JP2021015968A - Silicon nitride film etching solution and production method thereof - Google Patents

Abstract

To provide a silicon nitride film etching solution capable of improving a selection ratio relative to a silicone oxide film.SOLUTION: The silicon nitride film etching solution includes a phosphoric acid aqueous solution and a compound represented by the formula in the figure, where X1 to X3 are selected from C1-C20 alkoxy, a hydroxy group and halogen; and R1 to R3 are selected from hydrogen, C1-C20 alkyl group, a C6-C12 cycloalkyl, C2-C10 heteroalkyl including at least one heteroatom, C2-C10 alkenyl, C2-C10 alkynyl, C1-C10 haloalkyl, C1-C10 aminoalkyl, aryl, heteroaryl, aralkyl and halogen.SELECTED DRAWING: None

Description

The present invention relates to a silicon nitride film etching solution and a method for producing the same. More specifically, when etching a silicon nitride film, a silicon nitride film capable of improving the etching selectivity of the silicon oxide film to the silicon nitride film is possible. The present invention relates to an etching solution and this manufacturing method.

Currently, there are various methods for etching a silicon nitride film and a silicon oxide film, but a dry etching method and a wet etching method are mainly used.

The dry etching method is usually an etching method using a gas, and although it has an advantage of being more isotropic than the wet etching method, it is too inferior in productivity to the wet etching method and is an expensive method. , Wet etching method is being widely used.

In general, as a wet etching method, a method using phosphoric acid as an etching solution is well known. At this time, when only pure phosphoric acid is used for etching the silicon nitride film, not only the silicon nitride film but also the silicon oxide film is etched as the device becomes finer, so that various defects and patterns are formed. Since problems such as the occurrence of abnormalities may occur, it is necessary to form a protective film on the silicon oxide film to further reduce the etching rate of the silicon oxide film.

An object of the present invention is to provide a silicon nitride film etching solution capable of lowering the etching rate for a silicon oxide film and improving the etching selectivity for a silicon nitride film with respect to a silicon oxide film.

Another object of the present invention is to provide a silicon nitride film etching solution in which the etching rate is stably maintained in an etching process performed at a high temperature and the etching selectivity with respect to the silicon nitride film does not decrease with respect to the silicon oxide film. To do.

Another object of the present invention is to provide a method for producing the above-mentioned silicon nitride film etching solution.

In order to solve the above-mentioned technical problems, according to one aspect of the present invention, the silicon nitride film etching solution contains an aqueous phosphoric acid solution and a compound represented by the following Chemical formula 1.

[Chemical 1]

In the above 1
X _{1 to} X ₃ are independently selected from C _1- C ₂₀ alkoxy, hydroxy group and halogen, respectively, and R _{1 to} R ₃ are independently selected from hydrogen, C _1- C ₂₀ alkyl group and C _6- , respectively. C ₁₂ cycloalkyl, C _2- C ₁₀ heteroalkyl containing at least one heteroatom, C _2- C ₁₀ alkenyl, C _2- C ₁₀ alkynyl, C _1- C ₁₀ haloalkyl, C _1- C ₁₀ aminoalkyl, aryl , Heteroaryl, Alalkyl, and Halogen.

Further, according to another aspect of the present invention, (a) a step of mixing a silicon compound precursor and water to produce a mixed solution, and then adding hydroxide to the mixed solution to synthesize a silicon compound. (B) After extracting the aqueous solution of the silicon compound synthesized in the step (a) from the first organic solvent, the step of removing the first organic solvent, and (c) the result of the step (b). The step of mixing and refluxing the second organic solvent, (d) lowering the result of the step (c) to a temperature range of 30 ° C. to −40 ° C. to separate the crystallized solid compound. A method for producing a silicon nitride film etching solution is provided, which comprises (e) a step of mixing the solid compound of the step (d) with an aqueous phosphate solution to produce a mixed solution.

Among the silicon nitride film etching solutions according to the present invention, the compound represented by the above-mentioned Chemical formula 1 reduces the etching rate of the silicon oxide film with respect to the silicon oxide film by increasing the bond with the silicon oxide film under etching conditions. be able to.

At this time, the reactivity of the compound represented by the above-mentioned compound 1 used in the present application, the silicon oxide film, and the hydroxy group (-OH) is increased, so that the passivation of the excellent silicon oxide film is increased.
It can play a role as a layer).

