KR102749433B1 - Etching solution for silicon nitride layer and method for preparing the same - Google Patents

Abstract

The present invention relates to a silicon nitride film etching solution and a method for producing the same, and more specifically, to a silicon nitride film etching solution and a method for producing the same, wherein a compound having a trans structure represented by chemical formula 1 in the silicon nitride film etching solution can lower the etching rate of a silicon nitride film compared to a silicon oxide film by increasing bonding with a silicon oxide film under etching conditions.

Description

{ETCHING SOLUTION FOR SILICON NITRIDE LAYER AND METHOD FOR PREPARING THE SAME}

The present invention relates to a silicon nitride film etching solution and a method for producing the same, and more specifically, to a silicon nitride film etching solution capable of improving the etching selectivity for a silicon nitride film compared to a silicon oxide film when etching the silicon nitride film, and a method for producing the same.

Currently, there are several methods for etching silicon nitride and silicon oxide films, but dry etching and wet etching are the most commonly used methods.

Dry etching is an etching method that typically uses gas and has the advantage of superior isotropy compared to wet etching. However, since it is less productive and more expensive than wet etching, wet etching is increasingly being used.

In general, a wet etching method using phosphoric acid as an etching solution is well known. At this time, if only pure phosphoric acid is used to etch the silicon nitride film, problems such as various defects and pattern abnormalities may occur as the silicon nitride film as well as the silicon oxide film are etched as the device becomes miniaturized. Therefore, it is necessary to form a protective film on the silicon oxide film to further reduce the etching speed of the silicon oxide film.

The present invention aims 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 compared to a silicon oxide film.

In addition, the present invention aims to provide a silicon nitride film etching solution in which an etching rate is stably maintained in an etching process performed at high temperature and the etching selectivity for a silicon nitride film compared to a silicon oxide film is not reduced.

In addition, the present invention aims to provide a method for manufacturing the above-described silicon nitride film etching solution.

In order to solve the above-described technical problem, according to one aspect of the present invention, a silicon nitride film etching solution includes a phosphoric acid aqueous solution and a compound represented by the following chemical formula 1.

[Chemical Formula 1]

In the above chemical formula 1,

X ₁ to X ₃ are each independently selected from C ₁ -C ₂₀ alkoxy, a hydroxy group and a halogen, and R ₁ to R ₃ are each independently selected from hydrogen, a C ₁ -C ₂₀ alkyl group, a C6-C12 cycloalkyl, a C2-C10 heteroalkyl comprising at least one heteroatom, a C ₂ -C ₁₀ alkenyl, a C ₂ -C ₁₀ alkynyl, a C ₁ -C ₁₀ haloalkyl, a C ₁ -C ₁₀ aminoalkyl, aryl, heteroaryl, aralkyl and halogen.

In addition, according to another aspect of the present invention, a method for producing a silicon nitride film etching solution is provided, including the steps of: (a) mixing a silicon compound precursor and water to prepare a mixed solution, and then adding a hydroxide to the mixed solution to synthesize a silicon compound, (b) extracting an aqueous solution of the silicon compound synthesized in step (a) with a first organic solvent and then removing the first organic solvent, (c) mixing the resultant of step (b) with a second organic solvent and refluxing, (d) lowering the temperature of the resultant of step (c) to a temperature range of 30° C. to -40° C. to separate a crystallized solid compound, and (e) mixing the solid compound of step (d) with an aqueous phosphoric acid solution to prepare a mixed solution.

Among the silicon nitride film etching solutions according to the present invention, the compound represented by the chemical formula 1 can lower the etching rate for a silicon nitride film compared to a silicon oxide film by increasing bonding with the silicon oxide film under etching conditions.

At this time, the reactivity between the compound represented by the chemical formula 1 used in the present invention and the silicon oxide film and the hydroxyl group (-OH) increases, so that it can play a role as an excellent passivation layer of the silicon oxide film.

Figure 1 is a cross-sectional view schematically illustrating a silicon nitride film removal process using an etching solution according to one embodiment of the present invention.

The advantages and features of the present invention, and the method for achieving them, will become clear with reference to the embodiments described below. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and these embodiments are provided only to make the disclosure of the present invention complete and to fully inform a person having ordinary skill in the art to which the present invention belongs of the scope of the invention, and the present invention is defined only by the scope of the claims.

