KR102284211B1 - Method for preparing etching solution - Google Patents

Abstract

The present invention relates to a method for preparing an etching solution, and more particularly, to a method for preparing an etching solution capable of improving solubility and dispersibility of a silicon-based additive in an etching solution.

Description

Manufacturing method of etching solution {METHOD FOR PREPARING ETCHING SOLUTION}

The present invention relates to a method for preparing an etching solution, and more particularly, to a method for preparing an etching solution capable of improving solubility and dispersibility of a silicon-based additive in an etching solution.

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, an etching solution prepared by dispersing a silicon-based additive in phosphoric acid is used to increase the etching rate of the silicon nitride layer and decrease the etching rate of the silicon oxide layer.

In this case, the dispersibility of the silicon-based additive in phosphoric acid is related to the etching rate of the silicon oxide layer. That is, when the silicon-based additive in phosphoric acid is evenly dispersed, the variation in the etching rate for the silicon oxide film is small and constant. On the other hand, if the dispersibility of the silicon-based additive in phosphoric acid is poor, there is a problem in that the etching rate for the silicon oxide film is greatly varied.

An object of the present invention is to provide a method for preparing an etching solution capable of improving the solubility and dispersibility of a silicon-based additive in the etching solution.

In particular, the present invention is to improve the dispersibility of silica in a phosphoric acid-based etching solution using silica as a silicon-based additive to provide a method for preparing an etching solution capable of lowering the fluctuation of the etching rate for the silicon oxide film during etching of a silicon substrate. The purpose.

In order to solve the above technical problem, according to an aspect of the present invention, (a) preparing a mixed solution by mixing an aqueous inorganic acid solution and silica, and (b) an etching solution comprising the steps of applying electromagnetic waves to the mixed solution A method of manufacturing is provided.

Here, it is possible to prepare an etching solution having improved solubility and dispersibility of silica in the mixed solution by applying electromagnetic waves to a mixed solution in which an inorganic acid aqueous solution and silica are mixed.

In this case, electromagnetic waves applied to the mixed solution may be microwaves or ultraviolet rays.

According to the present invention, it is possible to improve the solubility and dispersibility of the silicon-based additive, particularly silica, in the etching solution, and through this, it is possible to lower the variation in the etching rate for the silicon oxide layer when the silicon substrate is etched.

In addition, there is an advantage in that it is possible to secure sufficient solubility and dispersibility of the silicon-based additive in the etching solution even when less energy and time are consumed compared to simple heating for dissolving and dispersing the silicon-based additive in the etching solution.

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.

Herein, the alkyl group R _a (a is an integer of 1 to 6) includes C ₁ -C ₁₀ alkyl, C ₆ -C _{12 cycloalkyl and C 2} -C ₁₀ heteroalkyl containing 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.

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.

As used herein, cycloalkyl or heterocycloalkyl containing a hetero atom will 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.

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 a form indirectly bonded by ^{sp 3 -hybrid carbon of alkyl.}

Hereinafter, a method for preparing an etching solution according to the present invention will be described in detail.

According to an aspect of the present invention, there is provided a method for preparing an etching solution comprising the steps of (a) preparing a mixed solution by mixing an aqueous inorganic acid solution and silica, and (b) applying an electromagnetic wave to the mixed solution.

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 prevents the various types of silicon-based additives present in the etching solution from changing into silicon-based particles.

Here, the inorganic acid constituting the inorganic acid aqueous solution is preferably a polar molecule. When electromagnetic waves, particularly microwaves, are applied to polar molecules, aligned rotation can be performed instead of random vibrations because the polar molecules rotate according to the wavelength of the electromagnetic wave.

At this time, the polar molecules that rotate aligned by microwaves may increase frictional heat with adjacent silica, thereby promoting dissolution and dispersion of silica in the inorganic acid aqueous solution.

The silica used in the present invention is preferably present in an amount of 100 to 5,000 ppm in the mixed solution, and more preferably, the silica is included in an amount of 100 to 2,500 ppm.

When the amount of silica in the mixed solution is less than 100 ppm, the effect of dissolving and dispersing silica obtained by applying electromagnetic waves to the mixed solution is inevitably insignificant. In addition, the protective effect of the silicon oxide layer by the silica in the etching solution, which is the final product, may be insufficient.

