KR19990075903A - Electronic display device and cleaning and etching composition for substrate - Google Patents

Abstract

The present invention provides a cleaning and etching composition that effectively removes contaminants generated during the manufacture and processing of various electronic display devices and substrates while protecting the substrate.

In the case of using the composition of the present invention using fluoride salts and persulfates as essential components, not only a uniform reproducibility can be obtained for cleaning the substrate, but also only a portion to be etched can be selectively removed, thereby improving surface roughness.

Description

Cleaning and Etching Compositions for Electronic Displays and Substrates

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to cleaning and etching compositions for electronic display devices and substrates, and more particularly to contaminants on SiO ₂ during the manufacture and processing of electronic display devices, quartz equipment and semiconductor substrates using fluoride salts and persulfates. The present invention relates to a composition that effectively removes only contaminants by cleaning or etching.

In the manufacture and processing of various electronic display devices and substrates, cleaning and etching processes are required. For example, the manufacturing process of a cathode ray tube (CRT) in an electronic display device is a 10-18% hydrofluoric acid cleaning, followed by graphite coating, phosphor coating, racker coating, aluminum deposition, funnel embedded graphite coating, The panel is then bonded to the funnel, the outer graphite is applied to the funnel, the neck washed, enclosed and evacuated, followed by the outer coating of the panel. The outer coating material is composed of In ₂ O ₃ , Sb ₂ O ₃ , SnO ₂ , SiO ₂ , and removes contaminants with 1-2% hydrofluoric acid or ammonium hydrogen fluoride before forming the coating layer. The defective coating film is a 10-30% ammonium bifluoride solution before firing, and after firing, a step of polishing with CeO ₂ is required.

In addition, the LCD process, which is one of the electronic display devices, also includes an etching process in a cleaning process and a lithography process. It is very important to secure the uniformity of etching over the entire surface of a large substrate, which is a process requiring high precision.

If you list the example of the etching solution according to the type of thin film to be cleaned and etched in the LCD,

Cleaning formula (SiO ₂ ) 1.H ₂ SO ₄ : H ₂ O ₂ (6: 1), 120 ° C.2.50% HF: H ₂ O (1: 100 to 1000) 3.NH ₄ OH: H ₂ O ₂ : H ₂ O (1: 1: 7) SC-14.HCl: H ₂ O ₂ : H ₂ O (1: 1: 6) SC-25.Pure wash Etch Prescription (SiO ₂ ) 1.40% NH ₄ F: 50% HF (7: 1) BOE2. 40% NH ₄ F: 50% HF (7: 1) + H ₂ O ₂ Etch Prescription (SiNx) H ₃ PO ₄ : H ₂ O (85: 1) or 40% NH ₄ F: 50% HF (20: 1)

The conditions required for the composition of the cleaning and etching include cleaning and etching rate control, selectivity control between the upper and lower layers, etching shape control, etching control in a multilayer film, stability and uniformity and reproducibility of the composition solution.

In wafer fabrication, quartz equipment is required as a peripheral device for processing wafers, and the manufacturing process is as follows: raw material-cleaning (11-16.5% hydrofluoric acid solution, 2-3 minutes) -waxing-cutting and machining -Dewaxing-Ultrasonic cleaning-Cleaning (15% hydrofluoric acid solution, 5 minutes) -Bench Assembly-Cleaning (11-16.5% hydrofluoric acid solution, 5 minutes)-Drying-Heat treatment (1200 ° C)-Cleaning (11-16.5% hydrofluoric acid solution) , 5 minutes)-dry.

Through the above process, the oxide film generated in various contaminants and heat treatment processes is removed. In this case, a high concentration of hydrofluoric acid is used. At this time, problems of flatness, damage and cracking of the material occur. Furthermore, the quartz apparatus thus manufactured is used in the heat treatment process and the various deposition film processes in the wafer manufacturing process, and a hydrofluoric acid solution (2 to 25%) is used to remove contaminants attached thereto.

The manufacturing and assembly process of the semiconductor wafer is shown below.

