KR101778893B1 - 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 which provides a passivation effect on a silicon oxide film when a silicon nitride film is etched, thereby increasing the selectivity to the silicon nitride film compared to the silicon oxide film; and at the same time, does not use any additional silicon additive in the etching solution to prevent the generation of silicon-based particles.

Description

{ETCHING SOLUTION FOR SILICON SUBSTRATE}

The present invention relates to a silicon substrate etching solution, more particularly, to provide a passivation effect on a silicon oxide film during etching of a silicon nitride film, thereby increasing the selectivity to the silicon nitride film compared to the silicon oxide film, To a silicon substrate etching solution capable of preventing generation of silicon-based particles due to non-use.

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 compared to a silicon oxide film by imparting a passivation effect to the silicon oxide film when the silicon nitride film is etched.

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 S-hydrocarbyl thiophenium salt.

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 S-hydrocarbyl thiophene salt may be represented by the following formula (1).

[Chemical Formula 1]

here,

A is a saturated or unsaturated C ₂ -C ₂₀ single or multiple ring optionally containing at least one heteroatom,

R is substituted or unsubstituted C ₁ -C ₁₀ alkyl, substituted or unsubstituted C ₆ -C ₁₂ cycloalkyl, substituted or unsubstituted C ₂ -C ₁₀ heteroalkyl, substituted or unsubstituted C ₂ -C ₁₀ Substituted or unsubstituted C ₂ -C ₁₀ alkynyl, substituted or unsubstituted C ₁ -C ₁₀ haloalkyl, substituted or unsubstituted C ₁ -C ₁₀ aminoalkyl or substituted or unsubstituted C ₇ -C ₁₀ aralkyl, C ₃₀ aralkyl,

X is halogen.

At this time, the S-hydrocarbyl thiophene salt is obtained by substituting the silicon-hydroxyl group (-Si-OH) present on the surface of the silicon substrate or the silicon oxide film with the silicon-alkoxy group (-Si-OR) It is possible to form a passivation layer. Accordingly, even if a separate silicon additive such as a silane compound is not used, the silicon oxide film is etched to prevent the etch selectivity to the silicon nitride film from being lowered compared to the silicon oxide film.

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 S-hydrocarbyl thiophene salt is used in the silicon substrate etching solution according to the present invention, it is possible to increase the selectivity to the silicon nitride film compared to the silicon oxide film by forming a protective film on the silicon oxide film without using the silicon additive.

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 S-hydrocarbyl thiophenium 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 S-hydrocarbyl thiophene salt expressed by the following formula (1) to increase the selectivity to the silicon nitride film versus the silicon oxide film.

As used herein, thiophene refers to a heterocyclic compound containing sulfur (S) as a heteroatom.

The S-hydrocarbyl thiophene salt means a salt in which sulfur is positively charged by binding a hydrocarbyl group to sulfur, which is a hetero atom of thiophene, and is also referred to as S-hydrocarbyl thiophenium (thiophenium) .

Here, the hydrocarbyl group means a hydrocarbon functional group in which one hydrogen is removed from a hydrocarbon such as an alkane, an alkene, an alkane, a cycloalkane, an arene and the like and exists in a functional form.

The S-hydrocarbyl thiophene salt is obtained by substituting a silicon-hydroxyl group (-Si-OH) present on the surface of a silicon substrate or silicon oxide with a silicon-alkoxy group (-Si-OR) layer can be formed.

Accordingly, even if a separate silicon additive such as a silane compound is not used, the silicon oxide film is etched to prevent the etch selectivity to the silicon nitride film from being lowered compared to the silicon oxide film.

As indicated by the following formula 1, the S-hydrocarbyl thiophene salt is defined herein as a cyclic compound in the form of a salt containing a sulfur atom as a hetero atom, wherein the sulfur atom, which is a hetero atom, (alkylation) to form a tertiary salt.

[Chemical Formula 1]

The S-hydrocarbyl thiophene salt is in the form of a salt having a positive charge, and it is possible to ensure a sufficient solubility in a silicon substrate etching solution containing an inorganic acid aqueous solution.

In addition, S-hydrocarbyl thiophene salts can form relatively strong polarity interactions with silicon substrates, particularly silicon oxide films.

The S-hydrocarbyl thiophene 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 S-hydrocarbyl thiophene salt may be provided as a three to twenty-atom cyclic form containing sulfur as the sole 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 sulfur atom that is alkyl-substituted and positively charged to form a saturated or unsaturated ring. Representative examples of A having this form include thiophene, benzothiophene, and the like.

In addition, ring A can be saturated or unsaturated, and when it is an unsaturated ring, the S-hydrocarbyl thiophene salt can preferably be provided in the form of an aromatic compound (i.e., an S-hydrocarbyl heteroaryl thiophene salt) .