FIG. 5 is a cross-sectional view schematically showing a step of removing a silicon nitride film using an etching solution according to an embodiment of the present invention.

The advantages and features of the present invention, and the methods for achieving them, will be clarified with reference to the examples described later. However, the present invention is not limited to the examples disclosed below, and is embodied in various different forms. However, the present embodiment is provided to complete the disclosure of the present invention and to fully inform a person having ordinary knowledge in the technical field to which the present invention belongs to the scope of the invention, and the present invention is claimed. It is only defined by the category of terms.

Hereinafter, the silicon nitride film etching solution according to the present invention and the method for producing the same will be described in detail.

<Silicon nitride film etching solution>
According to one aspect of the present invention, there is provided a silicon nitride film etching solution containing an aqueous phosphoric acid solution and the compound represented by Chemical formula 1 below.

[Chemical 1]

In the above 1
X _{1 to} X ₃ are independently selected from C _1- C ₂₀ alkoxy, hydroxy group and halogen, respectively, and R _{1 to} R ₃ are independently selected from hydrogen, C _1- C ₂₀ alkyl group and C _6- , respectively. C ₁₂ cycloalkyl, C _2- C ₁₀ heteroalkyl containing at least one heteroatom, C _2- C ₁₀ alkenyl, C _2- C ₁₀ alkynyl, C _1- C ₁₀ haloalkyl, C _1- C ₁₀ aminoalkyl, aryl , Heteroaryl, Alalkyl, and Halogen.

In the above Formula _1, two of X 1 to X ₃ are the stereochemical structure, showing the trans (trans) type.

The C _a- C _b working group in the present application means a working group having _{a to b} carbon atoms. For example, C _a- C _b alkyl means a saturated aliphatic group containing _{a to b} carbon atoms, including linear alkyl and branched chain alkyl. Straight or branched chain alkyl has 10 or fewer in the main chain of which _(e.g., linear C 1 _{-C 10,} branched of C 3 _{-C 10),} preferably 4 or less, more preferably 3 or less Has a carbon atom of.

Specifically, alkyl is methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, i-butyl, t-butyl, pent-1-yl, pent-2-yl, pent-. 3-Il, 3-methylbut-1-yl, 3-methylbut-2-yl, 2-methylbut-2-yl, 2,2,2-trimethyleth-1-yl, n-hexyl, n-heptyl, and It may be n-oxytyl.

Alkoxy in the present application means both an -O- (alkyl) group and an -O- (unsubstituted cycloalkyl) group, and comprises one or more ether groups and 1 to 10 carbon atoms. It is a straight-chain or split-chain hydrocarbon having.

Specifically, methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, tert-butoxy, sdc-butoxy, n-pentoxy, n-hexoxy, 1,2-dimethylbutoxy, cyclopropyloxy, cyclobutyloxy, cyclopentyl. It includes, but is not limited to, oxy, cyclohexyloxy and the like.

Cycloalkyl or heteroatom-containing cycloalkyl in the present application will be understood as alkyl or heteroalkyl cyclic structures, respectively, unless otherwise defined.

Non-limiting examples of cycloalkyl include cyclopentyl, cyclohexyl, 1-cyclohexenyl, 3-cyclohexenyl, and cycloheptyl.

Non-limiting examples of cycloalkyls containing heteroatoms include 1- (1,2,5,6-tetrahydropyridyl), 1-piperidinyl, 2-piperidinyl, 3-piperidinyl, 4-morpholinyl, 3-morpholinyl, Tetrahydrofuran-2-yl, tetrahydrofuran-3-yl, tetrahydrothien-2-yl, tetrahydrothien-3-yl, 1-piperazinyl, 2-piperazinyl and the like.

Further, the cycloalkyl containing a cycloalkyl or a heteroatom may have a form in which the cycloalkyl, a cycloalkyl containing a heteroatom, an aryl or a heteroaryl is bonded or covalently linked.

Aryl in the present application means an unsaturated aromatic ring containing a single ring or multiple rings (preferably 1 to 4 rings) linked or covalently linked to each other, unless otherwise defined. Non-limiting examples of aryls include phenyl, biphenyl, o-terphenyl, m-terphenyl, p-terphenyl, 1-naptyl, 2-naptyl, 1-anthryl, 2-anthryl. , 9-Anthryl, 1-Phenylthrenyl, 2-Phenylthrenyl, 3-Phenylthrenyl, 4-Phenylthrenyl, 9-Phenylthrenyl, 1-Pyrenyl, 2-Pyrenyl, and 4-Pyrenyl.