On the other hand, when the content of silica in the mixed solution exceeds 5,000 ppm, the possibility of polar interaction (eg, hydrogen bonding) between silica in the etching solution as the final product may increase.

In this case, there is a fear that the dispersibility of silica in the etching solution decreases due to aggregation between the silicas, thereby reducing the protective effect on the silicon oxide layer. In addition, there is a risk that the reversed-phase silica itself may grow into micrometer-sized silicon-based particles due to aggregation between silicas. The silica used in the present invention may be provided in the form of colloidal silica or fumed silica. In addition, the silica used in the present invention may be a reverse phase silica in which (A) a hydroxyl group (-OH) bonded to a silicon atom at the surface and a terminal is substituted with (B) a saturated or unsaturated hydrocarbon group.

Here, the reverse phase silica is generally a silica in which (A) a hydroxyl group (-OH) bonded to a silicon atom on the surface and a terminal of the hydrophilic silica is substituted with (B) a saturated or unsaturated hydrocarbon group or (C) a siloxane group. it means.

Reversed silica has a form in which a hydroxyl group (-OH) is bonded to some of the silicon atoms present at arbitrary positions on the surface and at the ends, so it is attached to the surface of the silicon oxide film through a polar interaction with the silicon oxide film to form silica. It is possible to form a passivation layer.

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

In addition, the reverse phase silica is capable of forming a hydrophobic surface as hydrocarbon groups are bonded to silicon atoms present on the surface and at the ends. Accordingly, since it is possible to impart a certain level of steric hindrance between adjacent reversed silicas, it is possible to prevent the inversed silicas from being aggregated to form silicon-based particles.

According to an embodiment of the present invention, the reverse phase silica in which (A) a hydroxyl group (-OH) bonded to a silicon atom at the surface and a terminal of the silica is substituted with a saturated or unsaturated hydrocarbon group is represented by the following formula (1) contains 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 containing at least one hetero atom, C ₂ -C ₁₀ alkenyl and A hydrocarbon group or a hydroxy group selected from C ₂ -C _{10 alkynyl, and at least one of R 3} to R ₆ is a hydrocarbon group.

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

In this case, the dispersibility of the reverse phase silica in the etching solution is deteriorated due to aggregation between the reverse phase silicas, and there is a fear that the protective effect on the silicon oxide layer may be reduced. In addition, there is a risk that the reversed-phase silica itself may grow into micrometer-sized silicon-based particles due to aggregation between the reversed-phase silicas.

On the other hand, when the ratio of (A) hydroxyl groups (-OH) bonded to the silicon atoms 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, so that the protective effect of the reverse phase silica is reduced. may be difficult to implement. In addition, when electromagnetic waves are applied to dissolve and disperse the reverse phase silica in the aqueous inorganic acid solution, when the ratio of (A) hydroxyl groups (-OH) bonded to the silicon atoms at the surface and the terminal of the reverse phase silica is extremely small, the wavelength of the electromagnetic wave There is a fear that the aligned rotation of the reverse phase silica is insufficient.

Herein, the reverse phase silica may include only the repeating unit represented by Formula 1, but a hydroxyl group is bonded to any silicon atom positioned between the repeating units represented by Formula 1 before or after the repeating unit represented by Formula 1 may have a given form.

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

[Formula 1-1]

Here, m and m' mean the number of repeating units represented by the formula (1), and m and m' may be appropriately selected so that the average diameter of the reversed-phase silica exists in the range of 1 nm to 10 μm.

The average diameter of the reverse phase silica used in the etching solution according to the present invention is preferably 5 nm to 10 μm.

When the average diameter of the reversed silica is less than 5 nm, the tendency to participate in the reaction is reduced, so that there may be little protective effect on the silicon oxide layer during etching.

In addition, when the reverse phase silica is etched by the fluorine-containing compound as the fluorine-containing compound and the reverse phase silica are used together to increase the etching rate for a silicon substrate (eg, a silicon nitride film), the size of the reverse phase silica is There is a risk of losing the protective ability to the silicon oxide film because it is inevitably finer.

In addition, when reverse-phase silica having an average diameter of less than 1 nm is used together with a fluorine-containing compound, silicon atoms constituting the reverse-phase silica _{are etched in the form of SiF 4} , and there is a fear that the concentration of reverse-phase silica in the etching solution is changed.