In addition, the S-hydrocarbyl thiophene salt may further comprise at least one heteroatom in addition to the hydrocarbylated sulfur atom. Wherein the heteroatom is selected from nitrogen, oxygen or sulfur. In addition to the hydrocarbylated sulfur atom, additional heteroatoms included in the ring may also be hydrocarbylated.

The S-hydrocarbyl thiophene salt herein is provided as a saturated or unsaturated cyclic form containing sulfur as a heteroatom, thereby stably securing the substitution or hydrocabylation rate of the silicon oxide film to the other chain type hydrocarbylated salt compound It is possible.

In the case of a hydrocarbylated salt compound in the form of a chain, a hydrocarbylated salt compound adheres to the surface of the silicon oxide due to a steric hindrance caused by forming a tetrahedral structure due to the formation of a tetrahedral structure based on the central atom, Hydroxy carbylation of the hydroxy group may be difficult.

In addition, the electron donating inductive effect or hyperconjugation by the other electron-donating functional group (for example, an alkyl group) substituted at the center atom of the positive charge of the hydrocarbylated salt compound in the form of a chain, It is necessary to have a relatively large activation energy to transfer the alkyl group to the silicon-hydroxy group.

On the other hand, since the S-hydrocarbyl thiophene salt in the form of a saturated or unsaturated ring can take a cyclic plane structure, it is easy to adhere to the surface of the silicon oxide film, It is easy to transfer a hydrocarbyl group substituted at an atom to a silicon-hydroxy group.

In particular, when the S-hydrocarbyl thiophene salt is an aromatic compound, the energy level of sigma * of the hydrocarbyl group can 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 S-hydrocarbyl thiophene salt is an aromatic compound, the hydrocarbylation of the silicon-hydroxyl group can proceed more smoothly than in the case of the non-aromatic compound.

In addition, the S-hydrocarbyl thiophene salt in the form of a ring can transfer a hydrocarbyl group covalently bonded to the sulfur to the silicon-hydroxy group and at the same time eliminate the ring strain or charge imbalance, A hydrocarbyl group substituted with a hydrocarbyl group is transferred to a silicon-hydroxy group.

As a result, the energy barrier of the silicon oxide film protection reaction by the S-hydrocarbyl thiophene salt in the ring form relative to the hydrocarbylated salt compound of the chained structure is relatively low. Therefore, the S- It is possible to efficiently protect the silicon oxide film by using an opene salt.

In the S-hydrocarbyl thiophene salt, the sulfur atom is in the hydrocarbylated state, wherein the hydrocarbyl group is defined as R.

Wherein R, which is an alkyl group, is substituted or unsubstituted C ₁ -C ₁₀ alkyl, substituted or unsubstituted C ₆ -C ₁₂ cycloalkyl, substituted or unsubstituted C ₂ -C ₁₀ heteroalkyl, substituted or unsubstituted C ₂ -C ₁₀ alkenyl, substituted or unsubstituted C ₂ -C ₁₀ alkynyl, substituted or unsubstituted C ₁ -C ₁₀ haloalkyl, substituted or unsubstituted C ₁ -C ₁₀ aminoalkyl, or substituted or unsubstituted a C ₇ -C ₃₀ aralkyl may be.

X is a counter anion of an S-hydrocarbyl thiophene salt having a positive charge and is a halogen selected from fluoro (-F), chloro (-Cl), bromo (-Br) or iodo (-I).

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.

An alkenyl or alkynyl functionality to the unsaturated bond is present between any two adjacent carbon, R is alkenyl or alkynyl imidazol time, the sp ² alkenyl - sp- mixed carbon is directly bonded to the carbon of the hybrid, or alkynyl Or may be in a form indirectly coupled by an sp ³ -hybridized carbon of alkyl bonded to the sp-hybrid carbon of the sp ² -hybridized or alkynyl of the alkenyl.

In addition, haloalkyl means alkyl substituted by the above-mentioned halogen. For example, halomethyl means methyl (-CH ₂ X, -CHX ₂ or -CX ₃ ) in which at least one of the hydrogens of methyl is replaced by halogen.

Aralkyl is a generic term for - (CH ₂ ) _n Ar, _wherein aryl is a functional group substituted in the carbon of the alkyl. Examples of aralkyl include benzyl (-CH ₂ C ₆ H ₅ ) or phenethyl (-CH ₂ CH ₂ C ₆ H ₅ ).

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.

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 of etching the silicon oxide film by the inorganic acid during the etching and further reduce or suppress the generation of the silicon-based particles during etching or cleaning after the etching, the etching solution according to the present invention may contain an S-hydrocarbyl thiophene salt (Si-OH) existing on the surface of a silicon substrate or a silicon oxide film by using a silicon-alkoxy group (-Si-OR) or by hydrocarbylating (alkoxylation) A protective film is formed on the surface of the oxide film.

