KR102079041B1 - Etching solution for silicon substrate - Google Patents

Abstract

The present invention relates to a silicon substrate etching solution, and more particularly, to increase the selectivity of the silicon nitride film to the silicon nitride film during the etching of the silicon nitride film, and to prevent the generation of silicon-based particles during etching or during etching after cleaning. It relates to a silicon substrate etching solution.

Description

Silicon Substrate Etch Solution {ETCHING SOLUTION FOR SILICON SUBSTRATE}

The present invention relates to a silicon substrate etching solution, and more particularly, to increase the selectivity of the silicon nitride film to the silicon nitride film during the etching of the silicon nitride film, and to prevent the generation of silicon-based particles during etching or during etching after cleaning. It relates to a silicon substrate etching solution.

Currently, there are several methods of etching silicon nitride and silicon oxide, and dry etching and wet etching are mainly used.

Dry etching is generally a gas-based etching method has the advantage that isotropy is superior to the wet etching method, but the wet etching method is widely used in that the productivity is less expensive and expensive than the wet etching method.

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

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

If only pure phosphoric acid is used to etch the silicon nitride film, the silicon oxide film may be etched not only as the silicon nitride film but also as the silicon oxide film, so that various defects and pattern abnormalities may occur, thereby lowering the etching rate of the silicon oxide film. There is a need.

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

Accordingly, in recent years, silicon additives are used together with phosphoric acid to increase the etching rate of the silicon nitride film and to lower the etching rate of the silicon oxide film.

However, since the silane compound mainly used as a silicone additive has a low solubility in an etching solution containing phosphoric acid, a hydrophilic functional group (eg, a hydroxyl group) is used to increase the solubility of the silane compound in an etching solution. A silane compound in the form of) is used.

As such, when a silane compound having a form in which a hydrophilic functional group is bonded to a silicon atom is used as a silicon additive, proper solubility of the silane compound in an etching solution may be secured, but some problems may occur.

First, when the concentration of the silane compound in the etching solution is increased to increase the selectivity of the silicon nitride film relative to 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. .

In other words, by using a silicon additive, the concentration of silicon in the etching solution is increased to control the etching rate according to the principle of Le Châtlie chemical equilibrium, but when the concentration of silicon becomes higher than an appropriate level, the silicon oxide film In addition, the etching rate for the silicon nitride film is lowered, resulting in a problem of low productivity.

Secondly, with the use of the silane compound as a silicon additive, the increased silicon concentration in the etching solution can act as a source (nucleus or seed) of silicon-based particles, and the silicon-based particles generated during or after cleaning are etched and cleaned substrates. It will act as the biggest cause of poor quality.

For example, a hydrophilic functional group bonded to the silicon atom constituting the silane compound may meet with H ₂ O during etching or washing to be substituted with a hydroxyl group to form a silicon-hydroxy group (-Si-OH), and The hydroxyl group generates a siloxane (-Si-O-Si-) group in which a silicon atom and an oxygen atom are alternately bonded by polymerization to form a random chain structure.

Silane compounds containing siloxane groups are consequently grown and precipitated as silicon-based particles in which the siloxane groups are repeatedly polymerized, and the silicon-based particles remain on the silicon substrate to cause defects of devices implemented on the substrate or to be used in etching or cleaning processes. It can remain in (e.g., filters) and cause equipment failure.

Accordingly, there is a need for the development of a silicon substrate etching solution capable of preventing the generation of silicon-based particles during etching or during etching and at the same time while realizing a high selectivity ratio of the silicon nitride layer to the silicon oxide layer during the etching of the silicon nitride layer.

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

Another object of the present invention is to provide a silicon substrate etching solution capable of preventing generation of silicon-based particles during etching or during cleaning after etching by using reverse phase silica instead of a silane compound as a silicon additive, unlike a conventional silicon substrate etching solution. It is done.

In order to solve the above technical problem, according to an aspect of the present invention, the (A) hydroxy group (-OH) bonded to the silicon atoms of the surface and the terminal of the inorganic acid aqueous solution and silica is (B) saturated or unsaturated hydrocarbon group Or (C) a silicon substrate etching solution comprising reverse phase silica substituted with siloxane groups.

In one embodiment, the reverse phase silica in which the (A) hydroxy group (-OH) bonded to the silicon atom at the surface and the terminal of the silica is substituted with the saturated or unsaturated hydrocarbon group (B) is a repeating unit represented by the following formula (1) It may include.

[Formula 1]

Wherein R ₁ and R ₂ are each independently C ₁ -C ₁₀ alkyl, C ₆ -C ₁₂ cycloalkyl, C ₂ -C ₁₀ heteroalkyl comprising at least one hetero atom, C ₂ -C ₁₀ alkenyl and A hydrocarbon group or a hydroxyl group selected from C ₂ -C ₁₀ alkynyl, at least one of R ₁ and R ₂ is a hydrocarbon group.

