KR102284210B1 - Etching solution for silicon substrate - Google Patents

Abstract

The present invention relates to a silicon substrate etching solution, and more particularly, by giving a passivation effect to the silicon oxide film when the silicon nitride film is etched to increase the selectivity for the silicon nitride film compared to the silicon oxide film, and at the same time, a separate silicon additive in the etching solution The present invention relates to a silicon substrate etching solution capable of preventing silicon-based particles from being generated as they are not used.

Description

Silicon substrate etching solution {ETCHING SOLUTION FOR SILICON SUBSTRATE}

The present invention relates to a silicon substrate etching solution, and more particularly, by giving a passivation effect to the silicon oxide film when the silicon nitride film is etched to increase the selectivity for the silicon nitride film compared to the silicon oxide film, and at the same time, a separate silicon additive in the etching solution The present invention relates to a silicon substrate etching solution capable of preventing silicon-based particles from being generated as they are not used.

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

The dry etching method is generally an etching method using a gas, and has the advantage that the isotropy is superior to the wet etching method.

In general, as a wet etching method, a method using phosphoric acid as an etching solution is well known, and etching of a silicon nitride layer 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

If only pure phosphoric acid is used for etching the silicon nitride film, as the device becomes miniaturized, not only the silicon nitride film but also the silicon oxide film may be etched, which may cause problems such as various defects and pattern abnormalities. There is a need.

On the other hand, there have been attempts to use a compound containing fluorine as an additive to further increase the etching rate of the silicon nitride film, but fluorine has a disadvantage in that it increases the etching rate of the silicon oxide film.

Accordingly, in recent years, a silicon additive is used together with phosphoric acid to increase the etching rate of the silicon nitride layer and decrease the etching rate of the silicon oxide layer.

However, since the silane compound mainly used as a silicone additive basically has low solubility in an etching solution containing phosphoric acid, a hydrophilic functional group (for example, a hydroxyl group) on the silicon atom to increase the solubility of the silane compound in the etching solution ) in the form of a combined silane compound is used.

When a silane compound in which a hydrophilic functional group is bonded to a silicon atom is used as a silicon additive as described above, proper solubility of the silane compound in an etching solution can be secured, but several problems occur.

First, if the concentration of the silane compound in the etching solution is increased to increase the selectivity of the silicon nitride layer compared to the silicon oxide layer, the etching rate of the silicon nitride layer may be lowered according to the increased silicon concentration in the etching solution. .

That is, as the silicon additive is used, the concentration of silicon in the etching solution is increased to control the etching rate according to the principle of Le Chatelier chemical equilibrium. In addition, the etching rate of the silicon nitride film is also lowered, resulting in a problem of reduced productivity.

Second, by using a silane compound as a silicon additive, the silicon-based concentration in the etching solution may act as a source (nucleus or seed) of silicon-based particles, and the silicon-based particles generated during etching or post-etch cleaning are the etched and cleaned substrates. It is the biggest cause of the failure of

For example, a hydrophilic functional group bonded to a silicon atom may be _{substituted with a hydroxyl group by meeting with H 2} O during etching or washing to form a silicon-hydroxy group (-Si-OH), and the silicon-hydroxy group may be polymerized. By this, a siloxane (-Si-O-Si-) group in which a silicon atom and an oxygen atom are alternately combined to form a random chain structure is generated.

As a result, the silane compound containing the siloxane group is grown and precipitated as silicon-based particles in which the siloxane group is repeatedly polymerized, and the silicon-based particles remain on the silicon substrate to cause defects in devices implemented on the substrate or equipment used in the etching or cleaning process. It can remain in the filter (eg filter) and cause equipment failure.

Therefore, it is necessary to develop a silicon substrate etching solution capable of realizing a high selectivity for a silicon nitride film compared to a silicon oxide film during etching of the silicon nitride film and preventing the generation of silicon-based 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 for 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 capable of preventing the etching rate from being lowered due to the use of the silicon additive by not using the silicon additive unlike the conventional silicon substrate etching solution.

In addition, the present invention provides a silicon substrate etching solution capable of preventing the generation of silicon-based particles during etching or cleaning after etching according to the use of a silicon additive by not using a silicon additive unlike a conventional silicon substrate etching solution. aim to

In order to solve the above-described technical problem, according to an aspect of the present invention, a silicon substrate etching solution including an inorganic acid aqueous solution and a silicon oxide layer etch inhibitor may be provided.