On the other hand, when the average diameter of the reversed silica exceeds 10 μm, there is a risk of growth into silicon-based particles of several to tens of micrometers due to the interaction between the reversed silica.

According to the present invention, it is possible to prepare an etching solution with improved solubility and dispersibility of silica in the mixed solution by applying electromagnetic waves to a mixed solution in which an inorganic acid aqueous solution and silica are mixed (step (b)).

In this case, the electromagnetic wave applied to the mixed solution may be at least one selected from microwaves and ultraviolet rays.

For example, microwaves or ultraviolet rays may be applied to the mixed solution, microwaves and ultraviolet rays may be simultaneously applied to the mixed solution, or microwaves and ultraviolet rays may be sequentially applied to the mixed solution.

In the prior art, silica was dispersed or dissolved by applying heat to the mixed solution, but the present invention is characterized in that silica is dispersed or dissolved only by electromagnetic waves without a process or means for applying heat.

However, after the process of applying electromagnetic waves, a heating process for maintaining the dispersed or dissolved state may be accompanied, and this may be done in a space without microwaves or ultraviolet rays, which are means for applying electromagnetic waves.

In particular, in the case of microwaves, the mixed solution may be placed in a transparent or translucent container such as quartz or a container through which electromagnetic waves can pass, and the mixture may be introduced into a process equipped with a microwave providing means. Considering the acidic condition of the solution, it is also possible to protect the solution with an acid-resistant material (such as quartz), and then add a microwave providing means to the mixed solution.

In one embodiment, when the electromagnetic wave applied to the mixed solution is a microwave, silica having a predetermined diameter performs aligned rotation by the microwave.

The preferred wavelength of the microwave for the ordered rotation of silica is 200 MHz to 20 GHz, and the rating power is 0.5 KW to 10 KW. The rotation or vibration of silica may be implemented within the above conditions, and if the wavelength of the microwave is too short, it may affect the silica molecular structure, whereas if the wavelength of the microwave is too long, it may not be able to deliver sufficient energy to the silica. there is.

The silica in the aligned rotation has a greater frictional force with the adjacent silica than the silica that does not rotate or randomly vibrates, so it is possible to dissolve and disperse into a mixed solution within a relatively short time.

In another embodiment, when the electromagnetic wave applied to the mixed solution is ultraviolet, decomposition of silica by radicals generated by the ultraviolet is accelerated, so that it is possible to improve the solubility and dispersibility of silica in the mixed solution.

As a method of irradiating ultraviolet rays, similar to the method of irradiating microwaves, a method of putting the mixed solution in a container and putting the ultraviolet light providing means, or putting the ultraviolet light providing means surrounded by an acid-resistant material into the mixed solution may be used.

In particular, when a fluorine-containing compound is further added to the mixed solution before applying ultraviolet rays, fluorine radicals may be generated by ultraviolet rays, and the fluorine radicals may further accelerate the decomposition of silica.

A preferred wavelength of ultraviolet light for radical generation in the mixed solution is 175 nm to 300 nm.

The fluorine-containing compound can serve as a source of fluorine radicals when irradiated with ultraviolet rays and further improve the etching rate of a silicon substrate (particularly, a silicon nitride layer) in an etching solution, which is a final product.

When the etching solution prepared according to the present invention is used, since the silicon oxide layer may be protected by the reverse phase silica, etching of the silicon oxide layer by the fluorine-containing compound may be reduced.

The fluorine-containing compound used in the present invention is preferably present in an amount of 10 to 2,500 ppm in the mixed solution.

When the amount of the fluorine-containing compound in the mixed solution is less than 10 ppm, the amount of fluorine radicals generated by UV irradiation is small, so that the effect of dissolving and dispersing silica by the fluorine radicals is insignificant.

On the other hand, when the content of silica in the mixed solution exceeds 2,500 ppm, the content of the fluorine-containing compound in the etching solution, which is the final product, is excessively high, so that the etching rate for the silicon oxide layer may increase.

According to another embodiment of the present invention, an electromagnetic wave may be applied at the same time as silica is mixed with the inorganic acid aqueous solution.

Accordingly, it is possible to further improve the solubility of silica in the inorganic acid aqueous solution by applying electromagnetic waves from the initial stage in which the inorganic acid aqueous solution and silica are mixed. In addition, there is an advantage that a solution in which silica is effectively dispersed in the inorganic acid aqueous solution can be obtained immediately after the mixing of the inorganic acid aqueous solution and the silica is completed.