At this time, the ratio (A: B) of (A) hydroxy group (-OH) and (B) saturated or unsaturated hydrocarbon group bonded to the surface and terminal silicon atoms of the reversed phase silica is 1: 1 to 1: 9. It is preferable to exist in the range of.

In another embodiment, the reversed phase silica in which the (A) hydroxy group (—OH) bonded to the silicon atom at the surface and the terminal of the silica is substituted with the (C) siloxane group may include a repeating unit represented by the following Chemical Formula 2 Can be.

[Formula 2]

Wherein R ₃ to R ₈ are each independently C ₁ -C ₁₀ alkyl, C ₆ -C ₁₂ cycloalkyl, C ₂ -C ₁₀ heteroalkyl comprising at least one hetero atom, C ₂ -C ₁₀ alkenyl and A hydrocarbon group or a hydroxyl group selected from C ₂ -C ₁₀ alkynyl, at least one of R ₃ to R ₆ is a hydrocarbon group.

At this time, the ratio (A: C) of the (A) hydroxy group (-OH) and the (C) siloxane group bonded to the surface and terminal silicon atoms of the reversed phase silica is in the range of 1: 1 to 1: 9. It is preferable.

In another embodiment, the reversed phase silica may include both a repeating unit represented by Formula 1 below and a repeating unit represented by Formula 2 below.

[Formula 1]

[Formula 2]

Wherein R ₁ and R ₂ are each independently C ₁ -C ₁₀ alkyl, C ₆ -C ₁₂ cycloalkyl, C ₂ -C ₁₀ heteroalkyl comprising at least one hetero atom, C ₂ -C ₁₀ alkenyl and A hydrocarbon group or a hydroxyl group selected from C ₂ -C ₁₀ alkynyl, at least one of R ₁ and R ₂ is a hydrocarbon group, and R ₃ to R ₈ are each independently C ₁ -C ₁₀ alkyl, C _6- C ₁₂ cycloalkyl, C ₂ -C ₁₀ heteroalkyl containing at least one hetero atom, C ₂ -C ₁₀ alkenyl and C ₂ -C ₁₀ alkynyl, a hydrocarbon group or a hydroxyl group selected from R ₃ to At least one of R ₆ is a hydrocarbon group.

In this case, the ratio of (A) hydroxy group (-OH) to (B) saturated or unsaturated hydrocarbon group and (C) siloxane group bonded to the surface and terminal silicon atoms of the reversed phase silica (A: B + C) Is preferably in the range of 1: 1 to 1: 9.

In addition, the silicon substrate etching solution according to the present invention may further include a fluorine-containing compound, wherein the fluorine-containing compound is at least one selected from hydrogen fluoride, ammonium fluoride, ammonium bifluoride and ammonium bifluoride It may be a compound having a form in which an organic cation and a fluorine anion are ionically bonded.

In the silicon substrate etching solution according to the present invention, it is possible to form a protective film on the silicon oxide film by using reverse phase silica as a silicon additive, thereby increasing the selectivity of the silicon nitride film to the silicon oxide film.

In addition, according to the present invention, since the silane compound-based silicone additive is not used unlike the conventional etching solution, it is possible to prevent the generation of silicon-based particles during or after cleaning. As a result, it is possible to prevent defects in the etched silicon substrate caused by silicon-based particles or failure of the etching and cleaning apparatus.

In addition, the silicon substrate etching solution according to the present invention does not need to use a separate dispersant for dispersing the silica, as the silicon additive is used as the reverse phase silica rather than the normal silica, the agglomeration of the silica through the characteristics of the reverse phase silica There is an advantage that can be prevented.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the following embodiments. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, only the present embodiments to make the disclosure of the present invention complete, and common knowledge in the art to which the present invention pertains. It is provided to fully inform the person having the scope of the invention, which is defined only by the scope of the claims.

Wherein the alkyl group R _a (a is an integer from 1 to 6) comprises C ₁ -C ₁₀ alkyl, C ₆ -C ₁₂ cycloalkyl and C ₂ -C ₁₀ heteroalkyl comprising at least one hetero atom, Additionally, where the unsaturated bonds present in any of the adjacent carbon of the alkyl group is C ₂ -C ₁₀ alkenyl or C ₂ -C ₁₀ alkynyl can be imidazol.

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 saturated aliphatic groups having straight chain alkyl, ground alkyl, and the like having a to b carbon atoms. Straight or branched chain alkyl has 10 or less in the main chain thereof (e.g., straight chain, C ₃ -C ₁₀ for grinding of the C ₁ -C _10), preferably four or less, and more preferably no more than three carbon atoms, Has

Specifically, alkyl is methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, i-butyl, t-butyl, pent-1-yl, pent-2-yl, pent-3-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 It may be octyl.

Heterocycloalkyl comprising cycloalkyl or hetero atoms herein will be understood as cyclic structures of alkyl or heteroalkyl, respectively, unless defined otherwise.

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

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 and the like.

In addition, a cycloalkyl or a heterocycloalkyl including a hetero atom may have a form in which cycloalkyl, heterocycloalkyl, aryl or heteroaryl are bonded or covalently linked thereto.