Here, the silicon oxide layer etch inhibitor may be represented by the following formula (1).

[Formula 1]

here,

R ₁ and R ₂ are independently of each other 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 substituted 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 C ₇ -C ₃₀ aralkyl, and R ₃ and R ₄ are each independently hydrogen or methyl.

In this case, preferably R ₁ and R ₂ are each independently a branched alkyl, heteroalkyl, alkenyl, alkynyl, haloalkyl or aminoalkyl having 3 or more carbon atoms, and at least one of _{R 3} and R ₄ is methyl.

At this time, the silicon oxide film etch inhibitor is a silicon-hydroxy group (-Si-OH) present on the surface of the silicon substrate or silicon oxide film, silicon-alkylcarboxyl group (-Si-CR ₃ R ₄ -CO ₂ H) or silicon By substituting with an -alkyl ester group (-Si-CR ₃ R ₄ -CO ₂ R ₁ or -SiCR ₃ R ₄ -CO ₂ R ₂ ), it is possible to form a passivation layer on the silicon oxide film.

Accordingly, even if a separate silicon additive such as a silane compound is not used, it is possible to prevent the silicon oxide layer from being etched and the etching selectivity for the silicon nitride layer compared to the silicon oxide layer from being lowered.

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, or an organic type. It may be a compound in which a cation and a fluorine-based anion are ionically bonded.

Since the silicon substrate etching solution according to the present invention uses a silicon oxide film etch inhibitor, a protective film is formed on the silicon oxide film without using a silicon additive, thereby increasing the selectivity for the silicon nitride film compared to the silicon oxide film.

In addition, according to the present invention, there is an advantage that the etching rate of the silicon substrate does not decrease due to the use of the silicon additive by not using the silicon additive unlike the conventional etching solution.

In addition, according to the present invention, since silicon additives are not used, unlike conventional etching solutions, silicon-based particles are generated during etching or during cleaning after etching, thereby preventing the failure of the silicon substrate or the failure of the etching and cleaning apparatus. .

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

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

According to one aspect of the present invention, a silicon substrate etching solution including an inorganic acid aqueous solution and a silicon oxide layer etch inhibitor 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, 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 and inhibits the change of various types of silane compounds present in the etching solution into silicon-based particles.

In one embodiment, the inorganic acid aqueous solution is preferably included 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 layer is lowered, so that the silicon nitride layer is not sufficiently etched or the process efficiency of the etching of the silicon nitride layer may be reduced.

On the other hand, when the content of the inorganic acid aqueous solution exceeds 90 parts by weight with respect to 100 parts by weight of the etching solution for the silicon substrate, the etching rate of the silicon nitride film is excessively increased, and the silicon oxide film is etched quickly. The selectivity may be lowered, and the silicon substrate may be defective due to the etching of the silicon oxide layer.

The silicon substrate etching solution according to an embodiment of the present invention includes a silicon oxide layer etch inhibitor represented by the following Chemical Formula 1 in order to increase the selectivity for the silicon nitride layer over the silicon oxide layer.

[Formula 1]

As shown in Formula 1 above, the silicon oxide film etch inhibitor herein is defined as a compound in which an ester group is bonded to both sides around a methylene carbon, and the alkyl group bonded to the oxygen atom of the two ester groups may be the same or different from each other. can Also, methylene carbon may be bonded to hydrogen or methyl.

More specifically, R ₁ and R ₂ are independently of each other 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 C ₇ -C ₃₀ aralkyl, and R ₃ and R ₄ are independently of each other hydrogen or methyl.

Wherein, R ₁ or if R ₂ is substituted with a functional group, any carbon of R ₁ or R ₂ is substituted with alkyl, cycloalkyl, heteroalkyl, alkenyl, alkynyl, haloalkyl, aminoalkyl, halogen or hydroxy In addition to the functional groups described above, it is also possible to be substituted with various substituents within a range that does not change the properties of the silicon oxide film etch inhibitor.