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 etching solution, the fluorine-containing compound provided in the form of an ionic liquid has a high boiling point and decomposition temperature. As it is decomposed during the etching process performed at high temperature There is an advantage in that there is little possibility of changing the composition of the etching solution.

According to another embodiment of the present invention, the step of heat treatment after applying electromagnetic waves to the mixed solution may be additionally performed.

In particular, when the electromagnetic wave applied to the mixed solution is ultraviolet light, energy required for the fluorine radicals generated by ultraviolet irradiation to react with silica may be supplied through additional heat treatment.

In this case, a direct heating method may be used for the heat treatment or a method of irradiating microwaves, which is a type of electromagnetic wave, may be used.

That is, when ultraviolet rays are applied to the mixed solution to generate fluorine radicals and then microwaves are applied, the energy required for the reaction between the fluorine radicals and silica is supplied as well as inducing ordered rotation of polar molecules in the mixed solution, resulting in friction It can further promote dissolution and dispersion of silica.

The silicon substrate to be etched by the etching solution according to the present invention _{preferably includes at least a silicon oxide layer (SiO x} ), and may include a silicon oxide layer and a silicon nitride layer (Si _x N _y , SI _x O _y N _z ) at the same time. . 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.

When the etching solution prepared according to the present invention is used, it is possible to form a protective film on the surface of the silicon substrate, in particular, the silicon oxide film by the silica evenly dissolved and dispersed in the etching solution.

Accordingly, it is possible to reduce the rate at which the silicon oxide layer 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.

In addition, as silica is uniformly dissolved and dispersed in the etching solution, it is possible to further improve the etching quality by reducing the deviation of the etching rate for the silicon oxide layer.

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

Preparation of etching solution

A mixed solution was prepared by mixing 200 ppm of fumed silica (average diameter of 100 nm) with 750 g of an 85% aqueous phosphoric acid solution. Then, an etching solution was prepared by dividing it into a heating method in which heat was directly applied to the mixed solution to dissolve and disperse the fumed silica in the aqueous phosphoric acid solution and a heating method in which electromagnetic waves were applied to dissolve and disperse the fumed silica in the aqueous phosphoric acid solution.

Example 1

A microwave of 400 MHz wavelength was applied for 1 hour so that the mixed solution was maintained at 165° C. to dissolve and disperse the fumed silica in the mixed solution.

Example 2

To the mixed solution to which 50 ppm of ammonium fluoride was additionally added, ultraviolet light of 220 nm wavelength was applied for 1 hour, and then the mixed solution was heated for 30 minutes to maintain 165° C. to dissolve and disperse the fumed silica in the mixed solution.

Example 3

To the mixed solution to which 50 ppm of ammonium fluoride was additionally added, a 220 nm wavelength ultraviolet light was applied for 1 hour, and then a microwave of 400 MHz wavelength was applied for 30 minutes so that the mixed solution was maintained at 165° C. to dissolve and disperse the fumed silica in the mixed solution. did it

Comparative Examples 1 to 3

Heat was applied directly for 1 hour (Comparative Example 1), 2 hours (Comparative Example 2), and 3 hours (Comparative Example 3) so that the mixed solution was maintained at 165° C. to dissolve and disperse the fumed silica in the mixed solution.

Evaluation of the etching solution

When etching a silicon substrate (for example, a silicon substrate in which a silicon oxide film and a silicon nitride film exist simultaneously) using etching solutions prepared by different heating methods, the following is to examine the effect of the etching solution on the silicon oxide film The effect of the etching solution on the silicon oxide film was evaluated as shown.