Bonded to the carbon of a hybrid mixed sp- carbon or alkynyl - R _a is an alkenyl or alkynyl imidazol time, alkenyl of sp ² - mixed-carbon, or alkynyl of sp- sp ² hybrid of the alkenyl carbon is bonded directly or Al It may be in the form indirectly bonded by sp ³ -mixed carbon of the alkyl.

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

According to an aspect of the present invention, the reverse phase in which (A) hydroxy group (-OH) bonded to the silicon atom at the surface and the terminal of the inorganic acid aqueous solution and silica is substituted with (B) saturated or unsaturated hydrocarbon group or (C) siloxane group (Reverse phase) A silicon substrate etching solution comprising silica is 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, phosphoric anhydride, pyrophosphoric acid or polyphosphoric acid other than the above-mentioned inorganic acid may be used.

The inorganic acid aqueous solution is a component that maintains the pH of the etching solution to suppress the change in the silane compound of various forms in the etching solution to the silicon-based particles.

In one embodiment, the inorganic acid aqueous solution is preferably included 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 with respect to 100 parts by weight of the silicon substrate etching solution, the etching rate of the silicon nitride film is lowered, so that the silicon nitride film may not be sufficiently etched or the process efficiency of etching the silicon nitride film may be lowered.

On the other hand, when the content of the inorganic acid aqueous solution exceeds 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 oxide film is rapidly etched, so that The selectivity may be lowered, and a defect of the silicon substrate may be caused due to the etching of the silicon oxide layer.

The silicon substrate etching solution according to an embodiment of the present invention includes reverse phase silica as a silicon additive for increasing the selectivity of the silicon nitride film to the silicon oxide film.

Reverse phase silica herein generally refers to silica in the form in which (A) hydroxy group (—OH) bonded to the silicon atom at the surface and terminal of hydrophilic silica is substituted with (B) saturated or unsaturated hydrocarbon group or (C) siloxane group. it means.

According to an embodiment of the present invention, the reversed phase silica in which the (A) hydroxy group (-OH) bonded to the silicon atom at the surface and the terminal of the silica is substituted with the saturated or unsaturated hydrocarbon group (B) is represented by the following Chemical Formula 1 It includes repeating units.

[Formula 1]

Wherein R ₃ to R ₈ are each independently C ₁ -C ₁₀ alkyl, C ₆ -C ₁₂ cycloalkyl, C ₂ -C ₁₀ heteroalkyl comprising at least one hetero atom, C ₂ -C ₁₀ alkenyl and A hydrocarbon group or a hydroxyl group selected from C ₂ -C ₁₀ alkynyl, at least one of R ₃ to R ₆ is a hydrocarbon group.

Reverse phase silica according to the embodiment may include only the repeating unit represented by the formula (1), before or after the repeating unit represented by the formula (1), any silicon atoms located between the repeating unit represented by the formula (1) It may have a form in which a hydroxyl group is bonded to.

For example, the reversed phase silica including the repeating unit represented by Formula 1 may be represented by the following Formula 1-1.

Here, m and m 'means the number of repeating units represented by the formula (1), m and m' may be appropriately selected so that the average diameter of the reverse phase silica is within the range of 5 nm to 100 nm.

Each R is independently C ₁ -C ₁₀ alkyl, C ₆ -C ₁₂ cycloalkyl, C ₂ -C ₁₀ heteroalkyl containing at least one hetero atom, C ₂ -C ₁₀ alkenyl and C ₂ -C ₁₀ alkoxy A hydrocarbon group or a hydroxyl group selected from nil.

[Formula 1-1]

The reversed phase silica according to the embodiment has a form in which a hydroxyl group (-OH) is bonded to some of the silicon atoms existing at arbitrary positions of the surface and the terminal, and thus the polarized silica of the silicon oxide film It is possible to adhere to the surface to form a silica passivation layer.

In this case, as the protective layer is formed on the surface of the silicon oxide film by reversed phase silica, it is possible to prevent the silicon oxide film from being etched by the inorganic acid or the fluorine-containing compound.

In addition, the reversed phase silica according to the embodiment is capable of forming a hydrophobic surface as the hydrocarbon group is bonded to the silicon atoms present at the surface and the terminal, it is possible to impart a certain level of steric hindrance, the aggregation between the reversed phase silica It is possible to prevent.

At this time, the ratio (A: B) of the (A) hydroxy group (-OH) and the (B) saturated or unsaturated hydrocarbon group bonded to the silicon atom at the surface and the terminal of the reverse phase silica is 1: 1 to 1: 9. It is preferable to exist in the range.

When the ratio of (A) hydroxy group (-OH) to (B) saturated or unsaturated hydrocarbon group bonded to the surface and terminal silicon atoms of reverse phase silica is large, the polar interaction between reverse phase silica and silicon oxide film is further increased. However, the likelihood of polar interactions (eg hydrogen bonding) between reverse phase silica may also increase.