A C _a -C _b functional group herein refers to a functional group having a to b carbon atoms. For example, C _a -C _b alkyl refers to saturated aliphatic groups having a to b carbon atoms, including straight chain alkyl and branched alkyl and the like. A straight chain or branched alkyl has 10 or fewer (eg C ₁ -C ₁₀ straight chain, C ₃ -C ₁₀ comminuted), preferably 4 or less, more preferably 3 or less carbon atoms in its backbone. have

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 - May be octyl.

Hydrocarbon cycloalkyl or heterocycloalkyl containing heteroatoms herein shall be understood as a cyclic structure 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- Morpholinyl, 3-morpholinyl, tetrahydrofuran-2-yl, tetrahydrofuran-3-yl, tetrahydrothien-2-yl, tetrahydrothien-3-yl, 1-piperazinyl and 2 - Piperazinil, etc.

In addition, cycloalkyl or heterocycloalkyl containing a hetero atom may have a form in which cycloalkyl, heterocycloalkyl, aryl or heteroaryl is conjugated or covalently linked thereto.

Alkenyl or alkynyl is a functional group in which an unsaturated bond exists between any two adjacent carbons, and when R is alkenyl or alkynyl, the sp ² -hybridized carbon of alkenyl or sp-hybridized carbon of alkynyl is directly bonded or ^{indirectly bonded by sp 2 -hybrid carbon of alkenyl or sp 3} -hybrid carbon of alkyl bonded to sp-hybrid carbon of alkynyl.

In addition, haloalkyl means an alkyl substituted with the aforementioned halogen. _{For example, halomethyl is methyl (-CH 2} X, -CHX _{2 ) in} which at least one of the methyl's hydrogens is replaced by a halogen. or -CX ₃ ). Aminoalkyl means alkyl substituted with amino.

As used herein, aralkyl is a functional group in which aryl is substituted at the carbon of alkyl, and is a generic term for _{-(CH 2} ) _{n Ar.} Examples of aralkyl include benzyl (—CH ₂ C ₆ H ₅ ) or phenethyl (—CH ₂ CH ₂ C ₆ H ₅ ) and the like.

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

As used herein, the silicon oxide film etch inhibitor is a silicon-hydroxy group (-Si-OH) present on the surface of a silicon substrate or a silicon oxide film, a silicon-alkylcarboxyl group (-Si-CR ₃ R ₄ -CO ₂ H) or It serves to substitute a silicon-alkyl ester group (-Si-CR ₃ R ₄ -CO ₂ R ₁ or -SiCR ₃ R ₄ -CO ₂ R ₂ ), through which a passivation layer is formed on the silicon oxide film. do.

The silicon-hydroxy group (-Si-OH) present on the surface of the silicon substrate or silicon oxide film by the silicon oxide film etch inhibitor used herein is a silicon-alkylcarboxyl group (-Si-CR ₃ R ₄ -CO ₂ H) The passivation reaction mechanism in which a protective film is formed on the silicon oxide film by converting to can be summarized in Reaction Schemes 1 and 2 below.

[Scheme 1]

[Scheme 2]

Here, Scheme 1 starts from a saponification reaction in which two ester groups present on both sides of the methylene carbon of the silicon oxide layer etch inhibitor are converted to carboxyl groups under a high temperature aqueous inorganic acid solution. Subsequently, decarboxylation occurs in which the carboxyl group at one end is released in the form of carbon dioxide under high-temperature conditions, thereby obtaining a carboxylic acid having a (-)-charge at the α-carbon position.

Subsequently, Scheme 2 shows that a silicon-hydroxy group (-Si-OH) present on the surface of a silicon substrate or a silicon oxide film is converted into a ^{silicon-oxonium group (-Si-O +} H _{2 ) under a high-temperature aqueous inorganic acid solution.} It starts from the reaction (protonation). _{Thereafter, a protective layer in which an alkylcarboxyl group (-Si-CR 3} R ₄ -CO ₂ H) is bonded to silicon may be formed by a substitution reaction with a (-)-charged carboxylic acid generated from Scheme 1.

Since the alkylcarboxyl group bonded to the silicon atom is stable under a high temperature aqueous solution of an inorganic acid unlike the hydroxyl group, it is possible to prevent the silicon oxide film from being etched by the inorganic acid.