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

<silicon Nitride film Etching Solution>

According to one aspect of the present invention, a silicon nitride film etching solution is provided, which comprises a phosphoric acid aqueous solution and a compound represented by the following chemical formula 1.

[Chemical Formula 1]

In the above chemical formula 1,

X ₁ to X ₃ are each independently selected from C ₁ -C ₂₀ alkoxy, a hydroxy group and a halogen, and R ₁ to R ₃ are each independently selected from hydrogen, a C ₁ -C ₂₀ alkyl group, a C6-C12 cycloalkyl, a C2-C10 heteroalkyl comprising at least one heteroatom, a C ₂ -C ₁₀ alkenyl, a C ₂ -C ₁₀ alkynyl, a C ₁ -C ₁₀ haloalkyl, a C ₁ -C ₁₀ aminoalkyl, aryl, heteroaryl, aralkyl and halogen.

Additionally, in the chemical formula 1, two of X ₁ to X ₃ represent a trans form in terms of stereochemical structure.

As used herein, the C _a -C _b functional group means a functional group having a to b carbon atoms. For example, C _a -C _b alkyl means a saturated aliphatic group including straight-chain alkyl and branched alkyl having a to b carbon atoms. Straight-chain or branched alkyl has 10 or fewer carbon atoms in its main chain (e.g., straight chain of C ₁ -C ₁₀ , branched chain of C ₃ -C ₁₀ ), preferably 4 or fewer, more preferably 3 or fewer.

Specifically, alkyl can be methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, i-butyl, t-butyl, pent-1-yl, pent-2-yl, pent-3-yl, 3-methylbut-1-yl, 3-methylbut-2-yl, 2-methylbut-2-yl, 2,2,2-trimethyleth-1-yl, n-hexyl, n-heptyl and n-octyl.

As used herein, alkoxy refers to both an -O-(alkyl) group and an -O-(unsubstituted cycloalkyl) group, and is a straight-chain or branched hydrocarbon having one or more ether groups and 1 to 10 carbon atoms.

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

In the present invention, unless otherwise defined, cycloalkyl or cycloalkyl containing a hetero atom (heterocycloalkyl) may be understood as a cyclic structure of alkyl or heteroalkyl, respectively.

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

Non-limiting examples of cycloalkyls containing hetero atoms 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, and 2-piperazinyl.

Additionally, a cycloalkyl or a cycloalkyl containing a hetero atom may have a form in which a cycloalkyl, a cycloalkyl containing a hetero atom, an aryl or a heteroaryl is bonded or covalently linked thereto.

As used herein, unless otherwise defined, aryl means an unsaturated aromatic ring comprising a single ring or multiple rings (preferably 1 to 4 rings) joined to each other by fusion or covalent bonds. Non-limiting examples of aryl include phenyl, biphenyl, o-terphenyl, m-terphenyl, p-terphenyl, 1-naphthyl, 2-naphthyl, 1-anthryl, 2-anthryl, 9-anthryl, 1-phenanthrenyl, 2-phenanthrenyl, 3-phenanthrenyl, 4-phenanthrenyl, 9-phenanthrenyl, 1-pyrenyl, 2-pyrenyl, and 4-pyrenyl.

As used herein, heteroaryl refers to a functional group in which one or more carbon atoms in the aryl defined above are replaced with a non-carbon atom such as nitrogen, oxygen or sulfur.

In this application, aralkyl is a functional group in which aryl is substituted on the carbon of alkyl, and is a general term for -(CH ₂ ) _n Ar. Examples of aralkyl include benzyl (-CH ₂ C ₆ H ₅ ) or phenethyl (-CH ₂ CH ₂ C ₆ H ₅ ).

As used herein, halogen means fluoro (-F), chloro (-Cl), bromo (-Br), or iodo (-I), and haloalkyl means alkyl substituted with the above-mentioned halogen. For example, halomethyl means methyl (-CH ₂ X, -CHX ₂ or -CX ₃ ) where at least one of the hydrogens of methyl is replaced with halogen.

In general, silicon compounds used as additives have the effect of protecting silicon oxide films from phosphoric acid aqueous solutions, but there is a problem in that silicon compounds and silicon impurities generated after etching combine to form particles, which contaminate the silicon substrate.