Heteroaryl in the present application means a working group in which one or more carbon atoms in the aryl defined above are substituted with non-carbon atoms such as nitrogen, oxygen or sulfur.

Alalkyl in the present application is a working group in which aryl is substituted with an alkyl carbon, and is a general term for − (CH ₂ ) _n Ar. Examples of alalkyl include benzyl (-CH ₂ C ₆ H ₅ ) or penetyl (-CH ₂ CH ₂ C ₆ H ₅ ).

Halogen in the present application means fluoro (-F), chloro (-Cl), bromo (-Br) or iodine (-I), and haloalkyl means the above-mentioned halogen-substituted alkyl. For example, halomethyl means methyl (-CH ₂ X, -CHX ₂ or -CX ₃ ) in which at least one of the hydrogens of the methyl has been replaced with a halogen.

The silicon compound usually used as an additive has the effect of protecting the silicon oxide film from the aqueous phosphoric acid solution, but on the other hand, the silicon impurities generated after etching and the silicon compound combine to form particles and contaminate the silicon substrate. There is a problem to make it.

A silane compound in which a hydrophilic acting group is bonded to a silicon atom is easily decomposed at a low temperature by a reaction with water, and a silicon-hydroxy group (-Si-OH) can be formed. In the silicon-hydroxy group, silicon atoms and oxygen atoms are alternately bonded by polymerization to form a siloxane (-Si-O-Si-) group having a random chain structure. The silane compound containing a siloxane group is, as a result, silicon-based particles in which siloxane is repeatedly polymerized, and causes a problem that storage safety is lowered due to growth and precipitation.

The silicon nitride film etching solution according to an embodiment of the present invention contains the compound represented by the following Chemical formula 1 in order to suppress the formation of particles.

[Chemical 1]

In the above 1
X _{1 to} X ₃ are independently selected from C _1- C ₂₀ alkoxy, hydroxy group and halogen, respectively, and R _{1 to} R ₃ are independently selected from hydrogen, C _1- C ₂₀ alkyl group and C _6- , respectively. C ₁₂ cycloalkyl, C _2- C ₁₀ heteroalkyl containing at least one heteroatom, C _2- C ₁₀ alkenyl, C _2- C ₁₀ alkynyl, C _1- C ₁₀ haloalkyl, C _1- C ₁₀ aminoalkyl, aryl , Heteroaryl, Alalkyl, and Halogen.

Here, the compound represented by the above-mentioned Chemical formula 1 of the present invention exhibits a cyclic structure so that the compound structure is maintained until the temperature reaches a high temperature. As a result, the generation of particles can be suppressed by reducing the phenomenon in which the silicon-hydroxy group is transformed into a siloxane (-Si-O-Si-) compound by polymerization.

Further, the silicon nitride film etching solution according to the embodiment of the present invention is for increasing the reactivity of the silicon oxide film with the hydroxy group (-OH) and increasing the etching selectivity of the silicon oxide film with respect to the silicon nitride film. Includes the compound represented by Chemical formula 1.

Specifically, the compound represented by Chemical formula 1 contained in the etching solution of the silicon nitride film is SN2 (Bimolecular) with the hydroxy group (-OH) of the silicon oxide film.
A protective layer (passivation layer) of a silicon oxide film is formed by a Nucleophilic Substation reaction. That is, the passivation of the silicon oxide film.
In order to sufficiently form the layer), the SN2 reactivity of the compound with the hydroxy group (-OH) must be increased. Specifically, the more unstable the compound structure is, the more the SN2 reactivity with the hydroxy group (-OH) can be increased. However, depending on the degree of safety of the compound structure, the compound and the hydroxy group ( Reactivity with −OH) may be determined.

The cyclic compound used as an additive in the silicon nitride film etching solution may exhibit a cis (cis) or trans (trans) type in terms of stereochemical structure.

As an example, the cis-type compound may be reacted by the following reaction formula 1 under etching conditions.

[Reaction formula 1]

As in the above reaction formula 1, the cis-type compound may react with the aqueous phosphoric acid solution under etching conditions to add a cation to the hydroxy group (-OH). Hydroxy groups by the addition of cations (-OH) may, _-OH ^{2 +} indicates, SN2 reaction of the hydroxy group (-OH) and _-OH ^{2 +} and in the molecule may be performed.

