KR20180004870A - Etching solution for silicon substrate - Google Patents

Abstract

The present invention relates to an etching solution for a silicon substrate and, more specifically, to an etching solution for a silicon substrate, capable of increasing a selection ratio with respect to a silicon nitride film to a silicon oxide film when the silicon nitride film is etched, and preventing silicon-based particles from being generated as an extra silicon additive is not used in the etching solution. To this end, an etching solution for a silicon substrate comprises an inorganic aqueous solution, and N-alkyl heterocyclic quaternary ammonium salts.

Description

{ETCHING SOLUTION FOR SILICON SUBSTRATE}

More particularly, the present invention relates to a silicon substrate etching solution, and more particularly, to a silicon nitride film having a higher selectivity for a silicon nitride film than a silicon oxide film, and a silicon additive is not used in the etching solution, To a silicon substrate etching solution.

There are various methods of etching the silicon nitride film and the silicon oxide film at present, but dry etching and wet etching are mainly used.

The dry etching method is usually a gas etching method, but isotropic is superior to the wet etching method. However, the wet etching method is widely used because the productivity is much lower than the wet etching method and the method is expensive.

In general, a wet etching method using phosphoric acid as an etching solution is well known, and etching of a silicon nitride film by phosphoric acid proceeds through the following chemical reaction.

4H ₃ PO ₄ + 3Si ₃ N ₄ + 27H ₂ O 4 (NH ₄ ) ₃ PO ₄ + 9H ₂ SiO ₃

When only pure phosphoric acid is used for etching the silicon nitride film, problems such as various defects and pattern abnormalities may be caused by etching the silicon nitride film as well as the silicon nitride film as the device is miniaturized. Therefore, the etching rate of the silicon oxide film is further lowered There is a need.

On the other hand, an attempt has been made to use a fluorine-containing compound as an additive to further increase the etching rate of the silicon nitride film, but fluorine has a disadvantage of increasing the etching rate to the silicon oxide film.

Recently, silicon additives have been used together with phosphoric acid in order to increase the etching rate of the silicon nitride film and lower the etching rate of the silicon oxide film.

However, since the silane compound mainly used as a silicon additive is basically low in solubility in an etching solution containing phosphoric acid, a hydrophilic functional group (for example, a hydroxyl group ) Are combined with each other.

When a silane compound in which a hydrophilic functional group is bonded to a silicon atom is used as a silicon additive, the appropriate solubility of the silane compound in the etching solution can be secured, but some problems arise.

First, if the concentration of the silane compound in the etching solution is increased to increase the selectivity to the silicon nitride film for the silicon oxide film, the etching rate of the silicon nitride film may be lowered depending on the increased silicon concentration in the etching solution .

That is, when the silicon additive is used, the etching rate is controlled according to the principle of chemical equilibrium in Le Chatelier by increasing the concentration of silicon in the etching solution. However, when the concentration of silicon is increased to an appropriate level or higher, In addition, the etching rate for the silicon nitride film is lowered and the productivity is lowered.

Secondly, the use of a silane compound as a silicon additive can result in an increased silicon concentration in the etch solution acting as the source (nucleus or seed) of the silicon-based particles, and the silicon-based particles generated during etching or post- Which is the largest cause of defects.

For example, a hydrophilic functional group bonded to a silicon atom may be replaced with a hydroxy group to form a silicon-hydroxy group (-Si-OH) either during etching or during cleaning with H ₂ O, and the silicon- (-Si-O-Si-) group in which a silicon atom and an oxygen atom alternately combine to form a random chain structure.

Silane compounds containing siloxane groups result in the growth and precipitation of the siloxane groups as repeatedly polymerized silicon-based particles, and the silicon-based particles remain on the silicon substrate, causing defects in devices implemented on the substrate, (E. G., A filter) and cause equipment failure.

Therefore, it is necessary to develop a silicon substrate etching solution which can realize a high selectivity to the silicon nitride film compared to the silicon oxide film during the etching of the silicon nitride film, and prevent generation of silicon particles during etching or cleaning after etching.