Hydroxylation may be limited as the silicon-hydroxyl group (-Si-OH) present on the surface of the silicon substrate or the silicon oxide film becomes hydrocarbyl. 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- .

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

That is, the etching solution according to the present invention occurs in accordance with the use of a silicon additive in that S-hydrocarbyl thiophene salt is used instead of a silicon additive which may cause a lowering of an etching rate for a silicon nitride film and generation of silicon- The problem can be solved.

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 S-hydrocarbyl thiophene salt described above is preferably present in the silicon substrate etching solution at 200 to 50,000 ppm.

When the S-hydrocarbyl thiophene 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 S-hydrocarbyl thiophene salt exceeds 50,000 ppm in the silicon substrate etching solution, 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 S-hydrocarbyl thiophene salt, the etching rate of the silicon oxide film can be prevented from increasing 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 the form of ionic liquids as compared to 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) Thiophene salt (ppm) Fluorine-containing compound (ppm) Example 1 - 10,000 - Example 2 - 10,000 - Example 3 - 10,000 - Example 4 - 10,000 - Example 5 - 10,000 1,000 Comparative Example 1 - - - Comparative Example 2 1,000 - - Comparative Example 3 1,000 - 1,500

Here, the S-hydrocarbyl thiophene salt used in the examples is 1-methyl-benzothiophenium chloride (Example 1). Tetrahydro-1-methyl-thiophenium chloride (Example 2, Example 5), tetrahydro-1- (phenylmethyl) -thiophenium bromide (Example 3), tetrahydro- (Example 4).

The silane compound used in Comparative Example 2 and Comparative Example 3 was 3-aminopropyl silanetriol, and the fluorine-containing compound used in Example 5 and Comparative Example 3 was hydrofluoric acid (HF) The ammonium-based compound is trimethylphenyl ammonium 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 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 1.10 61.54 Example 3 <0.01 1.30 59.84 Example 4 <0.01 1.19 58.97 Example 5 <0.01 3.19 183.05 Comparative Example 1 <0.01 3.51 60.00 Comparative Example 2 70 1.33 58.67 Comparative Example 3 117 3.59 171.34

As shown in Table 2, when only phosphoric acid was used without containing any other additive in the etching solution as in Comparative Example 1, silicon-based particles were scarcely generated, but it was confirmed that the selectivity to the silicon nitride film was lower than that of the silicon oxide film.

On the other hand, in the case of using the silane compound as in Comparative Example 2, the etching rate for the silicon oxide film and the silicon nitride film was decreased as a whole compared to the examples, but silicon-based particles having a size of several tens of micrometers were produced.

According to Comparative Example 3, by using the fluorine-containing compound, the etching rate for the silicon oxide film and the silicon nitride film was generally increased as compared with Comparative Example 2, and the etching rate for the silicon oxide film was increased in particular. In the case of Comparative Example 3, silicon-based particles having a size larger than that of Comparative Example 2 were produced.

On the other hand, according to Examples 1 to 4, it can be confirmed that 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.

On the other hand, according to Example 5, the etching rate for the silicon oxide film was generally increased compared to Examples 1 to 4 by using the fluorine-containing compound, but the etching rate for the silicon nitride film also increased sharply, A high selectivity to a silicon nitride film was obtained.

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 (11)

Inorganic acid aqueous solution; And
At least one salt selected from S-hydrocarbyl thiophene salts and S-hydrocarbyl benzothiophene 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,
The hydrocarbyl is substituted or unsubstituted C ₁ -C ₁₀ alkyl, substituted or unsubstituted C ₆ -C ₁₂ cycloalkyl, substituted or unsubstituted C ₂ -C ₁₀ heteroalkyl, substituted or unsubstituted C ₂ - C ₁₀ alkenyl, substituted or unsubstituted C ₂ -C ₁₀ alkynyl, substituted or unsubstituted C ₁ -C ₁₀ haloalkyl, substituted or unsubstituted C ₁ -C ₁₀ aminoalkyl, or substituted or unsubstituted ring unsubstituted C ₇ -C ₃₀ aralkyl,
Silicon substrate etching solution.
The method of claim 3,
The salt is obtained by substituting a silicon-hydroxyl group (-Si-OH) present on the surface of a silicon substrate or silicon oxide with a silicon-alkoxy group (-Si-OR)
Silicon substrate etching solution.
delete The method according to claim 1,
Wherein the salt in the silicon substrate etching solution contains 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.
8. The method of claim 7,
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.
8. The method of claim 7,
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.
10. The method of claim 9,
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.
10. The method of claim 9,
The fluorine-based anion is selected from fluoride, fluorophosphate, fluoroalkyl-fluorophosphate, fluoroborate, and fluoroalkyl-fluoroborate.
Silicon substrate etching solution.