment step, cleaning step, inspection step, and the like, but are not limited thereto. These other steps can be appropriately performed before or after the etching treatment step, if necessary.

According to the method for manufacturing a semiconductor device of the present embodiment described above, an etching treatment of an object to be processed is performed using the etching solution according to the first aspect, which contains a specific amount of hydrofluoric acid, nitric acid, and water. I do. The etchant, Si, Ge, and the compound represented by the formula _{Si 1-x} Ge x and (SiGe compound) selectively etched with respect to these oxides, and the etch stop SiGe compound It can be suppressed. Therefore, according to the method for manufacturing a semiconductor device of the present embodiment, a semiconductor device in which a SiGe compound is selectively etched can be obtained without substantially affecting Si, Ge, and their oxides. .. Further, according to the method for manufacturing a semiconductor device of the present embodiment, since the etching stop of the SiGe compound is suppressed, the SiGe compound can be selectively etched for a longer time (for example, 3 minutes or more) than before. Therefore, the method for manufacturing a semiconductor element of the present embodiment does not require a complicated etching process, not only improves in-plane etching uniformity, but also shortens the processing time, resulting in low cost and high practicality.

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

<Preparation of etching solution (1)>
(Examples 1 to 6, Comparative Examples 1 to 6)
Each component shown in Table 1 was mixed to prepare an etching solution of each example.

In Table 1, each abbreviation has the following meaning.
DHF: Hydrofluoric acid HNO ₃ : Nitric acid AcOH: Acetic acid DIW: Water

<Etching treatment of the object to be treated (1)>
A SiGe film was epitaxially grown on a silicon substrate to obtain a processed body (1) on which the SiGe film was formed. A test piece was cut out from the obtained object to be treated (1), and the film thickness of the SiGe film was measured by fluorescent X-ray analysis. As a result, the film thickness was 50 nm.
The etching solution of each example was placed in a beaker, and the test piece was immersed in the etching solution of each example for 5 minutes at room temperature (23 ° C.) to perform an etching treatment. After the etching treatment, the test piece was dried by a nitrogen blow, and the film thickness of the SiGe film was measured by fluorescent X-ray analysis. The etching rate (nm / min) with respect to SiGe was calculated from the film thickness of the SiGe film before and after the etching treatment. The results are shown in Table 2.

<Etching treatment of the object to be treated (2)>
A silicon oxide film was formed on a silicon substrate by thermal oxidation to obtain a processed body (2). A test piece was cut out from the obtained object to be treated (2), and the film thickness of the silicon oxide film was measured by spectroscopic ellipsometry. As a result, the film thickness was 100 nm.
The etching solution of each example was placed in a beaker, and the test piece was immersed in the etching solution of each example for 5 minutes at room temperature (23 ° C.) to perform an etching treatment. After the etching treatment, the test piece was dried by a nitrogen blow, and the film thickness of the silicon oxide film was measured by spectroscopic ellipsometry. The etching rate (nm / min) with respect to Si was calculated from the film thickness of the silicon oxide film before and after the etching treatment. The results are shown in Table 2.

<Etching treatment of the object to be treated (3)>
A test piece was cut out from the SOI (100) substrate to obtain an object to be treated (3). When the film thickness of the Si film of the obtained object to be treated (3) was measured by spectroscopic ellipsometry, the film thickness was 100 nm.
The etching solution of each example was placed in a beaker, and the test piece was immersed in the etching solution of each example for 5 minutes at room temperature (23 ° C.) to perform an etching treatment. After the etching treatment, the test piece was dried by a nitrogen blow, and the film thickness of the Si film was measured by spectroscopic ellipsometry. The etching rate (nm / min) with respect to Si was calculated from the film thickness of the Si film before and after the etching treatment. The results are shown in Table 2.

<Evaluation of etching selectivity (1)>
Based on the results of the etching rate obtained in the above-mentioned "etching treatment of the object to be processed (1)", "etching treatment of the object to be processed (2)" and "etching treatment of the object to be processed (3)". The etching selectivity of the processed body (1) / the object to be processed (2) and the etching selectivity of the object to be processed (1) / the object to be processed (3) were calculated. The results are shown in Table 2.