I. Semiconductor Substrate Manufacturing Process

1. Monocrystalline Silicon

2.silicone cutting

3. Surface lapping (approx. 60㎛ mechanical polishing)

4. Chemical etching (about 30㎛ etching)

5. Surface polishing (etched about 10㎛ over 3 times to get the desired surface roughness)

6. Cleaning

II. Semiconductor Board Assembly Process

7. Initial cleaning

8. Oxidation process: Si on substrate surface

9. Diffusion: Si / SiO ₂ / Si ₃ N ₄ coexists on the surface of the substrate before diffusion

10. Ion implantation: Before the ion implantation, the substrate surface coexists with SiO ₂ / Si ₃ N ₄

11. Epitaxy Growth: The substrate surface before epitaxial growth is Si

12. Insulating film, conductive film formation (CVD; chemical vapor deposition): polySi / SiO ₂ coexistence

13. Electrode Formation (PVD): Si / SiO ₂ coexists on the substrate surface before electrode formation

* Paragraphs 8 to 13 involve a photolithography process.

As such, the silicon substrate undergoes chemical etching of silicon and silicon oxide depending on the process, and also removes ionic contamination, nonionic contamination, and other particulate contamination formed on SiO ₂ depending on the surface of the substrate. There is a need.

Looking at the process that requires cleaning and etching in the semiconductor manufacturing and assembly process in more detail, in the oxidation process (8) is a process of pre-washing with a solvent, sulfuric acid, hydrogen peroxide, etc. before the oxide film is grown in the oxide film production process 100-200 얇은 thin oxide film formed during the removal process with hydrofluoric acid (HF: H ₂ O = 10: 1), and in the diffusion process, a mixture of sulfuric acid and hydrogen peroxide is used to remove impurities from the wafer surface before diffusion. After heating the mixture of ammonium hydroxide and hydrogen peroxide and immersing for 10-20 minutes to remove organic contaminants and ionic contaminants, in this case, an unnecessary oxide film is formed on the exposed silicon surface. The process of immersing and washing the wafer in the solution,

In the photolithography process, an etching solution is used to define a portion to be diffused or ion implanted by an etching and a portion to be protected.In this case, the etching is a process in which thin films grown or deposited under the photoresist film after the photoresist development process are used for the purpose of the process. As a selective removal process, the portion covered by the photoresist film is protected and remains during the etching operation, and the exposed thin film is etched away.

Etching can also be divided into wet etch (wet etch or chemical etch) and dry etch (dry etch or plasma etch) and includes a photoresist removal process.

The double wet etching refers to a method of etching using a chemical solution that can chemically react with and dissolve the thin film to be etched, and the chemical solution or composition ratio to be used varies depending on the characteristics of the thin film.

The general wet etching principle of the oxide film is as follows.

The oxide film can be roughly divided into a growth oxide film and a deposition oxide film, and any type of oxide film utilizes the property of dissolving the oxide film in hydrofluoric acid.

HF → H ^{+ +} F ^-

The dissociated fluorine ions react with the oxide film to etch, which is represented by the following equation:

SiO ₂ + ₄ HF → SiF ₄ + 2H ₂ O

2HF + SiF ₄ = H ₂ SiF ₆

As can be seen in the above two equations, the fluorine ions are consumed as the etching continues, and the concentration of hydrogen ions in the solution decreases as the solution itself is diluted with water. As a result, the etching rate of the oxide film changes each time the process is repeated. This deviates from the process objective of obtaining a uniform and reproducible result in a very unstable state of the process.

A new solution is added to remove the change in the hydrogen ion concentration or the etching rate to obtain a uniform result, which can be stabilized by adding ammonium fluoride (NH ₄ F).

The ammonium fluoride is dissociated into ammonium ions and fluorine ions as shown in the following formula, in which fluorine ions participate in an etching reaction.

NH ₄ → NH ₄ + F ^-

In other words, it serves to cover the fluorine ions consumed in the etching reaction, thereby maintaining the etching rate uniformly by making the hydrogen ion concentration in the solution constant. Ammonium ions, on the other hand, have no effect on the etching reaction and thus satisfy the process purpose.

In wet etching, however, isotropic etching occurs because chemical reactions occur not only vertically but also horizontally. As a result, an undercut phenomenon always occurs in which the end portion of the thin film to be protected by the photoresist is etched in a circle. This is the biggest drawback of wet etching, which is limited to integrated circuits with narrow line widths, making them difficult to use in device manufacturing processes.

In addition, in the case of single crystal silicon or a metal layer, after oxidizing these thin films using an oxidant, the oxidized thin films are etched. Both thin films use nitric acid as an oxidizing agent. When single crystal silicon is oxidized, it is converted into an oxide film, which is etched with hydrofluoric acid.

In treating silicon oxide, an aqueous solution based on hydrofluoric acid, that is, hydrofluoric acid buffered solution (BHF), is used. The reaction formula is as follows.