However, the cis type compound, hydroxy group _-OH ^{2 +} and nucleophile leaving groups (-OH) are not arranged axially (axial). That is, any hydroxy group cis type compound (-OH) is _-OH ^{2 +} and horizontal leaving group where is only arranged in (equatorial), cis-compounds, hydroxy group in the molecule (-OH) and _-OH ^{2 +} and the SN2 reaction is carried out difficult.

Here, the compound represented by Formula 1 of the present invention, SN2 reaction of hydroxy groups in the molecule (-OH) and -OH ₂ ⁺ and may be rows.

As an example, the compound represented by Chemical formula 1 of the present invention may be represented by the compound represented by Chemical formula 2 or Chemical formula 3 below.

[Chemical 2]

[Chemical 3]

In Chemical formulas 2 and 3, R _{1 to} R ₃ are independently selected from hydrogen, C _1- C ₂₀ alkyl group, C _6- C ₁₂ cycloalkyl, C _6- C ₃₀ aryl, and halogen, respectively. ..

Further, as an example, the trans-type compound represented by Chemical formula 2 may be reacted by the following reaction formula 2 under etching conditions.

[Reaction equation 2]

As in the above reaction formula 2, the trans-type compound of the present invention may react with an aqueous phosphoric acid solution under etching conditions to add a cation to the hydroxy group (-OH), as in the case of the cis-type compound.

However, trans-type compound of the present invention, unlike the cis type compound, hydroxy group _-OH ^{2 +} and nucleophile leaving group (-OH) is arranged in the axial direction (axial). Thereby, the trans compounds may be administered by SN2 reaction with hydroxyl groups (-OH) and _-OH ^{2 +} in the molecule, so to form an unstable Si-O-Si structure.

Here, in the trans-type compound, the SN2 reactivity with the hydroxy group (-OH) on the surface of the silicon oxide film can be increased by forming an unstable Si—O—Si structure in the molecule.

Specifically, the compound containing the unstable Si—O—Si structure and the hydroxy group (−OH) on the surface of the silicon oxide film may be reacted by the following reaction formula 3.

[Reaction equation 3]

As in the above reaction formula 3, the compound containing the unstable Si—O—Si structure has a high bond angle strain (angle).
Strine) is shown. As a result, the compound has increased SN2 reactivity with the hydroxy group (-OH) on the surface of the silicon oxide film, and can be easily bonded to the hydroxy group (-OH) on the surface of the silicon oxide film.

That is, the compound bonded to the hydroxy group (-OH) on the surface of the silicon oxide film is a passivation of the silicon oxide film.
By forming a layer) and lowering the etching rate for the silicon oxide film, it is possible to improve the etching selectivity for the silicon nitride film with respect to the silicon oxide film.

The additive containing the compound represented by Chemical formula 1 described above is preferably present in the silicon nitride film etching solution at an amount of 50 to 200,000 ppm. Here, the content of the additive is the amount of the additive dissolved in the silicon nitride film etching solution, and is shown in units of ppm. For example, the presence of an additive in a silicon nitride film etching solution at 5,000 ppm may mean that the additive dissolved in the silicon nitride film etching solution is 5,000 ppm. When the additive is present in the silicon nitride film etching solution at less than 50 ppm, the amount of the additive is not sufficient under the etching conditions, and the effect of increasing the etching selectivity with respect to the silicon nitride film is weak. possible. On the other hand, when the amount of the additive in the silicon nitride film etching solution exceeds 200,000 ppm, a problem may occur in which a large amount of silicon-based particles are generated due to an increase in the saturation concentration of the additive in the silicon nitride film etching solution. ..

Further, among the additives, the content of the trans compound represented by the above-mentioned Chemical formula 1 is preferably 50% or more. More preferably, the content of the trans compound represented by Chemical formula 1 in the additives is 90% or more. When the content represented by Chemical formula 1 is less than 50% of the additives, the reactivity with the hydroxy group (-OH) on the surface of the silicon oxide film can be reduced under etching conditions. As a result, the protective layer of the silicon oxide film cannot be sufficiently formed, and the effect of increasing the etching selectivity of the silicon oxide film on the silicon nitride film may be weak. That is, the higher the content ratio of the trans compound represented by Chemical formula 1 among the additives, the more the protective layer of the silicon oxide film is sufficiently formed, and the etching selectivity ratio of the silicon oxide film to the silicon nitride film is improved. be able to.