Accordingly, even if a separate silicon additive such as a silane compound is not used, it is possible to prevent the silicon oxide layer from being etched by phosphoric acid or a fluorine-containing compound, thereby preventing a decrease in the etch selectivity for the silicon nitride layer compared to the silicon oxide layer.

In addition, in some cases, when the saponification reaction in Scheme 1 occurs partially, a (-)-charged ester including R1 or R2 may be formed. When this ester reacts with a silicone-hydroxy group, silicone-alkyl A protective layer to which an ester group (-Si-CR ₃ R ₄ -CO ₂ R ₁ or -SiCR ₃ R ₄ -CO ₂ R ₂ ) is bonded may be formed.

On the other hand, in the case of the (-)-charged carboxylic acid generated from Scheme 1, instead of reacting with a silicon-hydroxy group, a nucleophilic acyl substitution reaction occurs with the carbonyl carbon of the silicon oxide layer etch inhibitor represented by Formula 1 or R ₃ or When R ₄ is hydrogen, there is a risk of causing an acid-base reaction with hydrogen.

Accordingly, it is preferred that R ₁ and R ₂ are at least cycloalkyl or aralkyl, or branched alkyl, heteroalkyl, alkenyl, alkynyl, haloalkyl or aminoalkyl having 3 or more carbon atoms.

Thus, by steric hindrance effect by the R ₁ or R ₂ generated from Scheme 1 (-) - charged carboxylic acid is R ₁ or R ₂ is to reduce the possibility of attacking the carbonyl carbon of the ester group bonded as a group can

In addition, _{at least one of R 3} or R ₄ may have a methyl group, thereby increasing the electron density of the (-)-charge of the (-)-charged carboxylic acid through an electron donating inductive effect, thus Accordingly, the rate of substitution reaction of the silicone-hydroxy group by the (-)-charged carboxylic acid can be improved.

If _{at least one of R 3} or R ₄ is a bulky functional group than a methyl group, there is a fear that access of the (-)-charged carboxylic acid to a silicon atom for a substitution reaction may be inhibited, so R ₃ or When _{at least one of R 4} is an alkyl group, it is preferably a methyl group having one carbon number.

The silicon substrate to be etched by the silicon substrate etching solution according to the present invention _{preferably includes at least a silicon oxide film (SiO x} ), and includes a silicon oxide film and a silicon nitride film (Si _x N _y , SI _x O _y N _z ) at the same time. can also. In the case of a silicon substrate including a silicon oxide layer and a silicon nitride layer at the same time, the silicon oxide layer and the silicon nitride layer 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, BPSG (Borophosphate Silicate Glass) film, PSG (Phospho Silicate Glass) film depending on the use and type of material, 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 Pressure Tetra Ethyl Ortho Silicate) film Temperature Oxide) film, MTO (Medium Temperature Oxide) film, USG (Undoped Silicate Glass) film, SOG (Spin On Glass) film, APL (Advanced Planarization Layer) film, ALD (Atomic Layer Deposition) film, PE-Oxide film (Plasma) film Enhanced oxide) or O ₃ -TEOS (O ₃ -Tetra Ethyl Ortho Silicate) and the like.

In general, since a large number of silicon particles or atoms constituting the silicon oxide film exist in a state substituted with a hydroxyl group (-OH), there is a risk of growing into silicon-based particles by meeting with water during etching or during cleaning after etching.

Therefore, in order to reduce the rate at which the silicon oxide film is etched by the inorganic acid during etching and further reduce or suppress the generation of silicon-based particles during etching or cleaning after etching, the etching solution according to the present invention uses a silicon oxide film etch inhibitor. A hydroxyl group bonded to silicon present on the surface of the substrate or silicon oxide film is an alkylcarboxyl group (-CR ₃ R ₄ -CO ₂ H) or an alkylester group (-CR ₃ R ₄ -CO ₂ R ₁ or -CR ₃ R _{By substituting with 4-} CO ₂ R ₂ ), a protective film is formed on the surface of the silicon substrate, particularly, the silicon oxide film.