In this case, the dispersibility of the reverse phase silica in the etching solution may be reduced due to the aggregation between the reverse phase silica, which may reduce the protective effect on the silicon oxide film. In addition, the agglomeration between the reversed phase silicas may cause the reversed phase silicas to grow into silicon-based particles in micrometer units.

On the other hand, when the ratio of the (A) hydroxy group (-OH) bonded to the silicon atom at the surface and the terminal of the reverse phase silica is extremely small, the polar interaction between the reverse phase silica and the silicon oxide film is reduced to protect the reverse phase silica. Can be difficult to implement.

Further, according to another embodiment of the present invention, the reversed phase silica in which the (A) hydroxy group (-OH) bonded to the silicon atom at the surface and the terminal of the silica is substituted with the (C) siloxane group is represented by the following Chemical Formula 2 It includes repeating units.

[Formula 2]

Wherein R ₃ to R ₈ are each independently C ₁ -C ₁₀ alkyl, C ₆ -C ₁₂ cycloalkyl, C ₂ -C ₁₀ heteroalkyl comprising at least one hetero atom, C ₂ -C ₁₀ alkenyl and A hydrocarbon group or a hydroxyl group selected from C ₂ -C ₁₀ alkynyl.

Reverse phase silica according to the embodiment may include only the repeating unit represented by the formula (2), before or after the repeating unit represented by the formula (2), any silicon atom located between the repeating unit represented by the formula (2) It may have a form in which a hydroxyl group is bonded to.

For example, the reversed phase silica including the repeating unit represented by Formula 2 may be represented by the following Formula 2-1.

Here, n and n 'means the number of repeating units represented by the formula (2), n and n' may be appropriately selected so that the average diameter of the reverse phase silica is within the range of 5 nm to 100 nm.

Each R is independently C ₁ -C ₁₀ alkyl, C ₆ -C ₁₂ cycloalkyl, C ₂ -C ₁₀ heteroalkyl containing at least one hetero atom, C ₂ -C ₁₀ alkenyl and C ₂ -C ₁₀ alkoxy A hydrocarbon group or a hydroxyl group selected from nil, and R 'is a siloxane group.

[Formula 2-1]

Reversed phase silica including the repeating unit represented by the formula (2) has a hydroxyl group (-OH) at some of the silicon atoms present at arbitrary positions of the surface and the terminal, similar to the reversed phase silica including the repeating unit represented by the formula (1) With the bonded form, it is possible to attach to the surface of the silicon oxide film through the polar interaction with the silicon oxide film to form a passivation layer.

At this time, the ratio (A: C) of the (A) hydroxy group (-OH) and the (C) siloxane group bonded to the surface and terminal silicon atoms of the reversed phase silica is in the range of 1: 1 to 1: 9. desirable.

When the ratio of (A) hydroxy group (-OH) to (B) saturated or unsaturated hydrocarbon group bonded to the surface and terminal silicon atoms of reverse phase silica is large, the polar interaction between reverse phase silica and silicon oxide film is further increased. However, the size of the silicon-based particles can also be increased by increasing the likelihood of polar interactions (eg hydrogen bonding) between the reversed phase silicas.

In this case, the dispersibility of reverse phase silica in the etching solution may be reduced due to the aggregation between the reverse phase silica, which may reduce the protective effect on the silicon oxide film. In addition, the agglomeration between the reversed phase silicas may cause the reversed phase silicas to grow into silicon-based particles in micrometer units.

On the other hand, when the ratio of the (A) hydroxy group (-OH) bonded to the silicon atom at the surface and the terminal of the reverse phase silica is extremely small, the polar interaction between the reverse phase silica and the silicon oxide film is reduced to protect the reverse phase silica. Can be difficult to implement.

Further, according to another embodiment of the present invention, it may include both the repeating unit represented by the formula (1) and the repeating unit represented by the formula (2).

For example, as shown in Formula 3 below, the reverse phase silica may have a form in which a repeating unit represented by Formula 1 and a repeating unit represented by Formula 2 are alternately bonded.

[Formula 3]

Here, m and n refer to the number of repeating units represented by the formulas (1) and (2), respectively, and m and n may be appropriately selected such that the average diameter of the reverse phase silica is within the range of 5 nm to 100 nm.

Each R is independently C ₁ -C ₁₀ alkyl, C ₆ -C ₁₂ cycloalkyl, C ₂ -C ₁₀ heteroalkyl containing at least one hetero atom, C ₂ -C ₁₀ alkenyl and C ₂ -C ₁₀ alkoxy A hydrocarbon group or a hydroxyl group selected from nil, and R 'is a siloxane group.

Reversed phase silica including the repeating unit represented by the formula (3), like the reverse phase silica containing the repeating unit represented by the formula (1) or (2), a hydroxyl group (- As OH) has a bonded form, it is possible to form a passivation layer by attaching to the surface of the silicon oxide film through polar interaction with the silicon oxide film.