Silane compounds in which a hydrophilic functional group is bonded to a silicon atom can be easily decomposed at low temperatures by reaction with water, forming a silicon-hydroxyl group (-Si-OH). The silicon-hydroxyl group forms a siloxane (-Si-O-Si-) group in which silicon atoms and oxygen atoms alternately bond through polymerization to form a random chain structure. Silane compounds containing siloxane groups eventually grow and precipitate as silicon particles in which the siloxane groups are repeatedly polymerized, which causes a problem in that storage stability is reduced.

A silicon nitride film etching solution according to one embodiment of the present invention includes a compound represented by the following chemical formula 1 to suppress particle generation.

[Chemical Formula 1]

In the above chemical formula 1,

X ₁ to X ₃ are each independently selected from C ₁ -C ₂₀ alkoxy, a hydroxy group and a halogen, and R ₁ to R ₃ are each independently selected from hydrogen, a C ₁ -C ₂₀ alkyl group, a C6-C12 cycloalkyl, a C2-C10 heteroalkyl comprising at least one heteroatom, a C ₂ -C ₁₀ alkenyl, a C ₂ -C ₁₀ alkynyl, a C ₁ -C ₁₀ haloalkyl, a C ₁ -C ₁₀ aminoalkyl, aryl, heteroaryl, aralkyl and halogen.

Here, the compound represented by the chemical formula 1 of the present invention exhibits a ring form, thereby maintaining the compound structure until reaching a high temperature. Accordingly, by reducing the phenomenon in which the silicon-hydroxyl group changes into a siloxane (-Si-O-Si-) compound through polymerization, particle generation can be suppressed.

In addition, a silicon nitride film etching solution according to one embodiment of the present invention includes a compound represented by chemical formula 1 to increase the reactivity with a hydroxyl group (-OH) of a silicon oxide film, thereby increasing the etching selectivity for a silicon nitride film compared to a silicon oxide film.

Specifically, the compound represented by Chemical Formula 1 included in the silicon nitride film etching solution forms a passivation layer of the silicon oxide film through an SN2 (Bimolecular Nucleophilic Substitution) reaction with a hydroxyl group (-OH) of the silicon oxide film. That is, in order to sufficiently form the passivation layer of the silicon oxide film, the SN2 reactivity of the compound with the hydroxyl group (-OH) must be increased. Specifically, as the compound structure becomes more unstable, the SN2 reactivity with the hydroxyl group (-OH) may increase, and thus the reactivity of the compound with the hydroxyl group (-OH) may be determined depending on the degree of stability of the compound structure.

Cyclic compounds that can be used as additives in silicon nitride film etching solutions can exhibit cis or trans forms in terms of stereochemical structure.

For example, a compound in the form of cis can undergo a reaction according to the following reaction scheme 1 under etching conditions.

[Reaction Formula 1]

As shown in the above reaction scheme 1, a cis-form compound can react with a phosphoric acid aqueous solution under etching conditions, and a ^cation can be added to the hydroxyl group (-OH). By adding the cation, the hydroxyl group (-OH) exhibits -OH ₂₊ , and an SN2 reaction can proceed between the hydroxyl group ( ^-OH ) and -OH ₂₊ within the molecule.

However, in the cis form of compounds ^, the leaving group -OH ₂₊ and the nucleophile hydroxyl group (-OH) are not arranged axially. That is, all the hydroxyl groups (-OH) in the cis form of compounds are arranged only in the equatorial direction with ^the leaving group -OH ₂₊ , making it difficult for the SN2 reaction ^to proceed between the hydroxyl group (-OH) and -OH ₂₊ in the molecule in the cis form of compounds.

Here, the compound represented by the chemical formula ¹ of the present invention can undergo an SN2 reaction with the hydroxyl group (-OH) and -OH ₂₊ within the molecule.

For example, the compound represented by chemical formula 1 of the present invention can be represented by a compound represented by chemical formula 2 or chemical formula 3 below.

[Chemical formula 2]

[Chemical Formula 3]

In the above chemical formulas 2 and 3, R ₁ to R ₃ are each independently selected from hydrogen, a C ₁ -C ₂₀ alkyl group, a C6-C12 cycloalkyl, a C6-C30 aryl, and halogen.

In addition, as an example, a trans form compound represented by the chemical formula 2 may undergo a reaction according to the following reaction formula 2 under etching conditions.