An object of the present invention is to provide a silicon substrate etching solution capable of realizing a high selectivity to a silicon nitride film in comparison to a silicon oxide film in etching a silicon nitride film.

Another object of the present invention is to provide a silicon substrate etching solution which does not use a silicon additive unlike a conventional silicon substrate etching solution and can prevent the etching rate from being lowered by use of a silicon additive.

In addition, the present invention provides a silicon substrate etching solution which can prevent generation of silicon-based particles during etching or cleaning depending on use of a silicon additive by not using a silicon additive unlike a conventional silicon substrate etching solution .

According to an aspect of the present invention, there is provided a silicon substrate etching solution comprising an inorganic acid aqueous solution and an N-alkyl heterocyclic quaternary ammonium salt. have.

The inorganic acid aqueous solution may be an aqueous solution containing at least one inorganic acid selected from sulfuric acid, nitric acid, phosphoric acid, silicic acid, hydrofluoric acid, boric acid, hydrochloric acid, perchloric acid, phosphoric anhydride, pyrophosphoric acid and polyphosphoric acid.

In one embodiment, the N-alkylheterocyclic quaternary ammonium salt may be represented by the following formula (1) or (2).

[Chemical Formula 1]

(2)

Wherein A is a saturated or unsaturated C ₂ -C ₂₀ ring optionally containing at least one heteroatom, R and R 'are each independently selected from C ₁ -C ₁₀ alkyl, C ₆ -C ₁₂ cycloalkyl, C ₂ -C ₁₀ heteroalkyl containing one heteroatom, C ₂ -C ₁₀ alkenyl or C ₂ -C ₁₀ alkynyl, and X is halogen.

In this case, the N-alkylheterocyclic quaternary ammonium salt may be prepared by reacting a silicon-hydroxyl group (-Si-OH) present on the surface of a silicon substrate with a silicon-alkoxy group (-Si-OR or -Si-OR ') By substitution, it is possible to form a passivation layer on the silicon oxide film.

In another embodiment, the N-alkylheterocyclic quaternary ammonium salt may be an aromatic compound represented by the following formula (3) or (4).

(3)

(3)

Here, X ₁ to X ₉ are each independently selected from carbon, nitrogen, oxygen or sulfur.

The silicon substrate etching solution according to the present invention may further comprise a fluorine-containing compound, wherein the fluorine-containing compound is at least one selected from hydrogen fluoride, ammonium fluoride, ammonium fluoride, ammonium hydrogen fluoride, A compound having a form in which a cation and a fluorine-based anion are ionically bonded.

Since the silicon substrate etching solution according to the present invention uses N-alkylheterocyclic quaternary ammonium salts, it is possible to form a protective film on the silicon oxide film without using the silicon additive, thereby increasing the selectivity to the silicon nitride film compared to the silicon oxide film.

Further, according to the present invention, unlike the conventional etching solution, the silicon additive is not used, so that there is no problem that the etching rate of the silicon substrate is lowered by using the silicon additive.

Further, according to the present invention, unlike the conventional etching solution, since no silicon additive is used, it is possible to prevent the failure of the silicon substrate or the failure of the etching and cleaning apparatus caused by the generation of the silicon-based particles during etching or cleaning after etching .

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described hereinafter. It should be understood, however, that the invention is not limited to the disclosed embodiments, but is capable of many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims.

Hereinafter, the silicon substrate etching solution according to the present invention will be described in detail.

According to an aspect of the present invention, a silicon substrate etching solution containing an inorganic acid aqueous solution and an N-alkyl heterocyclic quaternary ammonium salt may be provided.

Here, the inorganic acid aqueous solution may be an aqueous solution containing at least one inorganic acid selected from sulfuric acid, nitric acid, phosphoric acid, silicic acid, hydrofluoric acid, boric acid, hydrochloric acid and perchloric acid. In addition to the above-mentioned inorganic acids, phosphoric anhydride, pyrophosphoric acid or polyphosphoric acid may be used.