At this time, the ratio (A: B + C) of (A) hydroxy group (-OH) to (B) saturated or unsaturated hydrocarbon group and (C) siloxane group bonded to the silicon atom at the surface and terminal of reverse phase silica It is preferable to exist in the range of 1: 1 to 1: 9.

The repeating unit represented by the above formulas (1) to (3) is for explaining some examples of the structure of the reversed phase silica according to the present invention, the reverse phase silica used in the silicon substrate etching solution according to the present invention is the surface and terminal of the hydrophilic silica It is to be understood that the (A) hydroxy group (—OH) bonded to the silicon atom of includes various forms of silica substituted with (B) saturated or unsaturated hydrocarbon groups or (C) siloxane groups.

The average diameter of the reverse phase silica used in the silicon substrate etching solution according to the present invention is preferably 5 nm to 100 nm.

If the average diameter of the reversed phase silica is less than 5 nm, the size of the particles may be excessively fine, so that the protective effect on the silicon oxide film may be insignificant. In addition, when reverse phase silica is etched by the fluorine-containing compound by using a fluorine-containing compound and reverse phase silica to increase the etching rate with respect to the silicon substrate (eg, silicon nitride film), the size of the reverse phase silica is It may become finer and lose the protection ability to a silicon oxide film. In addition, when reverse phase silica having an average diameter of less than 5 nm is used together with a fluorine-containing compound, silicon atoms constituting the reverse phase silica may be etched in the form of SiF ₄ to change the concentration of reverse phase silica in the etching solution.

On the other hand, if the average diameter of the reversed phase silica exceeds 100 nm, there is a fear of growing into silicon particles of several to several tens of micrometers due to the interaction between the reversed phase silica.

Accordingly, the reversed-phase silica used in the silicon substrate etching solution according to the present invention may have a mean diameter within the above-described range, so that even if agglomeration occurs due to the interaction between the particles, fluorine- Even if it is etched by the containing compound, it is possible to maintain a size that can sufficiently exhibit a protective effect on the silicon oxide film.

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

Here, the silicon oxide film is a SOD (Spin On Dielectric) film, HDP (High Density Plasma) film, thermal oxide film, thermal phosphate Silicate Glass (BPSG) film, Phospho Silicate Glass (PSG) film, etc. , BSG (Boro Silicate Glass) film, PSZ (Polysilazane) film, FSG (Fluorinated Silicate Glass) film, LP-TEOS (Low Pressure Tetra Ethyl Ortho Silicate) film, PETEOS (Plasma Enhanced Tetra Ethyl Ortho Silicate) film, HTO (High) Temperature Oxide (MTO) 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-Plasma film Enhanced oxide) or O ₃ -TEOS (O ₃ -Tetra Ethyl Ortho Silicate) and the like.

In general, since a plurality of silicon particles or atoms constituting the silicon oxide film are present in a state substituted with a hydroxyl group (-OH), there is a fear of growing into silicon-based particles during the etching or after washing with water during washing.

Therefore, in order to reduce the rate at which the silicon oxide film is etched by the inorganic acid during the etching, and to reduce or suppress the generation of the silicon-based particles during the cleaning or the post-etch cleaning, the silicon substrate etching solution according to the present invention uses silicon by using reverse phase silica. It is possible to reduce the etching rate of the silicon oxide film by forming a protective film on the surface of the substrate, particularly the silicon oxide film.

In addition, it is possible to reduce the growth of the silicon particles bonded to the hydroxyl group in the form of silicic acid during etching, and further to prevent the growth and precipitation of silicon particles of several to several tens of micrometers during cleaning after etching. .

That is, the silicon substrate etching solution according to the present invention solves the problem caused by using the silicon additive in that the reverse phase silica is used instead of the silane compound which may cause the decrease in the etching rate and the generation of silicon-based particles to the silicon nitride film. can do.

In addition, since the silicon substrate etching solution according to the present invention has a relatively complex structure in the etching solution, and there is no silane compound that is difficult to separate, it is possible to easily separate and recycle the pure inorganic acid from the etching solution used for etching. There is this.

The above-mentioned reverse phase silica is preferably present in 50 to 20,000 ppm in the silicon substrate etching solution, more preferably the reverse phase silica is included in the content of 300 to 5,000 ppm.

When the reverse phase silica is present in the silicon substrate etching solution less than 50 ppm, the protective effect of the silicon oxide film by the reverse phase silica may be insufficient. On the other hand, when the content of reverse phase silica in the silicon substrate etching solution exceeds 20,000 ppm, the possibility of polar interaction (eg, hydrogen bonding) between reverse phase silica may increase. In this case, the dispersibility of the reverse phase silica in the etching solution may be reduced due to the aggregation between the reverse phase silica, which may reduce the protective effect on the silicon oxide film. In addition, the agglomeration between the reversed phase silicas may cause the reversed phase silicas to grow into silicon-based particles in micrometer units.

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 substrate (particularly, silicon nitride film). When the silicon substrate etching solution according to the present invention is used, the silicon oxide film may be protected by reverse phase silica, and thus, the etching rate of the silicon oxide film may be prevented from increasing by the fluorine-containing compound.