_{4nHF + SiO 2 = SiF 4 ↑} + 2H 2 O + nH - ↑ + nF - ↑ 1)

2HF + SiF ₄ = H ₂ SiF ₆ 2)

In addition, for example, heavy metals such as Fe, Cu, Au, and metals which are difficult to ionize, such as Al, may be HPM (HCl / H ₂ O ₂ ), SPM (H ₂ SO ₄ + H ₂ O ₂ ), aqua regia (HCl + HNO). ₃ ) As the acidic oxidant of ₃ ) is removed by heating, a natural oxide film is formed on the wafer, and to solve this problem, DHF (HF / H ₂ O) is used to clean it. Furthermore, metals such as Cu, which have less ionization tendency, are removed from the wafer surface. In order to solve the problem of precipitation, a cleaning solution having H ₂ O ₂ added to DHF has been developed.

However, as time passes, hydrogen peroxide water is rapidly decomposed into water and generator oxygen, and hydrogen peroxide is depleted, and hydrofluoric acid in the composition is easily scattered, and chemical composition of the composition is changed, which makes it difficult to maintain uniformity of cleaning and etching solutions.

In addition, the silicon fluoride (SiF ₄ ) generated in the reaction formula (1) reacts with water to generate colloidal silicon oxide (SiO ₂ ) and is easily attached to the activated wafer. If fine particles of silicon oxide remain on the surface of the wafer, they may form stains or stains due to staining.

Further, although the etching rate is an important operation variable due to the characteristics required for the wafer, planarization is required as uniform fine irregularities in surface irregularities after cleaning and etching for high integration.

In addition, if a large amount of colloidal silicon oxide and hydrofluoric acid accumulate in the treatment liquid over time, a large amount of wastewater is generated. Therefore, the problem of extending the life of the liquid and treating the wastewater is also one of the challenges to be solved.

Accordingly, the present invention is to provide a cleaning and etching composition having high flatness and gloss while minimizing damage on the substrate when cleaning and etching the SiO ₂ surface during the manufacture and assembly of electronic display devices, quartz equipment and semiconductor substrates. It is.

According to the present invention, in cleaning and etching the SiO ₂ surface on the substrate,

a) 0.1-50% by weight, based on the total amount of the total composition,

b) 0.1-50% by weight persulfate, based on the total amount of the total composition and

As an optional component, one or more kinds can be added from the group consisting of surfactants, accelerators and inhibitors,

Provided are cleaning and etching compositions for electronic display devices, quartz equipment, and semiconductor substrates.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

In the present invention, the fluoride salt serves to etch SiO _{2. In} the assembling process of single crystal silicon and a semiconductor wafer, a fluoride salt is used to etch the surface of the SiO ₂ phase. In the manufacturing and processing process, the surface of SiO ₂ is etched using fluoride salt.

The scheme is as follows.

6XF + SiO ₂ = X ₂ SiF ₆ + 2X ₂ O (3)

The fluoride salt dissolves the silicon oxide to generate a silicide to proceed with the etching reaction. The fluoride salt alone has a lower etch rate than that of hydrofluoric acid, but the cleaning and etching of the present invention is not a major problem because the fluoride salt is not focused on the etch rate but is intended to obtain flatness after treatment of the thin film to be removed.

In addition, in the waste water treatment, additives form F of (for example, HF ^HF) fluoride salts than the ionic form (e.g., NH ₄ HF ₂₎ F of ^- and ions are in fact removed coagulation is easy is known, the present invention The F ^- content of the composition of F is generally less F ^- ion than the concentration of HF used in the natural wild, thus reducing the cost of F ^- ion wastewater treatment.

Specifically usable fluoride salts are acidic ammonium fluoride (NH ₄ HF ₂ ), ammonium fluoride (NH ₄ F), sodium fluoride (NaF), acidic potassium fluoride (KHF ₂ ), acidic sodium fluoride (NaHF ₂ ), barium fluoride (BaF ₂ ), potassium fluoride (KF) and ammonium borohydride (NH ₄ BF ₄ ) can be selected from one or more kinds.

In addition, a persulfate are gradually decomposed in an aqueous solution, and so the higher the temperature quickly decomposing and substantially constant release of hydrogen peroxide by a very small amount, and serves to improve the oxidizing power, the SiO ₂ on the silicon hydrofluoric acid and colloid to be treated when generated by a predetermined amount It can be excluded that it is continuously attached to the workpiece.