[Reaction Formula 2]

As shown in the above reaction scheme 2, the trans form compound of the present invention can react with an aqueous phosphoric acid solution under etching conditions in the same manner as the cis form compound, so that a cation is added to the hydroxyl group (-OH).

However, in the trans form of the compound of the present invention, unlike the cis form of the compound ^, the leaving group -OH ₂₊ and the nucleophile hydroxyl group ⁽ -OH) are arranged in the axial direction. Accordingly, the trans form of the compound forms an unstable Si-O-Si structure due to the SN2 reaction between the hydroxyl group (-OH) and -OH ₂₊ within the molecule.

Here, the compound in the trans form can have increased SN2 reactivity with the hydroxyl group (-OH) on the surface of the silicon oxide film as an unstable Si-O-Si structure is formed within the molecule.

Specifically, a compound including the above-mentioned unstable Si-O-Si structure and a hydroxyl group (-OH) on the surface of a silicon oxide film can react according to the following reaction formula 3.

[Reaction Formula 3]

As shown in the above reaction scheme 3, the compound including the unstable Si-O-Si structure exhibits a high bond angle strain. Accordingly, the compound has increased SN2 reactivity with the hydroxyl group (-OH) on the surface of the silicon oxide film, and can easily bond with the hydroxyl group (-OH) on the surface of the silicon oxide film.

That is, the compound combined with the hydroxyl group (-OH) on the surface of the silicon oxide film forms a passivation layer of the silicon oxide film, thereby lowering the etching rate for the silicon oxide film, thereby improving the etching selectivity for the silicon nitride film compared to the silicon oxide film.

The additive including the compound represented by the chemical formula 1 described above is preferably present in the silicon nitride film etching solution at 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, expressed in units of ppm. For example, if the additive is present at 5,000 ppm in the silicon nitride film etching solution, it will mean that the dissolved additive in the silicon nitride film etching solution is 5,000 ppm. If the additive is present in the silicon nitride film etching solution at less than 50 ppm, the amount of the additive may not be sufficient under etching conditions, and thus the effect of increasing the etching selectivity for the silicon nitride film relative to the silicon oxide film may be insignificant. On the other hand, if the additive in the silicon nitride film etching solution exceeds 200,000 ppm, a problem of generating a large amount of silicon-based particles may occur due to an increase in the saturation concentration of the additive in the silicon nitride film etching solution.

In addition, it is preferable that the content of the trans compound represented by the chemical formula 1 among the additives is 50% or more. More preferably, the content of the trans compound represented by the chemical formula 1 among the additives is 90% or more. When the content represented by the chemical formula 1 among the additives is less than 50%, the reactivity with the hydroxyl group (-OH) on the surface of the silicon oxide film under etching conditions may decrease. Accordingly, the protective layer of the silicon oxide film cannot be sufficiently formed, and the effect of increasing the etching selectivity for the silicon nitride film compared to the silicon oxide film may be minimal. That is, the higher the content ratio of the trans compound represented by the chemical formula 1 among the additives, the more the protective layer of the silicon oxide film can be sufficiently formed, thereby improving the etching selectivity for the silicon nitride film compared to the silicon oxide film.

The silicon substrate, which is the etching target of the silicon nitride film etching solution according to the present invention, preferably includes at least a silicon oxide film (SiO _x ), and may include a silicon oxide film and a silicon nitride film at the same time. In addition, in the case of a silicon substrate including a silicon oxide film and a silicon nitride film at the same time, the silicon oxide films and the silicon nitride films may be alternately laminated or may be laminated in different areas.

Here, the silicon oxide film is classified into SOD (Spin On Dielectric) film, HDP (High Density Plasma) film, thermal oxide film, BPSG (Borophosphate Silicate Glass) film, PSG (Phospho Silicate Glass) film, BSG (BoroSilicate Glass) film, PSZ (Polysilazane) film, FSG (Fluorinated Silicate Glass) film, LP-TEOS (Low Pressure TetraEthyl Ortho Silicate) film, PETEOS (Plasma Enhanced Tetra Ethyl Ortho Silicate) film, HTO (High Temperature Oxide) film, MTO (Medium Temperature Oxide) film, USG (Undopped Silicate Glass) film, SOG (Spin On Glass) film, APL (Advanced Planarization Layer) film, ALD (Atomic Layer Deposition) film, PE-oxide film (Plasma Enhanced oxide) or O It can be mentioned as ₃ -TEOS (O ₃ -Tetra Ethyl Ortho Silicate).