The inorganic acid aqueous solution is a component that maintains the pH of the etching solution to inhibit various types of silane compounds present in the etching solution from changing into silicon-based particles.

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

When the content of the inorganic acid aqueous solution is less than 60 parts by weight based on 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 process efficiency of etching the silicon nitride film is lowered.

On the other hand, when the content of the inorganic acid aqueous solution is more than 90 parts by weight based on 100 parts by weight of the silicon substrate etching solution, not only the etching rate of the silicon nitride film is excessively increased but also the silicon nitride film The selectivity may be lowered, and the silicon substrate may be defective due to the etching of the silicon oxide film.

The silicon substrate etching solution according to an embodiment of the present invention includes an N-alkylheterocyclic quaternary ammonium salt represented by the following formula (1) to increase the selectivity to the silicon nitride film versus the silicon oxide film.

As indicated by the following formulas (1) and (2), the N-alkylheterocyclic quaternary ammonium salt is defined herein as a cyclic compound in the form of a salt containing a nitrogen atom as a hetero atom, Nitrogen atoms are alkylated and exist in quaternary ammonium form.

[Chemical Formula 1]

(2)

The N-alkylheterocyclic quaternary ammonium salt is in the form of a salt having a positive charge, and it is possible to secure sufficient solubility in a silicon substrate etching solution containing an inorganic acid aqueous solution.

In addition, N-alkylheterocyclic quaternary ammonium salts are capable of forming relatively strong polar interactions with silicon substrates, particularly silicon oxide films.

The N-alkylheterocyclic quaternary ammonium salt adhered to the surface of the silicon oxide film through strong polar interaction can serve to prevent etching from the inorganic acid or the fluorine-containing compound of the silicon oxide film.

Wherein A is a saturated or unsaturated C ₂ -C ₂₀ single or multiple ring optionally comprising at least one heteroatom.

If A is a C ₂ -C ₂₀ ring (hydrocarbon ring) that does not contain a heteroatom, the N-alkyl heterocyclic quaternary ammonium salt may be provided as a three to twenty atomic ring configuration comprising nitrogen as a heteroatom .

Here, the ring may be a single ring or multiple rings. Also, the multiple rings may take the form in which at least two rings are bonded to each other, or at least two rings may be covalently bonded through a sigma bond.

For example, A may have a saturated or unsaturated ring containing a nitrogen atom that is alkyl-substituted and positively charged to form a saturated or unsaturated ring. Representative examples of A having this form include indole, quinoline, and the like.

In addition, the ring may be saturated or unsaturated, and when it is an unsaturated ring, the N-alkylheterocyclic quaternary ammonium salt is preferably provided as an aromatic compound form (i.e., an N-alkylheteroaryl quaternary ammonium salt) .

In addition, the N-alkylheterocyclic quaternary ammonium salt may further comprise at least one heteroatom in addition to the alkylated nitrogen atom. Wherein the heteroatom is selected from nitrogen, oxygen or sulfur. In addition to the alkylated nitrogen atom, additional heteroatoms included in the ring may also be alkylated.

For example, the N-alkylheterocyclic quaternary ammonium salt may be represented by the following formula (3) or (4).

(3)

[Chemical Formula 4]

Here, X ₁ to X ₉ represent a carbon or a hetero atom, and the hetero atom is selected from nitrogen, oxygen or sulfur.

The N-alkylheterocyclic quaternary ammonium salt herein provides a saturated or unsaturated ring containing nitrogen as a heteroatom to provide a stable or stable substitution or alkoxylation rate for the silicon oxide film relative to the N-alkyl quaternary ammonium salt in the chain form It is possible to secure.

In the case of the N-alkyl quaternary ammonium salt in the form of a chain, since the tetrahedral structure is formed based on the nitrogen atom, the quaternary ammonium salt of the N-alkylheterocyclic quaternary ammonium salt is formed on the surface of the silicon oxide film Lt; RTI ID = 0.0 > silicon-hydroxy < / RTI >

It is also possible that the positive charge of the N-alkyl quaternary ammonium salt in the form of a chain is stabilized by electron donating inductive effect or hyperconjugation by at least one alkyl group substituted at the nitrogen atom Therefore, a relatively large activation energy is required to transfer an alkyl group by a silicon-hydroxy group.