The persulfate is selected from the group consisting of sodium persulfate (Na ₂ S ₂ O ₈ ), ammonium persulfate ((NH ₄ ) ₂ S ₂ O ₈ ) and potassium persulfate (k ₂ S ₂ O ₈ ) do.

Surfactants and inhibitors are optionally added to the composition consisting of the fluoride salts and persulfates according to the first aspect of the present invention to clean and finely etch SiO ₂ surfaces during the manufacture and assembly of electronic displays, quartz equipment and semiconductor substrates. do.

In this case, the inhibitor is used to remove the thin film on the metal depending on the type of the film to be removed. Such inhibitors include amines and amides. As accelerators for promoting the reaction, sulfuric acid, phosphoric acid and acetic acid are selected.

Where the amount available for each component is based on the weight of the total composition of the fluoride salt contains 0.1-50% by weight, preferably 0.4-12% by weight, persulfate 0.1-50% by weight, preferably 2-15 Wt%, the surfactant contains 0.01-5 wt%, preferably 0.02-3 wt%, the inhibitor component contains 0.01-10 wt%, preferably 0.1-3 wt%, the accelerator component Contains 0.05-20% by weight, preferably 1-10% by weight, the remainder being filled with purified water.

The amount of the fluoride salt is closely related to the etching rate of SiO ₂ , and the etching rate is proportional to the amount of F ⁻ ions in the fluoride salt. That is, the content of the fluoride salt is used at a low concentration when used as a composition as a cleaning liquid, and a high concentration when used as an etching liquid.

Persulfate is to help to increase the oxidizing power, and to increase and decrease the composition depending on the object to be removed, the amount is 0.2-40% by weight of the typical range. Hydrogen peroxide is also an effective substitute for persulfate, although it is difficult to maintain liquid uniformity.

Inhibitors and accelerators adjust the amount of addition according to each process, and the amount of each composition is adjusted according to the characteristics, requirements, economics, cleaning power, and etching rate of each process. It is also desirable to add an appropriate amount of surfactant to enhance the surface tension of the composition.

The surfactant may be selected from the group containing Na ions and / or SO ₃ ions and the fluorine-based surfactant group to play a wet role.

In addition, the composition according to the present invention may be diluted with purified water as necessary.

Furthermore, the fluoride salt and persulfate may be mixed and then transported and stored as a solid, and when used, may be dissolved in purified water and additionally added an additive such as a surfactant or an accelerator / inhibitor.

Furthermore, the composition according to the present invention can shorten the processes such as air or mechanical fluctuations, agitation, ultrasonic means, rotation of the object to be processed when used in the conventional immersion operation. That is, the treatment method can be shortened by selectively using appropriate conditions such as the type of device used, temperature, pressure, composition ratio, composition concentration, flow rate, fluctuation, ultrasonic use, mechanical stirring, dipping or spraying, and bubbling. Change is also possible.

Modification of the processing method is also within the scope of the technical idea of the present invention.

In addition, according to the present invention, by using a salt without the use of hydrofluoric acid and nitric acid, it is possible to extend the life of the composition and to easily treat wastewater, and to obtain uniform reproducibility even when repeated.

<Example>

The following examples are provided to illustrate the invention in detail.

Example 1 Preparation of Cleaning and Etching Compositions

A cleaning and etching composition for treating SiO ₂ was prepared using the composition described in the following table.

Ingredient Acid Ammonium Fluoride (g / l) Persulfate (g / l) Surfactant (g / l) A 40 120 - B 40 120 5

* The remainder of the composition is filled with purified water.

Example 2: Comparison of Detergency Between Compositions

In order to compare the cleaning power, each step panel of the CRT was prepared as follows. All panels were 14 "in size.

a. Specimen (Panel) Before Inner Graphite Coating

b. Panel for regeneration due to poor internal graphite coating

c. Panel requiring regeneration due to poor fluorescent film

d. Panel after exterior coating

The composition of Example 1 had a head pressure of 5 m and a nozzle diameter of 20 mm, and the cleaning surface and the nozzle tip were washed at a distance of 20 cm. Determination of the cleaning power according to the specimen and the composition was tested for the time it takes for the water to evenly adhere to the front surface of the specimen and the results are shown below.