Here, the phosphoric acid aqueous solution is a component that etches the silicon nitride film while maintaining the pH of the etching solution, thereby suppressing various forms of silicon compounds present in the etching solution from changing into silicon particles.

In one embodiment, it is preferable that the phosphoric acid aqueous solution is included in an amount of 60 to 90 parts by weight per 100 parts by weight of the silicon nitride film etching solution.

If the content of the phosphoric acid aqueous solution is less than 60 parts by weight per 100 parts by weight of the silicon nitride film etching solution, there is a concern that the etching speed of the silicon nitride film may decrease, so that the silicon nitride film may not be sufficiently etched or the process efficiency of the etching of the silicon nitride film may decrease.

On the other hand, if the content of the phosphoric acid aqueous solution exceeds 90 parts by weight per 100 parts by weight of the silicon nitride film etching solution, the increase in the etching rate of the silicon oxide film is greater than the increase in the etching rate of the silicon nitride film, so that the etching selectivity for the silicon nitride film may decrease compared to the silicon oxide film, and defects in the silicon substrate may occur due to the etching of the silicon oxide film.

A silicon nitride film etching solution according to one embodiment of the present invention may further include a fluorine-containing compound to compensate for the etching rate of the silicon nitride film that is reduced due to the use of an additive while improving the efficiency of the overall etching process.

As used herein, the term “fluorine-containing compound” refers to any form of compound capable of dissociating fluorine ions.

In one embodiment, the fluorine-containing compound is at least one selected from hydrogen fluoride, ammonium fluoride, ammonium difluoride, and ammonium bifluoride.

Additionally, 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 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 of the alkyl group is as described above.

In another example, the fluorine-containing compound may be an ionic liquid in which an organic cation selected from alkylpyrrolium, alkylimidazolium, alkylpyrazolium, alkyloxazolium, alkylthiazolium, alkylpyridinium, alkylpyrimidinium, alkylpyridazinium, alkylpyrazinium, alkylpyrrolidinium, alkylphosphonium, alkylmorpholinium, and alkylpiperidinium is ionically bonded to a fluorine anion selected from fluorophosphate, fluoroalkyl-fluorophosphate, fluoroborate, and fluoroalkyl-fluoroborate.

Compared to hydrogen fluoride or ammonium fluoride, which are commonly used as fluorine-containing compounds in silicon nitride film etching solutions, fluorine-containing compounds provided in the form of ionic liquids have high boiling points and decomposition temperatures, and thus have the advantage of being less likely to change the composition of the etching solution due to decomposition during the etching process performed at high temperatures.

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

According to the present manufacturing method, it is possible to manufacture a semiconductor device by performing a selective etching process on a silicon nitride film using the above-described etching solution on a silicon substrate including at least a silicon nitride film (SI _x N _y ).

A silicon substrate used in the manufacture of semiconductor devices may include a silicon nitride film (SI _x N _y ) or may include a silicon oxide film and a silicon nitride film at the same time. In addition, in the case of a silicon substrate including a silicon oxide film and a silicon nitride film at the same time, the silicon oxide films and the silicon nitride films may be alternately laminated or may be laminated in different areas.

The method for manufacturing a semiconductor device according to the present invention can be applied to a manufacturing process of a NAND device. More specifically, in a process step where selective removal of a silicon nitride film without loss of a silicon oxide film is required among the laminated structures for forming a NAND, the process can be performed by using the etching solution described above.

As an example, FIG. 1 is a schematic cross-sectional view illustrating a silicon nitride film removal process 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 a trench (50) is formed through an anisotropic etching process.

In addition, referring to FIG. 1, an etching solution according to the present invention is injected through a trench (50) region formed in a laminated structure (20), whereby the silicon nitride film (11) is etched, leaving only the silicon oxide film (12) and the mask pattern layer (30).

That is, the present invention uses an etching solution having an improved etching selectivity for a silicon nitride film compared to a silicon oxide film, thereby minimizing the etching of a silicon oxide film (12) in a laminated structure (20) and completely and selectively removing a silicon nitride film (11) for a sufficient period of time. Thereafter, a semiconductor device can be manufactured through a subsequent process including a step of forming a gate electrode in an area where the silicon nitride film (11) has been removed.