On the other hand, since the N-alkyl quaternary ammonium salt in the form of a saturated or unsaturated ring can take a ring-like planar structure, it is easy to adhere to the surface of the silicon oxide film, It is easy to transfer the substituted alkyl group to the silicon-hydroxy group.

In particular, when the N-alkylheterocyclic quaternary ammonium salt is an aromatic compound, the energy level of sigma * of the alkyl group may be lowered by the non-aromatic compound due to the aromaticity. In this case, the non-bonding nonspecific electron pairs existing in the oxygen atom of the silicon-hydroxyl group are easily transferred to the σ * of the alkyl group having a relatively low energy level compared to the non-aromatic compound, It is possible to cause covalent bond by inducing anti-bonding. Accordingly, when the N-alkylheterocyclic quaternary ammonium salt is an aromatic compound, the alkoxylation of the silicon-hydroxyl group can proceed more smoothly than in the case of the non-aromatic compound.

Further, when the N-alkylheterocyclic quaternary ammonium salt is an aromatic compound represented by the general formula (4), a state in which aromaticity is partially lost by multiple alkylation of nitrogen which is a hetero atom, It is possible to recover the aromaticity by breaking the covalent bond between the N-alkyl by transferring the non-bonding nonspecific electron pair present in the alkyl group σ *. Accordingly, the reaction can proceed smoothly in the direction in which the alkoxylation of the silicon-hydroxyl group takes place.

In addition, the N-alkyl quaternary ammonium salt in the form of a ring can transfer an alkyl group covalently bonded to nitrogen to the silicon-hydroxy group and at the same time eliminate the ring strain, The stabilization effect obtained when transferring to a silicon-hydroxy group is great. As a result, the energy barrier of the protection reaction of the silicon oxide film by the N-alkyl quaternary ammonium salt in the ring form relative to the ammonium salt of the chained structure is relatively low, so that the N-alkylheterocyclic quaternary It is possible to efficiently protect the silicon oxide film by using an ammonium salt.

In N-alkylheterocyclic quaternary ammonium salts, the nitrogen atom is in an alkylated state, wherein the alkyl group is defined as R or R '.

R and R ', which are alkyl groups herein, include C ₁ -C ₁₀ alkyl, C ₆ -C ₁₂ cycloalkyl, and C ₂ -C ₁₀ heteroalkyl including at least one heteroatom and, additionally, any adjacent C ₂ -C ₁₀ alkenyl or C ₂ -C ₁₀ alkynyl in which an unsaturated bond is present in the carbon.

X is a counter anion of an N-alkyl heterocyclic quaternary ammonium salt having a positive charge and is a halogen selected from fluoro (-F), chloro (-Cl), bromo (-Br) or iodo (-I) to be.

The C _a -C _b functional group herein 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, and the like. The straight chain or branched chain alkyl has 10 or fewer (for example, a straight chain of C ₁ -C ₁₀ , C ₃ -C ₁₀ ), preferably 4 or less, more preferably 3 or less carbon atoms .

Specifically, the alkyl is selected from the group consisting of methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, i-butyl, t-butyl, pent- Methylbut-2-yl, 2,2,2-trimethylet-1-yl, n-hexyl, n-heptyl and n - octyl.

Hydrocarbonycloalkyl or heterocycloalkyl containing heteroatom herein may be understood as cyclic structures of alkyl or heteroalkyl, respectively, unless otherwise defined.

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

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

In addition, cycloalkyl or heterocycloalkyl containing a heteroatom may have a form in which a cycloalkyl, heterocycloalkyl, aryl or heteroaryl is conjugated or linked by a covalent bond.