Psalter Composition Processing time (seconds) Treatment temperature (℃) Processing result a A 8 25 Hydrophilic a B 6 25 Hydrophilic a 10% HF 10 25 Hydrophilic b A 10 25 Hydrophilic b B 8 25 Hydrophilic b 10% HF 12 25 Hydrophilic c A 25 25 Hydrophilic c B 20 25 Hydrophilic d 20% HF 30 25 Hydrophilic d B 10 25 Hydrophilic e 15% NH ₄ HF ₂ 15 25 Hydrophilic

As can be seen from the results, it can be seen that the cleaning rate of the composition of the present invention is faster than that of the conventional cleaning composition. Furthermore, it can be seen that the B composition containing the surfactant is treated with the composition to which the surfactant is added because the wetting and penetrating action to the object to be treated is enhanced and processed faster.

Example 3: Glossiness and Hydrophilicity Comparison

Specimen of Example 2 d. Panels (Size 15 inches, industrial) for recycling to poor coating after exterior coating were polished with conventional cerium oxide and washed with Composition B on the other hand. Polishing with CeO ₂ was carried out at a polishing pressure of 4 kg / cm ² .

The washing process of the composition B of the present invention was rubbed by hand with a cloth (pressure: 0.5 kg / cm ² or less). The glossiness and hydrophilicity comparison result with a regular product are shown in the following table.

division Glossiness Hydrophilic / hydrophobic confirmation Regular article 97.25% Over hydrophobic CeO ₂ Polishing 96.4% Over hydrophobic Composition B 97.25% Over hydrophilic

As shown in the above table, the glossiness was the same as that of the regular product, while foreign matter such as particles or organic substances remained on the treated surface of the regular product and appeared hydrophobic, while the cleaning treatment with the composition of the present invention was perfect. By forming the water film, the peeling phenomenon due to the oil film may be excluded.

In addition, although the surface polished with CeO ₂ is a cause of sparking defects due to the scratch phenomenon, the present invention can eliminate the scratch phenomenon.

Example 4 Weight Loss Comparison

200 ml of the 12% hydrofluoric acid solution and the composition according to the present invention were used in a beaker, followed by bubbling, and a specimen having a CRT size of 50 mm × 50 mm × 10 mm was deposited for 10 minutes. Treatment temperature at this time was 25 degreeC. The weight loss by etching of each composition was measured and listed in the table below.

division 12% HF Composition A Weight (g) Before treatment 36.78 35.78 After treatment 35.78 35.64 Weight loss (%) 2.72 0.39 F ^- amount of ions (ppm) 55,000 26,000

As can be seen from the above table, the etching rate of SiO ₂ is almost proportional to the fluorine ion content. However, in the case of hydrofluoric acid solution in which fluorine ions exist in a natural form, excessive etching occurs, and the weight loss amount of SiO ₂ is converted into a fluoride containing fluorine ions, so that the uniformity of the cleaning solution is faster than that of the cleaning solution according to the present invention. It is lost.

Example 5-1 (Comparative Example)

<Checking hydrophilicity of LCD and its processing time>

An untreated glass specimen of LCD having a size of 50 mm x 50 mm x 0.7 mm was prepared. This specimen was prepared by diluting the DNF (HF: H ₂ O = 1: 100) composition solution, which is one of the SiO ₂ cleaning prescription solutions in the prior art, and the composition B of Example 1 in a ratio of 1:50 with water. The composition of the present invention was immersed at 25 ° C. and then taken out to check the hydrophilicity and the treatment time thereof.

Composition DHF DHF Composition B: Water (1:50) Fluorine Ion Concentration in Composition (ppm) 475 475 532 Deposition time (sec) 30 40 20 Hydrophilicity Check Hydrophobic Hydrophilic Hydrophilic

As can be seen from the table, it can be seen that the cleaning composition according to the present invention is superior to DHF which is a conventional prescription liquid.

Example 5-2

<Processing test of SiNx and Al-Nb thin film on LCD substrate>

50 mm x 50 mm x 0.7 mm specimens were prepared in which thin films of SiNx and Al-Nb were laminated on the LCD substrate at a thickness of 3000 mm and 2500 mm.

BOE (40% NH ₄ F: 50% HF = 20: 1) solution and Al etchant (H ₃ PO ₄ : CH ₃ COOH: HNO ₃ : H ₂ ), which is an etching prescription solution of SiNx and Al-Nb in the prior art O = 65: 5: 5: 25) and the respective specimens were immersed in the composition solutions A and B according to the present invention for a certain time. The results are shown in the table below.

Etching target film Composition Treatment temperature (℃) Processing time (sec) SiNx A 25 120 B 25 90 BOE 25 180 Al-Nb A 25 300 B 25 240 Al etchant 25 300

As can be seen from the above results, not only the treatment time of the etching solution according to the present invention was short, but also the treatment with the composition B was excellent in uniformity over the entire substrate.