<silicon Nitride film Etching Method for preparing solution>

According to one aspect of the present invention, a method for producing a silicon nitride film etching solution is provided, including the steps of: (a) mixing a silicon compound precursor and water to prepare a mixed solution, and then adding a hydroxide to the mixed solution to synthesize a silicon compound, (b) extracting an aqueous solution of the silicon compound synthesized in step (a) with a first organic solvent, and then removing the first organic solvent, (c) mixing the resultant product of step (b) with a second organic solvent and refluxing, (d) lowering the temperature of the resultant product of step (c) to a temperature range of 30° C. to -40° C. to separate a crystallized solid compound, and (e) mixing the solid compound of step (d) with an aqueous phosphoric acid solution to prepare a mixed solution.

First, the manufacturing method of the present invention includes the step of (a) mixing a silicon compound precursor and water to prepare a mixture, and then adding hydroxide to the mixture to synthesize a silicon compound.

The above silicon compound precursor is preferably a trialkoxysilane compound. For example, the trialkoxysilane compound may be selected from 3-(2-Aminoethylamino)propyltrimethoxysilane, Allyltrimethoxysilane, and 3-(Trimethoxysilyl)propyl Acrylate. The hydroxide is not particularly limited as long as it is a compound capable of providing hydroxide ions, and may be, for example, LiOH, NaOH, KOH, Be(OH) ₂ , Mg(OH) ₂ , or Ca(OH) ₂ .

Additionally, 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 manufacturing method of the present invention includes the step (b) of extracting an aqueous solution of the silicon compound synthesized in step (a) with a first organic solvent and then removing the first organic solvent.

More specifically, the silicon compound synthesized by step (a) can be mixed with water to prepare an aqueous solution of the silicon compound, and extracted with a first organic solvent. For example, the first organic solvent can be selected from ethyl acetate, dichloromethane, chloroform, hexane, toluene, and ether.

The aqueous solution of the above silicon compound is extracted with a first organic solvent, and then the first organic solvent is removed. The method for removing the first organic solvent is not particularly limited, and for example, the first organic solvent can be removed using a rotary evaporator.

Next, the manufacturing method of the present invention includes a step (c) of mixing the resultant product of step (b) with a second organic solvent and refluxing the mixture.

More specifically, the silicon compound extracted by step (b) and the second organic solvent can be mixed and refluxed at a high temperature. In step (c), both the silicon compound exhibiting cis stereochemistry and the silicon compound exhibiting trans stereochemistry extracted by step (b) can be dissolved in the second organic solvent. The type of the second organic solvent is not particularly limited, and may be, for example, hexene, benzene, or isopropyl methyl ether.

Next, the manufacturing method of the present invention includes a step of (d) lowering the resultant of step (c) to a temperature range of 30° C. to -40° C. to separate a crystallized solid compound.

More specifically, by step (c), the silicon compound exhibiting cis and trans stereochemistry dissolved in a nonpolar solvent can be lowered to a low temperature range of 30° C. to -40° C. to separate the crystallized solid compound. Here, even when the temperature is changed to low, the silicon compound exhibiting cis stereochemistry is still dissolved in the nonpolar solvent, whereas the silicon compound exhibiting trans stereochemistry can be crystallized and exist as a solid compound. Accordingly, the silicon compound exhibiting trans stereochemistry, which is a crystallized solid compound, can be separated from the silicon compound exhibiting cis stereochemistry.

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

The phosphoric acid aqueous solution can maintain the pH of the etching solution and suppress the silicon compound present in the etching solution from changing into silicon particles. For example, it is preferable that the phosphoric acid aqueous solution is included in an amount of 60 to 90 parts by weight per 100 parts by weight of the mixed solution.

When using an etching solution manufactured according to the manufacturing method of the present invention described above, the etching speed of a silicon oxide film using a phosphoric acid aqueous solution can be reduced, and the etching selectivity for a silicon nitride film compared to a silicon oxide film can be improved.

Hereinafter, specific embodiments of the present invention are presented. However, the embodiments described below are only intended to specifically illustrate or explain the present invention, and the present invention should not be limited thereto.