When R or R 'is alkenyl or alkynyl imidazol, alkenyl of sp ² - sp- the mixed carbon of the hybrid carbon or alkynyl-mixed carbon or alkynyl of sp ² hybrid of sp- alkenyl carbon is bonded directly or Al It may be indirectly coupled by a hybrid form of carbon - sp ³ in the combined alkyl.

Aryl herein, unless otherwise defined, means an unsaturated aromatic ring comprising a single ring or multiple rings (preferably one to four rings) joined together or covalently bonded to each other. Non-limiting examples of aryl include phenyl, biphenyl, terphenyl, m-terphenyl, p-terphenyl, 1-naphthyl, 2- naphthyl, Anthryl, 9-anthryl, phenanthrenyl, 2-phenanthrenyl, 3-phenanthrenyl, 4-phenanthrenyl, 9-phenanthrenyl, Pyrenyl and 4-pyrenyl.

As used herein, heteroaryl means a functional group in which at least one carbon atom in the aryl as defined above is replaced by a non-carbon atom such as nitrogen, oxygen or sulfur.

Non-limiting examples of heteroaryl include furyl, tetrahydrofuryl, pyrrolyl, pyrrolidinyl, thienyl, tetrahydrothienyl, oxazolyl, , Isoxazolyl, triazolyl, thiazolyl, isothiazolyl, pyrazolyl, pyrazolidinyl, oxadiazolyl, thiadiazolyl, thiadiazolyl, a thiadiazolyl group, an imidazolyl group, an imidazolinyl group, a pyridyl group, a pyridaziyl group, a triazinyl group, a piperidinyl group, a morpholinyl group, Thiomorpholinyl, pyrazinyl, piperainyl, pyrimidinyl, naphthyridinyl, benzofuranyl, benzothienyl, indolyl, and the like. , Indolinyl, indolizinyl, indazolyl, quinolizinyl, quinolinyl, iso Quinolinyl, quinolinyl, quinolinyl, cinnolinyl, phthalazinyl, quinazolinyl, quinoxalinyl, pteridinyl, quinuclidinyl, carbazoyl, acridinyl, Phenothiazinyl, phenothizinyl, phenoxazinyl, purinyl, benzimidazolyl, benzothiazolyl, and the like.

The silicon substrate, which is an object to be etched in the etching solution for a silicon substrate according to the present invention, preferably includes at least a silicon oxide film (SiO _x ), and the silicon oxide film and the silicon nitride film (Si _x N _y , SI _x O _y N _z ) . Also. In the case of a silicon substrate including a silicon oxide film and a silicon nitride film simultaneously, the silicon oxide film and the silicon nitride film may be alternately stacked or stacked in different regions.

Here, the silicon oxide film may be formed using a spin on dielectric (SOD) film, a high density plasma (HDP) film, a thermal oxide, a borophosphate silicate glass (BPSG) film, a phosphosilicate glass , A BSG (Borosilicate Glass) film, a PSZ (Polysilazane) film, a FSG (Fluorinated Silicate Glass) film, a LP-TEOS (Low Pressure Tetra Ethyl Ortho Silicate) film, a PETEOS (Plasma Enhanced Tetra Ethyl Ortho Silicate) An AlN (Atomic Layer Deposition) film, a PE-oxide (Plasma) oxide film, an AlGaN layer, an AlGaN layer, Enhanced oxide) or O ₃ -TEOS (O ₃ -Tetra Ethyl Ortho Silicate).

Generally, since many silicon particles or atoms constituting the silicon oxide film are present in a state substituted with a hydroxyl group (-OH), there is a fear that the silicon particles or atoms are grown as silicon-based particles during the etching or during cleaning after the etching.

Accordingly, in order to reduce the rate at which the silicon oxide film is etched by the inorganic acid during the etching and further reduce or suppress the generation of the silicon-based particles during the etching or cleaning after the etching, the etching solution according to the present invention is an N-alkylheterocyclic quaternary (-Si-OH) present on the surface of the silicon substrate is replaced or alkoxylated with a silicon-alkoxy group (-Si-OR or -Si-OR ' A protective film is formed on the surface of the substrate, particularly, the silicon oxide film.