First, a silicon substrate including a thermal oxide layer was immersed in an etching solution heated to 165° C. for 3 minutes to etch. The thickness of the silicon oxide film before and after etching was measured five times using an ellipsometer (Nano-View, SE MG-1000; Ellipsometery). The etching rate was calculated by dividing the difference in the thickness of the silicon oxide film and the silicon nitride film before and after the etching by the etching time (3 minutes).

division round thickness before etching
(nm) thickness after etching
(nm) etch rate etch rate
Standard Deviation Comparative Example 1 One 1037.52 1036.42 1.30 0.6128
2 1036.87 1036.79 0.08 3 1037.44 1036.07 1.57 4 1038.03 1037.46 0.47 5 1037.61 1037.29 0.62 Comparative Example 2 One 1035.52 1034.50 1.02 0.4354
2 1034.57 1034.34 0.23 3 1033.96 1032.73 1.23 4 1034.53 1034.19 0.34 5 1033.81 1032.93 0.88 Comparative Example 3 One 1032.12 1031.14 0.98 0.2951
2 1032.444 1032.01 0.43 3 1033.11 1032.33 0.78 4 1032.85 1032.60 0.25 5 1033.05 1032.60 0.45 Example 1 One 1036.15 1035.30 0.86 0.0819 2 1036.85 1036.07 0.78 3 1035.42 1034.51 0.91 4 1035.91 1035.22 0.69 5 1036.21 1035.40 0.81 Example 2 One 1035.09 1034.30 0.79 0.0521 2 1033.91 1033.10 0.81 3 1034.87 1033.98 0.89 4 1035.96 1035.05 0.91 5 1036.47 1035.63 0.84 Example 3 One 1034.51 1034.36 0.15 0.184 2 1032.94 1032.76 0.18 3 1036.19 1035.96 0.23 4 1035.61 1035.44 0.17 5 1035.78 1035.59 0.19

Looking at the results of Comparative Example 1, it can be seen that the deviation of the etching results (etch thickness and etching rate) for the silicon oxide film for each etching cycle is severe. Looking at the results of Comparative Examples 2 and 3, it is directly compared to Comparative Example 1 As the heating time increases, it can be seen that the deviation of the etching result (etch thickness and etching rate) for the silicon oxide film for each etching cycle decreases.

That is, when the direct heating time is only 1 hour as in Comparative Example 1, the dissolution and dispersion of silica in the etching solution is not sufficiently performed, so the etching result is greatly varied. However, as the direct heating time increases, the silica in the etching solution is gradually dissolved. and dispersion, indicating that the deviation of the etching results in Comparative Examples 2 and 3 compared to Comparative Example 1 is somewhat reduced.

On the other hand, in the case of indirect heating using microwaves (Example 1), as in Comparative Example 1, the heating time was only 1 hour, but the standard deviation of the etching rate was only 0.0519, so the deviation of the etching result compared to Comparative Examples 1 to 3 It can be seen that there is a significant decrease in

Unlike direct heating, silica in the etching solution undergoes aligned rotation by microwaves, and silica with aligned rotation does not rotate or has a larger size with adjacent silica than silica with random vibration. This is because it is possible to dissolve and disperse into a mixed solution within a relatively short time by having frictional force.

On the other hand, in the case of Example 2, which was directly heated after UV irradiation, the heating time was only 30 minutes, but the standard deviation of the etching rate was only 0.0521, so it was confirmed that the deviation of the etching results compared to Comparative Examples 1 to 3 was significantly reduced. can

The fluorine-containing compound present in the mixed solution generates fluorine radicals by UV irradiation, and these fluorine radicals promote dissolution and dispersion of silica to sufficiently dissolve and disperse silica in the mixed solution even when heated for a shorter time than in Comparative Examples. it is possible to do

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 (9)

(a) preparing a mixed solution by mixing an aqueous inorganic acid solution and silica; and
(b) applying electromagnetic waves to the mixed solution;
including,
(A) hydroxyl group (-OH) bonded to the silicon atom on the surface and terminal of the silica is (B) reversed-phase silica substituted with a saturated or unsaturated hydrocarbon group,
A method for preparing an etching solution.
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,
A method for preparing an etching solution.
delete According to claim 1,
The average diameter of the silica is 1 nm to 10 μm,
A method for preparing an etching solution.
5. The method of claim 4,
The electromagnetic wave is at least one selected from microwaves and ultraviolet rays,
A method for preparing an etching solution.
6. The method of claim 5,
The wavelength of the microwave is 200 MHz to 20 GHz,
A method for preparing an etching solution.
6. The method of claim 5,
The wavelength of the ultraviolet is 175 nm to 300 nm,
A method for preparing an etching solution.
According to claim 1,
Further comprising the step of mixing the fluorine-containing compound before applying electromagnetic waves to the mixed solution,
A method for preparing an etching solution.
According to claim 1,
Steps (a) and (b) are performed simultaneously,
A method for preparing an etching solution.