Fluorine-containing compounds herein refer to all types of compounds capable of dissociating fluorine ions.

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

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 the alkylammonium and the fluorine-based anion are ionically bound. Here, the alkylammonium is ammonium having at least one alkyl group and may have up to four alkyl groups. Definitions for alkyl groups have been described above.

In another example, the fluorine-containing compound is alkylpyrrolium, alkylimidazolium, alkylpyrazolium, alkyloxazolium, alkylthiazolium, alkylpyridinium, alkylpyrimidinium, alkylpyridazinium, alkylpyra Organic cations selected from genium, alkylpyrrolidinium, alkylphosphonium, alkylmorpholinium and alkylpiperidinium and fluorophosphates, fluoroalkyl-fluorophosphates, fluoroborates and fluoroalkyl-fluoro The fluorine-based anion selected from roborate may be an ionic liquid in ionic bond form.

Compared to hydrogen fluoride or ammonium fluoride, which are generally used as fluorine-containing compounds in silicon substrate etching solutions, fluorine-containing compounds, which have a high boiling point and decomposition temperature, are decomposed during the etching process performed at high temperatures. As a result, there is little concern that the composition of the etching solution may be changed.

The following presents specific embodiments of the present invention. However, the embodiments described below are merely for illustrating or explaining the present invention in detail, and thus the present invention is not limited thereto.

Experimental Example  One

An etch solution was prepared by combining the additives in an amount of 750 g of an aqueous 85% phosphoric acid solution in Table 1 below.

division Silane compound (ppm) Silica (ppm) Fluorine-containing compound (ppm) Example 1 - 500 - Example 2 - 500 1,000 Comparative Example 1 1,000 - - Comparative Example 2 1,000 - 1,500

Here, the silane compounds used in Comparative Examples 1 and 2 are 3-aminopropylsilanetriol, and the fluorine-containing compounds used in Examples 2 and 2 are hydrofluoric acid (HF).

The silicas used in Examples 1 and 2 are reverse phase silicas in which (A) hydroxy group (—OH) bonded to the silicon atom at the surface and terminal of the silica is substituted with (B) methyl group, and the surface of reverse phase silica and The ratio (A: B) of the (A) hydroxy group (-OH) and the (B) methyl group bonded to the terminal silicon atom is 1: 4.

After the etching solution was heated to 165 ° C., the silicon substrate including the ALD oxide layer and the silicon nitride layer was immersed for 3 minutes and etched. The thicknesses of the silicon oxide film and the silicon nitride film before and after the etching were measured using an Ellipsomitri (Nano-View, SE MG-1000; Ellipsometery), and the measurement results are average values of five measurement results. The etching rate is a value calculated by dividing the thickness difference between the silicon oxide film and the silicon nitride film before and after etching by the etching time (3 minutes).

After the etching was completed, the silicon substrate was rinsed with distilled water at 165 ℃ for 10 seconds. Subsequently, the distilled water used for the rinse was analyzed with a particle size analyzer to determine the average diameter of the silicon particles present in the distilled water.

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

division Silicon particle
Average diameter (μm) Silicon oxide
Etch Speed (Å / min) Silicon nitride film
Etch Speed (Å / min) Example 1 <0.01 1.16 63.44 Example 2 <0.01 2.31 165.72 Comparative Example 1 11.2 4.72 60.21 Comparative Example 2 9.8 16.45 158.96

When the silane compound was used together with the inorganic acid as in Comparative Example 1, although the etching rates of the silicon oxide film and the silicon nitride film were decreased, it was confirmed that silicon particles having a size of about 10 micrometers were formed.

According to Comparative Example 2, the etching rate of the silicon oxide film and the silicon nitride film as compared with Comparative Example 1 overall increased. In particular, it can be seen that the etching rate of the silicon oxide film is rapidly increased, and that the silicon-based particles are also generated.

On the other hand, according to Example 1 and Example 2, the silicon particles are present in a very fine size or hardly generated, it can be seen that the selectivity for the silicon nitride film compared to the silicon oxide film is also improved.

Experimental Example  2

An etch solution was prepared by combining the additives in 750 g of an aqueous 85% phosphoric acid solution in the amounts shown in Table 3 below.

division Silica (ppm) Fluorine-containing compound (ppm) Example 3 500 - Example 4 500 1,000 Comparative Example 3 500 - Comparative Example 4 500 -

The silicas used in Examples 3 and 4 are reverse phase silicas in which (A) hydroxy group (—OH) bonded to the silicon atom at the surface and terminal of the silica is substituted with (C) trimethylsiloxane group, The ratio (A: B) of the (A) hydroxy group (-OH) and the (C) methyl group bonded to the surface and terminal silicon atoms is 1: 8.

The silica used in Comparative Example 3 is fumed silica (Aldrich 805890), and the silica used in Comparative Example 4 is colloidal silica (Aldrich 420875).