The silicon substrate to be etched by the silicon nitride film etching solution according to the present invention preferably contains at least a silicon oxide film (SiO _x ), and may contain both a silicon oxide film and a silicon nitride film. Further, in the case of a silicon substrate containing both a silicon oxide film and a silicon nitride film, the silicon oxide film and the silicon nitride film may be alternately laminated or may be laminated in different regions.

Here, the silicon oxide film is an SOD (Spin On Dielectric) film or HDP (High Density) depending on the application and the type of material.
Plasma) film, thermal oxide film, BPSG (Borophosphate)
Silicate Glass (Silicate Glass) Membrane, PSG (Phospho Silicate Glass) Membrane, BSG (Boro Silicate)
Glass) film, PSZ (Polysilazane) film, FSG (Fluorinated Silicate)
Glass) film, LP-TEOS (Low)
Pressure Tera Ethyl Ortho Silicate) Membrane, PETEOS (Plasma Enhanced Tera)
Ethyl Ortho Silicate) Membrane, HTO (High Temperature Oxide) Membrane, MTO (Medium)
Temperature Oxide (Temperature Oxide) Membrane, USG (Unloaded Silicate Glass) Membrane, SOG (Spin On Glass) Membrane, APL (Advanced Development)
Layer) membrane, ALD (Atomic Layer)
Deposition membrane, PE-oxide membrane (Plasma Enhanced oxide) or O _3- TEOS (O _3- Tetra Ethyl)
Ortho Silicate) and the like.

Here, the phosphoric acid aqueous solution is a component that etches the silicon nitride film and maintains the pH of the etching solution to suppress the conversion of various forms of silicon compounds existing in the etching solution into silicon-based particles. ..

In one embodiment, the phosphoric acid aqueous solution is preferably contained in an amount of 60 to 90 parts by weight with respect to 100 parts by weight of the silicon substrate etching solution.

If the content of the phosphoric acid aqueous solution is less than 60 parts by weight with respect to 100 parts by weight of the silicon substrate etching solution, the etching rate of the silicon nitride film is lowered and the silicon nitride film is not sufficiently etched, or the silicon nitride film is not sufficiently etched. There is a risk that the efficiency of the etching process will decrease.

On the other hand, when the content of the phosphoric acid aqueous solution exceeds 90 parts by weight with respect to 100 parts by weight of the silicon nitride film etching solution, the increase in the etching rate of the silicon oxide film is compared with the increase in the etching rate of the silicon nitride film. The etching selectivity for the silicon nitride film may decrease with respect to the silicon oxide film, and the etching of the silicon oxide film may cause a defect in the silicon substrate.

The silicon nitride film etching solution according to one embodiment of the present invention compensates for the etching rate of the silicon nitride film, which is lowered by using the additive, and further adds a fluorine-containing compound in order to improve the efficiency of the overall etching process. It may be included.

Fluorine-containing compounds in the present application refer to any compound in any form that dissociates fluorine ions.

In one example, the fluorine-containing compound is at least one selected from hydrogen fluoride, ammonium fluoride, ammonium bicarbonate, and ammonium hydrogen fluoride.

Further, in another embodiment, the fluorine-containing compound may be a compound in which an organic cation and a fluorine anion are ionically bonded.

For example, the fluorine-containing compound may be a compound in which an alkylammonium and a fluorine-based anion are ionically bonded. Here, the alkylammonium is an ammonium having at least one alkyl group and may have up to four alkyl groups. The definition for the alkyl group is as described above.

In yet another example, the fluorine-containing compounds are alkylpyrrolium, alkylimidazolium, alkylpyrazolium, alkyloxazolium, alkylthiazolium, alkylpyridinium, alkylpyrimidinium, alkylpyridazinium, alkylpyra. Organic cations selected from dinium, alkylpyrrolidinium, alkylphosphonium, alkylmorpholinium, and alkylpiperidinium, and fluorophosphates, fluoroalkyl-fluorophosphates, fluoroborates, and fluoroalkyl-fluoros. It may be an ionic liquid in the form of an ionic bond with a fluorine-based anion selected from the borate.