Example 5-3

<Process Experiment of Indium Tin Oxide (ITO) Thin Film on LCD Substrate>

A 50 mm x 50 mm x 0.7 mm specimen was prepared in which an ITO thin film was laminated on the LCD substrate with a thickness of 400 mm 3. ITO etchant in the prior art includes _{three types of} aqua regia (HCl + HNO ₃ + H ₂ O), ferric chloride hydrochloric acid (FeCl ₃ + HCl), HBr or HI system.

Each specimen was sprayed for a period of time with an aqua regia (HCl: HNO ₃ : H ₂ O = 18.5: 4.5: 77), which is an etching prescription of ITO, and the compositions A and B according to the present invention.

The results are shown in the table below.

Composition Treatment temperature (℃) Processing time (sec) Remarks A 35 180 No Hume occurrence B 35 120 " aqua regia 35 120 Cl ₂ and NOx generation

As described above, in the composition according to the present invention, which is completely different from the composition in the prior art, Hume was not generated and the ITO thin film was removed.

In particular, treatment with Composition B was excellent in uniformity over the entire substrate. It can be seen that the aqua regia solution has a low compositional reproducibility due to a large compositional variation due to the characteristics of the composition.

Example 6: Weight loss and hydrophilicity measurements on quartz plants

A tubular quartz specimen for wafer processing having a size of 5 mm × 5 mm × 3 mm was prepared and deposited for 10 minutes in Composition A and 15% hydrofluoric acid of the present invention to investigate the weight loss and hydrophilic state and to examine the presence of particles by visual inspection. the results are as follow.

Cleaning composition Processing time (min) Treatment temperature (℃) Weight loss (%) Hydrophilicity Check Particle Visual Inspection 15% HF 10 25 0.12 Hydrophilic OK Composition A 10 25 0.02 Hydrophilic OK

As can be seen from the table, while the composition of the present invention is significantly less weight loss, it can be seen that the existing cleaning solution, hydrofluoric acid is excessively etched. In other words, it can be seen that the composition according to the present invention can effectively remove contaminants adhering to the surface of the quartz facility in the manufacturing process and use process of the quartz facility, while avoiding excessive etching of the quartz base material. In addition, the weight is reduced by 1/6, it can be seen that the durability of the equipment is improved because the wear of the equipment is delayed.

According to the above, when a composition using a fluoride salt and a persulfate is used, not only a uniform reproducibility can be obtained during cleaning on the substrate, but also only a portion to be etched by fine etching can be significantly removed, thereby improving surface roughness.

Claims (6)

In cleaning and etching the SiO ₂ surface on the substrate, a) 0.1-50% by weight, based on the total amount of the total composition, b) 0.1-50% by weight of persulfate based on the total amount of the total composition As an optional component, it is made by adding one or more from the group consisting of surfactants, accelerators and inhibitors, If surfactant is selected, 0.01-5% by weight, based on the weight of the total composition, Cleaning and etching compositions for electronic display devices, quartz equipment and semiconductor substrates, comprising adding 0.01-10% by weight of the inhibitor component and 0.5-20% by weight of the accelerator component. The method of claim 1, wherein a) 0.4-12% by weight of a fluoride salt based on the total amount of the total composition, b) 6-18% by weight persulfate, based on the total amount of the total composition and As an optional component, it comprises one or more from the group consisting of surfactants, accelerators and inhibitors, If a surfactant is selected, 0.02-3% by weight based on the weight of the total composition, A composition comprising adding 0.1-3% by weight of the inhibitor component and 1-10% by weight of the accelerator component. The method of claim 1, wherein the fluoride salts are acidic ammonium fluoride (NH ₄ HF ₂ ), ammonium fluoride (NH ₄ F), sodium fluoride (NaF), acidic potassium fluoride (KHF ₂ ), acidic sodium fluoride (NaHF ₂ ), A composition characterized in that it is selected from the group consisting of barium fluoride (BaF ₂ ), potassium fluoride (KF) and ammonium borohydride (NH ₄ BF ₄ ) According to claim 1, wherein the persulfate is a group consisting of sodium persulfate (Na ₂ S ₂ O ₈ ), ammonium persulfate ((NH ₄ ) ₂ S ₂ O ₈ ) and potassium persulfate (K ₂ S ₂ O ₈ ) Compositions selected from The composition of claim 1, wherein the inhibitor is selected from amines and amides. The composition of claim 1, wherein the promoter is selected from sulfuric acid, phosphoric acid and acetic acid.