<Etching stop evaluation (1)>
In the above "etching treatment (1) of the object to be processed", the etching rate (nm / min) with respect to SiGe when the etching treatment time is changed to the following according to the obtained SiGe etching rate (nm / min). It was calculated and evaluated according to the following criteria.
-When the SiGe etching rate is 10 nm / min or less The etching treatment time was compared at 1 minute, 3 minutes, and 5 minutes, and evaluated according to the following evaluation criteria.
⊚: The rate of change of the etching rate (nm / min) for SiGe after the etching treatment for 1 minute from the etching rate for SiGe after the etching treatment for 5 minutes is within 20%.
Δ: The rate of change of the etching rate (nm / min) for SiGe after the etching treatment for 1 minute from the etching rate for SiGe after the etching treatment for 5 minutes is more than 20% ×: For SiGe after the etching treatment for 5 minutes. Etching rate is 0.6 nm / min or less ・ SiGe etching rate is more than 10 nm / min and 20 nm / min or less The etching treatment times were compared at 30 seconds, 90 seconds, and 150 seconds, and evaluated according to the following evaluation criteria.
⊚: The rate of change of the etching rate (nm / min) for SiGe after the etching treatment for 30 seconds from the etching rate for SiGe after the etching treatment for 150 seconds is within 20%.
Δ: The rate of change from the etching rate (nm / min) for SiGe after etching treatment for 30 seconds from the etching rate for SiGe after etching treatment for 150 seconds is more than 20% ×: For SiGe after etching treatment for 5 minutes. Etching rate is 0.6 nm / min or less ・ SiGe etching rate is more than 20 nm / min and 50 nm / min or less The etching treatment times were compared at 20 seconds, 40 seconds, and 60 seconds, and evaluated according to the following evaluation criteria.
⊚: The rate of change of the etching rate (nm / min) for SiGe after the etching treatment for 20 seconds from the etching rate for SiGe after the etching treatment for 60 seconds is within 20%.
Δ: The rate of change from the etching rate (nm / min) for SiGe after etching treatment for 20 seconds from the etching rate for SiGe after etching treatment for 60 seconds is more than 20% ×: For SiGe after etching treatment for 5 minutes. Etching rate is 0.6 nm / min or less

From the results shown in Table 2, it was confirmed that the etching solutions of Examples 1 to 6 had a higher SiGe etching selectivity and that the etching stop of SiGe was suppressed as compared with the etching solutions of Comparative Examples 1 to 6. Was done.

(Examples 7 to 10, Comparative Example 7)
Each component shown in Table 3 was mixed to prepare an etching solution of each example.

In Table 3, each abbreviation has the following meaning.
DHF: Hydrofluoric acid HNO ₃ : Nitric acid AcOH: Acetic acid H ₃ PO ₄ : Phosphoric acid DIW: Water

<Etching treatment of the object to be treated (4)>
The etching rate (nm / min) for SiGe was calculated in the same manner as in the above "<Etching treatment (1) of the object to be treated>" except that the etching solutions of Comparative Examples 7 and 7 to 10 were used. The results are shown in Table 4.

<Etching treatment of the object to be treated (5)>
The etching rate (nm / min) for Si was calculated in the same manner as in the above-mentioned "<Etching treatment (2) of the object to be treated>" except that the etching solutions of Comparative Examples 7 and 7 to 10 were used. The results are shown in Table 4.

<Etching treatment of the object to be treated (6)>
The etching rate (nm / min) for Si was calculated in the same manner as in the above "<Etching treatment (3) of the object to be treated>" except that the etching solutions of Comparative Examples 7 and 7 to 10 were used. The results are shown in Table 4.
<Evaluation of etching selectivity (2)>
Based on the results of the etching rate obtained in the above-mentioned "etching treatment of the object to be processed (4)", "etching treatment of the object to be processed (5)" and "etching treatment of the object to be processed (6)", the object to be processed The etching selectivity of the processed body (4) / the object to be processed (5) and the etching selectivity of the object to be processed (4) / the object to be processed (6) were calculated. The results are shown in Table 4.

<Etching stop evaluation (2)>
In the above-mentioned "etching treatment of the object to be treated (4)", the etching treatment time is set to the same as the above-mentioned "<Etching stop evaluation (1)>" according to the obtained SiGe etching rate (nm / min). The etching rate (nm / min) for SiGe at the time of change was calculated and evaluated according to the same criteria as the above "<Etching stop evaluation (1)>". The results are shown in Table 4.

From the results shown in Table 4, it was confirmed that the etching solutions of Examples 7 to 10 had a higher SiGe etching selectivity and that the etching stop of SiGe was suppressed as compared with the etching solutions of Comparative Example 7. ..

Claims (7)

An etching solution for etching a compound represented by the general formula Si _1-x Ge _x (where x is more than 0 and less than 1).
Contains hydrofluoric acid, nitric acid, and water,
The content ratio of the hydrofluoric acid in the entire etching solution is 0.002% by mass or more and 1.0% by mass or less.
The content ratio of the nitric acid in the entire etching solution is 10% by mass or more, and the content is 10% by mass or more.
An etching solution in which the content of water in the entire etching solution is 40% by mass or less. The etching solution according to claim 1, further comprising a polar organic solvent. The etching solution according to claim 2, wherein the polar organic solvent is acetic acid. The etching solution according to any one of claims 1 to 3, wherein the content ratio of the nitric acid in the entire etching solution is 55% by mass or less. The etching solution according to any one of claims 1 to 4, wherein the content ratio of the water in the entire etching solution is 5% by mass or more. The etching solution according to any one of claims 1 to 5, further comprising phosphoric acid and / or a derivative thereof. Using an etching solution according to any one of claims 1 to 6, the object to be processed comprising a general formula Si _1-x Ge represented by _x compound comprising the step of etching, a method of manufacturing a semiconductor device ..