Among the silicon nitride film etching solutions, the fluorine-containing compound provided in the form of an ionic liquid has a higher boiling point and decomposition temperature than hydrogen fluoride or ammonium fluoride, which is generally used as a fluorine-containing compound, and has a high temperature. There is an advantage that there is little possibility of changing the composition of the etching solution due to decomposition during the etching step performed in 1.

According to another aspect of the present invention, there is provided a method for manufacturing a semiconductor device, which is carried out using the above-mentioned silicon nitride film etching solution.

According to this manufacturing method, a semiconductor device can be manufactured by performing a selective etching step on a silicon nitride film using the above-mentioned etching solution on a silicon substrate containing at least a silicon nitride film (SI _x N _y ). It is possible.

The silicon substrate used for manufacturing the semiconductor element may include a silicon nitride film (SI _x N _y ), or may contain both a silicon oxide film and a silicon nitride film. Further, in the case of a silicon substrate containing both a silicon oxide film and a silicon nitride film, the silicon oxide film and the silicon nitride film may be alternately laminated or may be laminated in different regions.

The method for manufacturing a semiconductor device according to the present invention may be applied to a manufacturing process for a NAND device. More specifically, among the laminated structures for forming NAND, the above-mentioned etching solution is used in a process step in which selective removal of the silicon nitride film is required without loss to the silicon oxide film. be able to.

As an example, FIG. 1 is a schematic cross-sectional view for explaining a step of removing a silicon nitride film using an etching solution according to the present invention.

Referring to FIG. 1, a mask pattern layer 30 is formed on a laminated structure 20 in which a silicon nitride film 11 and a silicon oxide film 12 are alternately laminated on a silicon substrate 10, and then an anisotropic etching step is performed. The trench 50 is formed.

Further, referring to FIG. 1, the etching solution according to the present invention is injected through the trench 50 region formed in the laminated structure 20, whereby the silicon nitride film 11 is etched and becomes the silicon oxide film 12. Only the mask pattern layer 30 remains.

That is, in the present invention, the etching of the silicon oxide film 12 in the laminated structure 20 is minimized by using an etching solution having an improved etching selectivity for the silicon nitride film with respect to the silicon oxide film, and for a sufficient time. The silicon nitride film 11 can be completely and selectively removed. After that, the semiconductor device can be manufactured through a subsequent step including a step of forming a gate electrode in the removed region of the silicon nitride film 11.

<Manufacturing method of silicon nitride film etching solution>
According to one aspect of the present invention, (a) a step of mixing a silicon compound precursor and water to produce a mixed solution, and then adding hydroxide to the mixed solution to synthesize a silicon compound, (b). A step of extracting the aqueous solution of the silicon compound synthesized in the step (a) from the first organic solvent and then removing the first organic solvent, (c) the result of the step (b) and the second step. A step of mixing an organic solvent and refluxing it, (d) lowering the result of the step (c) to a temperature range of 30 ° C. to −40 ° C. to separate a crystallized solid compound, and (E) A method for producing a silicon nitride film etching solution, which comprises the step of mixing the solid compound of the step (d) with an aqueous phosphate solution to produce a mixed solution, is provided.

First, the production method of the present invention includes (a) a step of mixing a silicon compound precursor and water to produce a mixed solution, and then adding a hydroxide to the mixed solution to synthesize a silicon compound.

The silicon compound precursor is preferably a trialkoxysilane compound. As an example, the trialkoxysilane compound is 3- (2-Aminoethylamino) propylenetimetoxysilane, Allyltimethoxysilane, and 3- (Trimethothylyl) tropyl.
It may be selected from Acrylate. The hydroxide is not particularly limited as long as it is a compound capable of providing hydroxide ions, and as an example, LiOH, NaOH, KOH, Bd (OH) ₂ , Mg (OH) ₂ , or Ca (OH) ₂ . There may be.

Further, the equivalent ratio of the silicon compound precursor: hydroxide may be 2: 1 to 1: 5. Preferably, the equivalent ratio of the silicon compound precursor: hydroxide may be 1: 1.

Next, the production method of the present invention includes (b) extracting the aqueous solution of the silicon compound synthesized in the step (a) from the first organic solvent, and then removing the first organic solvent.

More specifically, the silicon compound synthesized in step (a) can be mixed with water to produce an aqueous solution of the silicon compound and extracted from the first organic solvent. As an example, the first organic solvent is ethyl acetate (ethyl).
Acetate), dichloromethane (dichloromethane), chloroform (chloroform), hexane (Hexane), toluene (Toluene) and ether (ether) may be selected.