A silicon-hydroxy group (-Si-OH) present on the surface of the silicon substrate or silicon oxide film may be alkylcarboxylated or alkylesterified, so that further hydroxylation may be limited. Accordingly, it is possible to reduce the growth of silicon particles having a hydroxyl group in the form of silicic acid during etching or during cleaning after etching, and furthermore, it is possible to prevent the silicon particles from being separated from the silicon substrate to grow and precipitate as silicon-based particles. can

In addition, as described above, it is possible to form a protective film on the surface of the silicon oxide film by alkylcarboxylation or alkyl ester of a silicon-hydroxy group (-Si-OH), so reducing the etching rate of the silicon oxide film by an inorganic acid It is possible, and it is possible to prevent a decrease in the etch selectivity of the silicon nitride layer compared to the silicon oxide layer even if the silicon additive in the etching solution is not mixed and used.

That is, the etching solution according to the present invention uses a silicon oxide film etch inhibitor instead of a silicon additive that may cause a decrease in the etching rate for the silicon nitride film and generation of silicon-based particles, thereby solving the problem caused by using a silicon additive. can do.

In addition, since the etching solution according to the present invention does not contain a silicon additive that is difficult to separate due to a relatively complex structure in the etching solution, it is possible to easily separate and recycle the pure inorganic acid from the etching solution used for etching. There is an advantage.

The above-described silicon oxide layer etch inhibitor is preferably present in an amount of 200 to 50,000 ppm in the silicon substrate etching solution.

When the amount of the silicon oxide layer etch inhibitor in the silicon substrate etching solution is less than 200 ppm, the protective effect on the silicon oxide layer is insufficient, so it may be difficult to express the effect of increasing the selectivity for the silicon nitride layer compared to the silicon oxide layer. On the other hand, when the amount of the silicon oxide layer etch inhibitor in the silicon substrate etching solution exceeds 50,000 ppm, the etching rate of the silicon nitride layer is remarkably reduced, so it may be difficult to increase the selectivity of the silicon nitride layer compared to the silicon oxide layer.

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 layer. When the etching solution according to the present invention is used, the silicon oxide layer may be protected by the silicon oxide layer etch inhibitor, and thus the etching rate of the silicon oxide layer may be prevented from increasing by the fluorine-containing compound.

A 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 bifluoride and ammonium bifluoride.

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

For example, the fluorine-containing compound may be a compound in which alkylammonium and a fluorine-based anion are ionically bonded. Here, the 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 an alkylpyrrolium, alkylimidazolium, alkylpyrazolium, alkyloxazolium, alkylthiazolium, alkylpyridinium, alkylpyrimidinium, alkylpyridazinium, alkylpyra An organic cation selected from zinium, alkylpyrrolidinium, alkylphosphonium, alkylmorpholinium and alkylpiperidinium with fluorophosphate, fluoroalkyl-fluorophosphate, fluoroborate and fluoroalkyl-fluoro The fluorine-based anion selected from roborate may be an ionic liquid in an ion-bonded form.

Compared to hydrogen fluoride or ammonium fluoride, which are generally used as fluorine-containing compounds in the silicon substrate etching solution, fluorine-containing compounds provided in ionic liquid form have a higher boiling point and decomposition temperature, so they are decomposed during the etching process performed at high temperatures Accordingly, there is an advantage in that there is little possibility of changing the composition of the etching solution.

Hereinafter, specific embodiments of the present invention are presented. However, the examples described below are only for specifically illustrating or explaining the present invention, and the present invention is not limited thereto.

Experimental example One

An etching solution was prepared by mixing additives in the amounts shown in Table 1 below in 750 g of an 85 wt% aqueous solution of phosphoric acid.

division silane compound silicon oxide film
etch inhibitor Fluorine-containing compounds Kinds content
(ppm) Kinds content
(ppm) Kinds content
(ppm) Example 1 - - B-1 1000 - - Example 2 - - B-2 1000 - - Example 3 - - B-3 1000 - - Example 4 - - B-4 1000 - - Example 5 - - B-5 1000 C-1 1,000 Example 6 - - B-6 1000 - - Example 7 - - B-7 1000 - - Comparative Example 1 - - - - - - Comparative Example 2 A-1 1,000 - - - - Comparative Example 3 A-2 1,000 - - C-1 1,000

B-1:

B-2:

B-3:

B-4:

B-5:

B-6:

B-7:

In Examples 1 to 7 and Comparative Example 1, no silane compound was used, whereas Comparative Examples 2 and 3 were 3-aminopropylsilanetriol (A-1) and tetrahydroxysilane (A) as silane compounds. -2) was used. The fluorine-containing compound used in Example 5 and Comparative Example 3 is hydrofluoric acid (HF).