After the etching solution was heated to 165 ° C., the silicon substrate including the ALD oxide layer and the silicon nitride layer was immersed for 3 minutes and etched. The thicknesses of the silicon oxide film and the silicon nitride film before and after the etching were measured using an Ellipsomitri (Nano-View, SE MG-1000; Ellipsometery), and the measurement results are average values of five measurement results. The etching rate is a value calculated by dividing the thickness difference between the silicon oxide film and the silicon nitride film before and after etching by the etching time (3 minutes).

After the etching was completed, the silicon substrate was rinsed with distilled water at 165 ℃ for 10 seconds. Subsequently, the distilled water used for the rinse was analyzed with a particle size analyzer to determine the average diameter of the silicon particles present in the distilled water.

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

division Silicon particle
Average diameter (μm) Silicon oxide
Etch Speed (Å / min) Silicon nitride film
Etch Speed (Å / min) Example 3 <0.01 1.16 63.44 Example 4 <0.01 2.31 165.72 Comparative Example 3 31.7 10.38 63.97 Comparative Example 4 25.9 13.99 62.65

As shown in Table 4, in contrast to Examples 3 and 4, even if silica was used as the silicon additive, Comparative Example 3 and Comparative Example 4 using fumed silica or colloidal silica as normal silica instead of reverse phase silica In this case, the selectivity of the silicon nitride film compared to the silicon oxide film is low, and it can be seen that after etching, silicon particles of several tens of micrometers are generated.

Experimental Example  3

750 g of an aqueous 85% phosphoric acid solution was combined with silica in the amount shown in Table 5 to prepare an etching solution.

division Silica (ppm) Example 5 500 Example 6 500 Comparative Example 5 500 Comparative Example 6 500

The silica used in Example 5 is reverse phase silica in which (A) hydroxy group (-OH) bonded to the silicon atom at the surface and terminal of the silica is substituted with (B) ethyl group, and the silicon atom at the surface and terminal of reverse phase silica The ratio (A: B) of (A) hydroxy group (-OH) and (B) ethyl group bonded to is 1: 4.

The silica used in Example 6 is reverse phase silica in which (A) hydroxy group (-OH) bonded to the silicon atom at the surface and terminal of silica is substituted with (C) triethylsiloxane group, The ratio (A: B) of (A) hydroxy group (-OH) to (C) triethylsiloxane group bonded to a silicon atom is 1: 4.

The (A) hydroxy group (-OH) bonded to the surface and terminal silicon atoms of the silica used in Comparative Example 5 is reverse phase silica substituted with the (B) ethyl group, and bonded to the surface and terminal silicon atoms of the reverse phase silica. The ratio (A: B) of the (A) hydroxy group (-OH) and the (B) ethyl group is 3: 2.

Silica used in Comparative Example 6 is a reversed phase silica in which all of the hydroxyl groups (-OH) bonded to the silicon atoms at the surface and the terminal of the silica are substituted with triethylsiloxane groups, and (A) hydroxyl groups (-OH) and ( C) The ratio of triethylsiloxane groups (A: B) is 3: 2.

After the etching solution was heated to 165 ° C., the silicon substrate including the ALD oxide layer and the silicon nitride layer was immersed for 3 minutes and etched. The thicknesses of the silicon oxide film and the silicon nitride film before and after the etching were measured using an Ellipsomitri (Nano-View, SE MG-1000; Ellipsometery), and the measurement results are average values of five measurement results. The etching rate is a value calculated by dividing the thickness difference between the silicon oxide film and the silicon nitride film before and after etching by the etching time (3 minutes).

After the etching was completed, the silicon substrate was rinsed with distilled water at 165 ℃ for 10 seconds. Subsequently, the distilled water used for the rinse was analyzed with a particle size analyzer to determine the average diameter of the silicon particles present in the distilled water.

The measured etch rate and average diameter of the silicon-based particles in the etch solution are listed in Table 6 below.

division Silicon particle
Average diameter (μm) Silicon oxide
Etch Speed (Å / min) Silicon nitride film
Etch Speed (Å / min) Example 5 <0.01 13.11 61.01 Example 6 <0.01 11.59 62.05 Comparative Example 5 3. 78 8. 19 59.98 Comparative Example 6 4. 97 5. 97 62.05

As shown in Table 6, although the reverse phase silica is used as the silicone additive, the ratio of the (A) hydroxy group (-OH) bonded to the silicon atom at the surface and the terminal of the reverse phase silica is different from that of Examples 5 and 6 When the functional group is more than the ratio of (B) ethyl group or (C) triethylsiloxane group, the protective effect on the silicon oxide film, that is, the selectivity of the silicon nitride film to the silicon oxide film may be slightly increased, but the silicon-based unit of several micrometers is used. You can see the particles being created.

As mentioned above, although an embodiment of the present invention has been described, those of ordinary skill in the art may add, change, delete or add elements within the scope not departing from the spirit of the present invention described in the claims. The present invention may be modified and changed in various ways, etc., which will also be included within the scope of the present invention.