The aqueous solution of the silicon compound is extracted with the first organic solvent, and then the first organic solvent is removed. The method for removing the first organic solvent is not particularly limited, and as an example, the first organic solvent is a rotary evaporator (Rotary).
It can be removed using Evaporator).

Next, the production method of the present invention includes (c) the step of mixing the result of the step (b) with the second organic solvent and refluxing (reflux).

More specifically, the silicon compound extracted in step (b) and the second organic solvent can be mixed and refluxed at a high temperature. In the step (c), both the silicon compound showing cis stereochemistry and the silicon compound showing trans stereochemistry extracted by the step (b) above can be dissolved in the second organic solvent. The type of the second organic solvent is not particularly limited, and as an example, hexane, benzene, or aisopropylmethyl ether (isopropanol).
It may be methyl ether).

Next, the production method of the present invention comprises (d) lowering the result of step (c) to a temperature range of 30 ° C. to −40 ° C. to separate the crystallized solid compound.

More specifically, the solid compound crystallized by lowering the silicon compound exhibiting cis and trans stereochemistry dissolved in the non-polar solvent in step (c) to a low temperature range of 30 ° C. to -40 ° C. Can be separated. Here, even if the temperature is changed to a low temperature, the silicon compound exhibiting cis stereochemistry is still dissolved in a non-polar solvent, while the silicon compound exhibiting trans stereochemistry may crystallize and exist as a solid compound. As a result, the silicon compound exhibiting trans stereochemistry, which is a crystallized solid compound, can be separated from the silicon compound exhibiting cis stereochemistry.

Next, the production method of the present invention includes the steps of (e) mixing the solid compound of the step (d) with the phosphoric acid aqueous solution to produce a mixed solution.

The phosphoric acid aqueous solution can maintain the pH of the etching solution and suppress the change of the silicon compound existing in the etching solution into silicon-based particles. As an example, the phosphoric acid aqueous solution is preferably contained in an amount of 60 to 90 parts by weight with respect to 100 parts by weight of the mixed solution.

When the etching solution produced according to the production method of the present invention described above is used, the etching rate of the silicon oxide film by the aqueous phosphoric acid solution can be reduced to improve the etching selectivity of the silicon oxide film to the silicon nitride film.

Hereinafter, specific examples of the present invention will be presented. However, the examples described herein are merely for exemplifying or explaining the present invention, and the present invention should not be limited by this.

Example
Manufacture of etching solution
Example 1
A silicon nitride film etching solution was produced by mixing 85% by weight of phosphoric acid, 50 ppm of an additive, and the remaining amount of water. The additive contains the following cis-type compound 1 and trans-type compound 2, and the content ratio of the compound 1 and the compound 2 is 9: 1.

[Compound 1]

[Compound 2]

Example 2
A silicon nitride film etching solution was produced in the same manner as in Example 1 except that the content ratio of Compound 1 and Compound 2 in Example 1 was 7: 3.

Example 3
A silicon nitride film etching solution was produced in the same manner as in Example 1 except that the content ratio of Compound 1 and Compound 2 in Example 1 was 5: 5.

Example 4
A silicon nitride film etching solution was produced in the same manner as in Example 1 except that the content ratio of Compound 1 and Compound 2 in Example 1 was 3: 7.

Example 5
A silicon nitride film etching solution was produced in the same manner as in Example 1 except that the content ratio of Compound 1 and Compound 2 in Example 1 was 1: 9.

Comparative Example 1
A silicon nitride film etching solution was produced in the same manner as in Example 1 except that the additive contained only Compound 1 of Example 1.

Experimental Example A silicon nitride film etching solution having the compositions according to Examples 1 to 5 and Comparative Example 1 is immersed in a heated etching solution at 175 ° C. to immerse a silicon oxide film (thermal oxide layer) having a thickness of 500 Å and a silicon nitride film. Etched for 10 minutes.

Before and after etching, the thickness of the silicon oxide film and the silicon nitride film is determined by ellipsometry (Nano-View, SE).
It is measured using MG-1000; Ellipmetry), and the etching rate is a numerical value calculated by dividing the difference in thickness between the silicon oxide film and the silicon nitride film by the etching time (10 minutes) before and after etching. Is.

The etching rates measured using silicon nitride film etching solutions having different silica shapes are shown in Table 1 below.