As the silicon-hydroxyl group (-Si-OH) present on the surface of the silicon substrate is alkoxylated, additional hydroxylation may be limited. As a result, it is possible to reduce the growth of silicon particles having a hydroxy group in the form of silicic acid during etching or cleaning after etching, and furthermore, to prevent the silicon particles from being separated from the silicon substrate to grow and precipitate into silicon- .

As described above, since a protective film can be formed on the surface of the silicon oxide film by alkoxylating the silicon-hydroxyl group (-Si-OH), it is possible to reduce the etching rate of the silicon oxide film by inorganic acid or the like, The etching selectivity ratio of the silicon nitride film to the silicon oxide film can be prevented from decreasing even if the silicon oxide additive is not used in combination.

That is, the etching solution according to the present invention uses a silicon additive in that it uses an N-alkylheterocyclic quaternary ammonium salt instead of a silicon additive that can cause a reduction in the etching rate for the silicon nitride film and the generation of silicon-based particles It is possible to solve the problem that arises.

In addition, since the etching solution according to the present invention has a relatively complicated structure in the etching solution, there is no silicon additive that is difficult to separate. Therefore, pure inorganic acid can be easily separated and recycled from the etching solution used for etching. There is an advantage.

The N-alkylheterocyclic quaternary ammonium salt described above is preferably present in the silicon substrate etching solution at 200 to 50,000 ppm.

When the N-alkylheterocyclic quaternary ammonium salt is present in an amount less than 200 ppm in the silicon substrate etching solution, the protective effect on the silicon oxide film is insufficient, and the effect of increasing the selectivity to the silicon nitride film compared to the silicon oxide film may not be exhibited . On the other hand, when the N-alkylheterocyclic quaternary ammonium salt in the silicon substrate etching solution exceeds 50,000 ppm, the etching rate of the silicon nitride film is significantly lowered, and it may be difficult to increase the selectivity to the silicon nitride film compared to the silicon oxide film.

The silicon substrate etching solution according to an embodiment of the present invention may further include a fluorine-containing compound to improve the etching rate of the silicon nitride film. When the etching solution according to the present invention is used, since the silicon oxide film can be protected by the N-alkylheterocyclic quaternary ammonium salt, it is possible to prevent the etching rate of the silicon oxide film from being increased by the fluorine-containing compound .

The fluorine-containing compound herein refers to any type 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 fluoride, and ammonium hydrogen fluoride.

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

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

In another example, the fluorine-containing compound is selected from the group consisting of alkylpyrrolidium, alkylimidazolium, alkylpyrazolium, alkyloxazolium, alkylthiazolium, alkylpyridinium, alkylpyrimidinium, alkylpyridazinium, Fluoroalkyl-fluoroalkyl, fluoroalkyl-fluoroalkyl, fluoroalkyl-fluoroalkyl, fluoroalkyl-fluoroalkyl, fluoroalkyl-fluoroalkyl, fluoroalkyl-fluoroalkyl, fluoroalkyl-fluoroalkyl and fluoroalkyl-fluoroalkyl And the fluorine-based anion selected from fluoroborate may be an ionic liquid in the ion-bonded form.

Fluorine-containing compounds provided in ionic liquid form as compared with hydrogen fluoride or ammonium fluoride commonly used as fluorine-containing compounds in a silicon substrate etching solution have a high boiling point and a decomposition temperature and are decomposed in an etching process performed at a high temperature There is an advantage that the composition of the etching solution is less likely to change.

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

Experimental Example 1

Additives were added to 750 g of 85% phosphoric acid aqueous solution in the amounts shown in Table 1 below to prepare an etching solution.

division Silane compound (ppm) Quaternary ammonium salt (ppm) Fluorine-containing compound (ppm) Example 1 - 5,000 - Example 2 - 5,000 1,000 Comparative Example 1 1,000 - - Comparative Example 2 1,000 - 1,500

Here, the silane compound used in Comparative Example 1 and Comparative Example 2 was 3-aminopropyl silanetriol, and the quaternary ammonium salt used in Example 1 and Example 2 was N-methylpyridinium chloride, 2 and Comparative Example 2 is hydrofluoric acid (HF).