After heating the etching solution to 165° C., the silicon oxide layer and the silicon nitride layer were immersed for 3 minutes to etch. The thickness of the silicon oxide film and the silicon nitride film before and after the etching was measured using an ellipsometer (Nano-View, SE MG-1000; Ellipsometery), and the measurement result is an average value of five measurement results. The etch rate is a value calculated by dividing the thickness difference between the silicon oxide film and the silicon nitride film before and after the etching by the etching time (3 minutes). After completion of the etching, the etching solution was analyzed with a particle size analyzer to measure the average diameter of silicon-based particles present in the etching solution.

The measured etching rates and average diameters of silicon-based particles in the etching solution are shown in Table 2 below.

division Silicon-based particles
Average diameter (μm) silicon oxide film
Etch rate (Å/min) silicon nitride film
Etch rate (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 Example 6 <0.01 1.94 59.77 Example 7 <0.01 1.65 60.02 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 including other additives in the etching solution as in Comparative Example 1, silicon-based particles were hardly generated, but it can be seen that the selectivity for the silicon nitride film compared to the silicon oxide film was low.

On the other hand, when the silane compound was used as in Comparative Example 2, the etching rates for the silicon oxide film and the silicon nitride film were generally decreased compared to the Example, but silicon-based particles having a size of several tens of micrometers were generated.

According to Comparative Example 3, by using the fluorine-containing compound, compared to Comparative Example 2, the etching rate for the silicon oxide film and the silicon nitride film was overall increased, and it can be confirmed that the etching rate for the silicon oxide film was increased. In addition, in the case of Comparative Example 3, silicon-based particles having a larger size than Comparative Example 2 were generated.

On the other hand, according to Examples 1 to 4, it can be seen that silicon-based particles exist in a fairly fine size or are hardly generated, and the selectivity of the silicon nitride film to the silicon oxide film is also improved.

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

In the above, although an embodiment of the present invention has been described, those of ordinary skill in the art can add, change, delete or add components within the scope that does not depart from the spirit of the present invention described in the claims. It will be said that various modifications and changes of the present invention can be made by, and this is also included within the scope of the present invention.

Claims (11)

inorganic acid aqueous solution; and
a silicon oxide layer etch inhibitor represented by the following formula (1);
containing,
Silicon substrate etching solution:
[Formula 1]

here,
R ₁ and R ₂ are independently of each other 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 substituted 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 C ₇ -C ₃₀ aralkyl,
R ₃ and R ₄ are each independently hydrogen or methyl.
According to 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.
According to claim 1,
R ₁ and R ₂ are each independently a functional group selected from the group consisting of heteroalkyl, alkenyl, alkynyl, haloalkyl and aminoalkyl, and the functional group is branched with 3 or more carbon atoms,
Silicon substrate etching solution.
According to claim 1,
at least one of R ₃ and R _{4 is methyl;}
Silicon substrate etching solution.
According to claim 1,
The silicon oxide film etch inhibitor is a silicon-hydroxy group (-Si-OH) present on the surface of a silicon substrate or a silicon oxide film, a silicon-alkylcarboxyl group (-Si-CR ₃ R ₄ -CO ₂ H) or silicon-alkyl Substituted with an ester group (-Si-CR ₃ R ₄ -CO ₂ R ₁ or -SiCR ₃ R ₄ -CO ₂ R _{2 ),}
Silicon substrate etching solution.
According to claim 1,
In the silicon substrate etching solution, the silicon oxide film etch inhibitor is contained in an amount of 200 to 50,000 ppm,
Silicon substrate etching solution.
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 bifluoride and ammonium hydrogen fluoride,
Silicon substrate etching solution.
8. The method of claim 7,
The fluorine-containing compound is a compound having an ionic bond between an organic cation and a fluorine-based anion,
Silicon substrate etching solution.
10. The method of claim 9,
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.
10. The method of claim 9,
wherein the fluorine-based anion is selected from fluoride, fluorophosphate, fluoroalkyl-fluorophosphate, fluoroborate and fluoroalkyl-fluoroborate;
Silicon substrate etching solution.