[Table 1]

As shown in Table 1 above, the silicon nitride film etching solution of Examples 1 to 5 can reduce the etching rate for the silicon oxide film as compared with the silicon nitride film etching solution of Comparative Example 1, whereby the etching rate for the silicon oxide film can be lowered. It can be confirmed that the etching selectivity for the silicon nitride film is improved with respect to the silicon oxide film.

In particular, as shown in Table 1 above, the higher the content ratio of the trans-type compound among the additives, the lower the etching rate with respect to the silicon oxide film, whereby the silicon nitride film with respect to the silicon oxide film can be further reduced. It can be confirmed that the etching selectivity with respect to is further improved.

In the above, one embodiment of the present invention has been described, but any person having ordinary knowledge in the technical field can add components within the scope of the idea of the present invention described in the claims. The present invention can be modified and changed in various ways by modification, deletion, addition, etc., and it can be said that this is also included in the scope of rights of the present invention.

10 Silicon substrate 11 Silicon nitride film 12 Silicon oxide film 20 Laminated structure 30 Mask pattern layer 50 Trench

Claims (10)

Phosphoric acid aqueous solution;
Including the compound represented by Chemical formula 1 below;
Silicon nitride film etching solution:
[Chemical 1]

In the above 1
X _{1 to} X ₃ are independently selected from C _1- C ₂₀ alkoxy, hydroxy groups and halogens, respectively.
R _{1 to} R ₃ are independent hydrogen, C _1- C ₂₀ alkyl group, C _6- C ₁₂ cycloalkyl, C _2- C ₁₀ heteroalkyl containing at least one hetero atom, C _2- C ₁₀ alkenyl. , C _2- C ₁₀ alkynyl, C _1- C ₁₀ haloalkyl, C _1- C ₁₀ aminoalkyl, aryl, heteroaryl, alalkyl, and halogen. The silicon nitride film etching solution according to claim 1, wherein the compound represented by Chemical formula 1 is a compound represented by Chemical formula 2 or Chemical formula 3 below.
[Chemical 2]

[Chemical 3]

_R 1 to R ₃ in the chemical formula 2 and chemical formula 3 are each independently _hydrogen, C 1 _{-C 20} alkyl _group, C 6 _{-C 12 cycloalkyl,} is selected from C 6 _{-C 30} aryl and halogen. Among the silicon nitride film etching solutions, the additive containing the compound represented by the above-mentioned Chemical formula 1 is characterized by being contained in an amount of 50 to 200,000 ppm.
The silicon nitride film etching solution according to claim 1. The silicon nitride film etching solution further contains at least one fluorine-containing compound selected from hydrogen fluoride, ammonium fluoride, ammonium bicarbonate, and ammonium hydrogen fluoride.
The silicon nitride film etching solution according to claim 1. The silicon nitride film etching solution further contains a fluorine-containing compound having an ion-bonded form of an organic cation and a fluorine-based anion.
The silicon nitride film etching solution according to claim 1. (A) A step of mixing a silicon compound precursor and water to produce a mixed solution, and then adding a hydroxide to the mixed solution to synthesize a silicon compound;
(B) A step of extracting the aqueous solution of the silicon compound synthesized in the step (a) from the first organic solvent and then removing the first organic solvent;
(C) The step of mixing the result of the step (b) with the second organic solvent and refluxing (reflux);
(D) The step of lowering the result of step (c) to a temperature range of 30 ° C. to −40 ° C. to separate the crystallized solid compound;
(E) The step of mixing the solid compound of the step (d) with the aqueous phosphoric acid solution to produce a mixed solution;
A method for producing a silicon nitride film etching solution. The silicon compound precursor in step (a) is characterized by being a trialkoxysilane compound.
The method for producing a silicon nitride film etching solution according to claim 6. The equivalent ratio of the silicon compound precursor: hydroxide of the step (a) is 2: 1 to 1: 5.
The method for producing a silicon nitride film etching solution according to claim 6. The first organic solvent in step (b) is ethyl acetate (ethtl).
Acetate), dichloromethane (dichloromethane), chloroform (chloroform), hexane (Hexane), toluene (Toluene), and ether (ether).
The method for producing a silicon nitride film etching solution according to claim 6. The solid compound in step (d) is a silicon compound exhibiting trans stereochemistry.
The method for producing a silicon nitride film etching solution according to claim 6.

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