After the etching solution was heated to 165 ° C, a silicon oxide film (thermal oxide layer) and a silicon nitride film were etched for 3 minutes. The thicknesses of the silicon oxide and silicon nitride films before and after etching were measured using a Nano-View (SE MG-1000; Ellipsometry), and the measurement results are the average values of the five measurements. The etch rate is calculated by dividing the difference in thickness between the silicon oxide film and the silicon nitride film by etching time (3 minutes) before and after etching. After completion of the etching, the etching solution was analyzed by a particle size analyzer to measure the average diameter of the silicon particles present in the etching solution.

The measured etch rate and the average diameter of the silicon-based particles in the etching solution are shown in Table 2 below.

division Silicone-based particles
Average diameter (μm) Silicon oxide film
Etching speed (Å / min) Silicon nitride film
Etching speed (Å / min) Example 1 <0.01 1.23 60.01 Example 2 <0.01 4.15 180.91 Comparative Example 1 70 1.33 58.67 Comparative Example 2 117 3.59 171.34

As shown in Table 2, when the silane compound is used as in Comparative Example 1, it can be confirmed that the etching rate for the silicon oxide film and the silicon nitride film is generally reduced as compared with the embodiment. On the other hand, according to Comparative Example 1, it was confirmed that silicon-based particles having a size of several tens of micrometers were generated.

According to Comparative Example 2, the etching rate for the silicon oxide film and the silicon nitride film was generally increased compared to Comparative Example 1, and in particular, the etching rate for the silicon oxide film was increased, and silicon-based particles were also generated.

On the other hand, according to Examples 1 and 2, the silicon-based particles are present in a considerably small size or are hardly produced, and the selectivity to the silicon nitride film is also improved compared to the silicon oxide film.

Experimental Example 2

Additives were added to 750 g of 85% phosphoric acid aqueous solution in the amounts shown in Table 3 below to prepare an etching solution.

division Quaternary ammonium salt (ppm) Example 3 5,000 Example 4 5,000 Example 5 5,000 Example 6 5,000 Example 7 5,000 Comparative Example 3 5,000 Comparative Example 4 5,000 Comparative Example 5 5,000

In Example 4, 1,3-dimethylimidazolium chloride, Example 5, 4-dimethylmorpholinium chloride, and Example 6, 1-ethyl-2-pyrrolidinium chloride, Butyl-1-methylpyrrolidinium chloride, Example 7 used 1-ethyl-2-methylquinolinium chloride, Comparative Example 3 was benzenetrimethylammonium chloride, Comparative Example 4 was benzalkonium chloride , And Comparative Example 5 used phenyltrimethylammonium chloride.

 After the etching solution was heated to 165 ° C, a silicon oxide film (thermal oxide layer) and a silicon nitride film were etched for 3 minutes. The thicknesses of the silicon oxide and silicon nitride films before and after etching were measured using a Nano-View (SE MG-1000; Ellipsometry), and the measurement results are the average values of the five measurements. The etch rate is calculated by dividing the difference in thickness between the silicon oxide film and the silicon nitride film by etching time (3 minutes) before and after etching. After completion of the etching, the etching solution was analyzed by a particle size analyzer to measure the average diameter of the silicon particles present in the etching solution.

The measured etch rate and the average diameter of the silicon-based particles in the etching solution are shown in Table 4 below.

division Silicone-based particles
Average diameter (μm) Silicon oxide film
Etching speed (Å / min) Silicon nitride film
Etching speed (Å / min) Example 3 <0.01 1.23 60.01 Example 4 <0.01 1.55 59.68 Example 5 <0.01 1.47 61.98 Example 6 <0.01 1.33 62.21 Example 7 <0.01 1.67 60.19 Comparative Example 3 <0.01 2.79 57.67 Comparative Example 4 <0.01 2.49 58.79 Comparative Example 5 <0.01 2.11 62.17

As shown in Table 4, in Examples 3 to 7, it was confirmed that the silicon-based particles were present in a considerably small size or hardly produced, and the selectivity to the silicon nitride film was also improved compared to the silicon oxide film.