Claims (14)

Inorganic acid aqueous solution; And
Reverse phase silica in which a portion of the (A) hydroxy group (—OH) bonded to the silicon atom at the surface and terminal of the silica is substituted with (B) a saturated or unsaturated hydrocarbon group or (C) siloxane group;
Containing,
Silicon substrate etching solution.
The method of claim 1,
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 anhydride, pyrophosphoric acid and polyphosphoric acid,
Silicon substrate etching solution.
The method of claim 1,
Reverse phase silica in which a part of the (A) hydroxy group (—OH) bonded to the silicon atom at the surface and the terminal of the silica is substituted with a saturated or unsaturated hydrocarbon group (B) comprises a repeating unit represented by the following formula
Silicon Substrate Etch Solution:
[Formula 1]

Wherein R ₁ and R ₂ are each independently C ₁ -C ₁₀ alkyl, C ₆ -C ₁₂ cycloalkyl, C ₂ -C ₁₀ heteroalkyl comprising at least one hetero atom, C ₂ -C ₁₀ alkenyl and A hydrocarbon group or a hydroxyl group selected from C ₂ -C ₁₀ alkynyl,
At least one of R ₁ and R ₂ is a hydrocarbon group.
The method of claim 3,
The ratio (A: B) of (A) hydroxy group (-OH) and (B) saturated or unsaturated hydrocarbon group bonded to the surface and terminal silicon atoms of the reversed phase silica is 1: 1 to 1: 9,
Silicon substrate etching solution.
The method of claim 1,
Reverse phase silica in which a part of the (A) hydroxy group (-OH) bonded to the silicon atom at the surface and the terminal of the silica is substituted with the (C) siloxane group includes a repeating unit represented by the following formula (2),
Silicon Substrate Etch Solution:
[Formula 2]

Wherein R ₃ to R ₈ are each independently C ₁ -C ₁₀ alkyl, C ₆ -C ₁₂ cycloalkyl, C ₂ -C ₁₀ heteroalkyl comprising at least one hetero atom, C ₂ -C ₁₀ alkenyl and A hydrocarbon group or a hydroxyl group selected from C ₂ -C ₁₀ alkynyl,
At least one of R ₃ to R ₈ is a hydrocarbon group.
The method of claim 5,
The ratio (A: C) of (A) hydroxy group (-OH) and (C) siloxane group bonded to the surface and terminal silicon atoms of the reversed phase silica is 1: 1 to 1: 9,
Silicon substrate etching solution.
The method of claim 1,
The reversed phase silica includes both a repeating unit represented by the following Formula 1 and a repeating unit represented by the following Formula 2,
Silicon Substrate Etch Solution:
[Formula 1]

[Formula 2]

here,
R ₁ and R ₂ are each independently C ₁ -C ₁₀ alkyl, C ₆ -C ₁₂ cycloalkyl, C ₂ -C ₁₀ heteroalkyl containing at least one hetero atom, C ₂ -C ₁₀ alkenyl and C ₂ A hydrocarbon group or a hydroxyl group selected from -C ₁₀ alkynyl, at least one of R ₁ and R ₂ is a hydrocarbon group,
R ₃ to R ₈ are each independently C ₁ -C ₁₀ alkyl, C ₆ -C ₁₂ cycloalkyl, C ₂ -C ₁₀ heteroalkyl containing at least one hetero atom, C ₂ -C ₁₀ alkenyl and C ₂ -C ₁₀ is a hydrocarbon group or a hydroxyl group selected from alkynyl,
At least one of R ₃ to R ₈ is a hydrocarbon group.
The method of claim 7, wherein
The ratio (A: B + C) of (A) hydroxy group (-OH) to (B) saturated or unsaturated hydrocarbon group and (C) siloxane group bonded to the surface and terminal silicon atoms of the reversed phase silica is 1: 1 to 1: 9,
Silicon substrate etching solution.
The method of claim 1,
The average diameter of the reversed phase silica is 5 nm to 100 nm,
Silicon substrate etching solution.
The method of claim 1,
Further comprising a fluorine-containing compound,
Silicon substrate etching solution.
The method of claim 10,
The fluorine-containing compound is at least one selected from hydrogen fluoride, ammonium fluoride, ammonium bifluoride and ammonium bifluoride,
Silicon substrate etching solution.
The method of claim 10,
The fluorine-containing compound is a compound having a form in which an organic cation and a fluorine anion are ion-bonded,
Silicon substrate etching solution.
The method of claim 12,
The organic cation is alkylammonium, alkylpyrrolium, alkylimidazolium, alkylpyrazolium, alkyloxazolium, alkylthiazolium, alkylpyridinium, alkylpyrimidinium, alkylpyridazinium, alkylpyrazinium, alkyl Selected from pyrrolidinium, alkylphosphonium, alkylmorpholinium and alkylpiperidinium,
Silicon substrate etching solution.
The method of claim 12,
The fluorine anion is selected from fluoride, fluorophosphate, fluoroalkyl-fluorophosphate, fluoroborate and fluoroalkyl-fluoroborate,
Silicon substrate etching solution.