Example

Etching Preparation of solution

Example 1

A silicon nitride film etching solution was prepared by mixing 85 wt% phosphoric acid, 50 ppm additive, and the balance of water. The additive includes the following cis form of compound 1 and trans form of compound 2, and the content ratio of compound 1 and compound 2 is 9:1.

[Compound 1]

[Compound 2]

Example 2

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

Example 3

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

Example 4

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

Example 5

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

Comparative example 1

A silicon nitride film etching solution was prepared in the same manner as in Example 1, except that only compound 1 of Example 1 was included in the additive.

Experimental example

A silicon nitride film etching solution having a composition according to each of Examples 1 to 5 and Comparative Example 1 was used to etch a 500 Å thick silicon oxide film (thermal oxide layer) and a silicon nitride film by immersing them in the heated etching solution at 175°C for 10 minutes.

The thickness of the silicon oxide and silicon nitride films before and after etching was measured using ellipsometry (Nano-View, SE MG-1000; Ellipsometery), and the etching rate was calculated by dividing the difference in thickness of the silicon oxide and silicon nitride films before and after etching by the etching time (10 minutes).

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

Silicon oxide film
Etching rate ( /min) Silicon nitride film
Etching rate ( /min) Etch selectivity
(Silicon nitride film etching rate/Silicon oxide film etching rate) Example 1 1.55 94.11 60.72 Example 2 1.24 95.16 76.74 Example 3 0.88 93.33 106.07 Example 4 0.61 95.88 157.18 Example 5 0.24 94.70 394.58 Comparative Example 1 1.69 94.01 55.63

As shown in Table 1 above, the silicon nitride film etching solutions of Examples 1 to 5 can lower the etching rate for the silicon oxide film compared to the silicon nitride film etching solution of Comparative Example 1, and accordingly, it can be confirmed that the etching selectivity for the silicon nitride film compared to the silicon oxide film is improved.

In particular, as shown in Table 1 above, the higher the content ratio of the trans-form compound among the additives, the more the etching rate for the silicon oxide film can be reduced, and accordingly, it can be confirmed that the etching selectivity for the silicon nitride film compared to the silicon oxide film is further improved.

Above, one embodiment of the present invention has been described, but those skilled in the art will be able to modify and change the present invention in various ways by adding, changing, deleting or adding components, etc., within the scope that does not depart from the spirit of the present invention described in the claims, and this will also be considered to be included within the scope of the 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; and
A compound represented by the following chemical formula 1; comprising:
Silicon nitride film etching solution:
[Chemical Formula 1]

In the above chemical formula 1,
X ₁ to X ₃ are each a hydroxy group,
Two of the above X ₁ to X ₃ exhibit a trans form in stereochemical structure,
R ₁ to R ₃ are each independently selected from hydrogen, a C ₁ -C ₂₀ alkyl group, a C ₆ -C ₁₂ cycloalkyl, aryl, and halogen.
In the first paragraph,
A silicon nitride film etching solution characterized in that the compound represented by the chemical formula 1 is a compound represented by the following chemical formula 2 or chemical formula 3:
[Chemical formula 2]

[Chemical Formula 3]

In the above chemical formulas 2 and 3, R ₁ to R ₃ are each independently selected from hydrogen, a C ₁ -C ₂₀ alkyl group, a C ₆ -C ₁₂ cycloalkyl, a C ₆ -C ₃₀ aryl, and halogen.
In the first paragraph,
The additive containing the compound represented by the chemical formula 1 in the silicon nitride film etching solution is characterized in that it is contained in an amount of 50 to 200,000 ppm.
Silicon nitride film etching solution.
In the first paragraph,
The above silicon nitride film etching solution further comprises at least one fluorine-containing compound selected from hydrogen fluoride, ammonium fluoride, ammonium bifluoride and ammonium bifluoride.
Silicon nitride film etching solution.
In the first paragraph,
The above silicon nitride film etching solution further contains a fluorine-containing compound having an organic cation and a fluorine anion in an ionic bonded form.
Silicon nitride film etching solution.
Phosphoric acid solution;
Compound 1 having the following structure; and
Compound 2 having the following structure;
The above compounds 1 and 2 are mixed in a ratio of 1:9 to 9:1.
Silicon nitride film etching solution:
[Compound 1]

[Compound 2]
.
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