On the other hand, in the case of Comparative Examples 3 to 5, it was confirmed that almost no silicon-based particles were produced by using no silane compound as in the examples. However, unlike the examples, it was confirmed that the use of the N-alkyl quaternary ammonium salt in the form of a chain was insufficient to protect the silicon oxide film.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit of the invention as set forth in the appended claims. The present invention can be variously modified and changed by those skilled in the art, and it is also within the scope of the present invention.

Claims (12)

Inorganic acid aqueous solution; And
N-alkyl heterocyclic quaternary ammonium salts;
/ RTI &gt;
Silicon substrate etching solution.
The method according to claim 1,
Wherein the inorganic acid aqueous solution is an aqueous solution containing at least one inorganic acid selected from sulfuric acid, nitric acid, phosphoric acid, silicic acid, hydrofluoric acid, boric acid, hydrochloric acid, perchloric acid, phosphoric acid, pyrophosphoric acid,
Silicon substrate etching solution.
The method according to claim 1,
Wherein the N-alkylheterocyclic quaternary ammonium salt is a silicon substrate etching solution represented by the following Chemical Formula 1 or Chemical Formula 2:
[Chemical Formula 1]

(2)

Wherein A is a saturated or unsaturated C ₂ -C ₂₀ single or multiple ring optionally containing at least one heteroatom,
R and R 'are each independently C ₁ -C ₁₀ alkyl, C ₆ -C ₁₂ cycloalkyl, alkenyl, at least one hetero atom C ₂ -C ₁₀ heteroalkyl, C ₂ -C ₁₀ al containing or C ₂ - C ₁₀ is alkynyl,
And X is halogen)
The method of claim 3,
The N-alkylheterocyclic quaternary ammonium salt may be prepared by substituting a silicon-hydroxy group (-Si-OH) present on the surface of a silicon substrate with a silicon-alkoxy group (-Si-OR or -Si-OR ' ,
Silicon substrate etching solution.
The method of claim 3,
The N-alkylheterocyclic quaternary ammonium salt is an aromatic compound,
Silicon substrate etching solution.
The method of claim 5, wherein
The N-alkylheterocyclic quaternary ammonium salt is a silicon substrate etching solution represented by the following Chemical Formula 3 or Chemical Formula 4:
(3)

[Chemical Formula 4]

(Wherein X ₁ to X ₉ are each independently selected from carbon, nitrogen, oxygen or sulfur)
The method according to claim 1,
Wherein the N-alkylheterocyclic quaternary ammonium salt in the silicon substrate etching solution comprises 200 to 50,000 ppm,
Silicon substrate etching solution.
The method according to claim 1,
Further comprising a fluorine-containing compound,
Silicon substrate etching solution.
9. The method of claim 8,
Wherein the fluorine-containing compound is at least one selected from hydrogen fluoride, ammonium fluoride, ammonium fluoride, and ammonium hydrogen fluoride,
Silicon substrate etching solution.
9. The method of claim 8,
The fluorine-containing compound is a compound having a form in which an organic cation and a fluorine anion are ionically bonded,
Silicon substrate etching solution.
11. The method of claim 10,
The organic cations are selected from the group consisting of alkylammonium, alkylpyrrolidium, alkylimidazolium, alkylpyrazolium, alkyloxazolium, alkylthiazolium, alkylpyridinium, alkylpyrimidinium, alkylpyridazinium, alkylpyridinium, alkyl Pyrrolidinium, alkylphosphonium, alkylmorpholinium, and alkylpiperidinium.
Silicon substrate etching solution.
11. The method of claim 10,
The fluorine-based anion is selected from fluoride, fluorophosphate, fluoroalkyl-fluorophosphate, fluoroborate, and fluoroalkyl-fluoroborate.
Silicon substrate etching solution.