KR20210020378A - Method for wet two-step surface texturing of silicon wafer produced by kerfless - Google Patents

Abstract

The present invention relates to a wet two-step surface texturing method of a silicon wafer. In a method for forming a texture on a surface of the silicon wafer manufactured by a Kerfless method, the wet two-step surface texturing method of the silicon wafer comprises: a cleaning step of cleaning a surface of a silicon wafer through a wet cleaning solution; a pretreatment step of immersing the cleaned silicon wafer in a first acid solution to form a hole in the surface; a cleaning step of cleaning the surface of the silicon wafer on which the hole is formed through deionized water; and an etching step of immersing the cleaned silicon wafer in a second acid solution to form a texture on the surface.

Description

Wet two-stage surface texture method of silicon wafer manufactured in Kerfless method {METHOD FOR WET TWO-STEP SURFACE TEXTURING OF SILICON WAFER PRODUCED BY KERFLESS}

The present invention relates to a wet two-stage surface texture method of a silicon wafer manufactured in a Kerfless method.

Crystalline silicon solar cells occupy 90% of the global solar cell market, and the global solar cell market continues to develop at a very rapid pace over the past 10 years.

In addition, among wafer materials that account for 60% of the manufacturing cost in manufacturing a crystalline silicon solar cell, polycrystalline silicon wafers are attracting attention in the future solar cell market at a lower cost of 30-50% compared to single crystal silicon wafers.

In addition, many studies are being conducted to manufacture low-cost, high-quality crystalline silicon solar cells in line with the recent solar cell market trend. In particular, 4 steps are required to manufacture silicon wafers, and about 30 to 40% of cutting is required. Research on Kerfless and Saw Damage Free methods in which there is no waste of silicon material by replacing the casting method in which Kerf-loss occurs, and the step of the process is reduced is increasing.

Such, Kerfless and Saw Damage Free methods can reduce process costs by about 50% and energy savings of about 66% compared to the conventional casting method.

However, the technology as described above has the following problems.

In general, a solar cell needs to minimize reflection of incident light for efficient absorption of light energy, and for this purpose, a surface texturing process is performed or an antireflection film is deposited on the surface of a polycrystalline silicon wafer.

More specifically, in the case of polycrystalline silicon wafers, an anisotropic texturing method, which is a wet method using an acid solution for surface texturing, is being applied in the industry, and the anisotropic texturing method uses saw marks and saw damage generated in the casting method as seeds. To induce anisotropic etching on the surface of the polycrystalline silicon wafer.

However, since polycrystalline silicon wafers fabricated by Kerfless and Saw Damage Free methods do not have saw damage, there is a limitation in that surface texturing is impossible with a wet texturing method using an acid solution generally used in the industry.

In order to solve this problem, studies such as plasma etching and metal-catalyzed chemical etching, which are methods for texturing the surface of polycrystalline silicon wafers, are being conducted, but the plasma etching method has a problem of increasing process cost. In the case of metal catalyst etching, there is a problem in that wafer contamination and metal by-products must be removed.

Embodiments of the present invention have been proposed to solve the above problems, by using a simple wet process to form a hole that can serve as a seed for forming a texture on the surface of a polysilicon wafer and at the same time It is intended to provide a wet two-stage surface texture method capable of improving quality by etching existing defects.

In addition, it is intended to provide a wet two-stage surface texture method capable of high-quality surface texturing at low cost without complicated processes such as vacuum and metal catalysts.

In addition, it is intended to provide a wet two-step surface texture method that can be easily applied to a wafer of a larger scale than that of a general polycrystalline silicon wafer, and that uniform texturing is possible over the entire wafer surface.

The wet two-step surface texture method of a silicon wafer manufactured in a Kerfless method according to an embodiment of the present invention is a method of forming a texture on a surface of a silicon wafer manufactured in a Kerfless method, wherein the silicon wafer is formed by using a wet cleaning solution. A cleaning step of cleaning the surface; A pretreatment step of immersing the cleaned silicon wafer in a first acid solution to form holes in the surface thereof; And a washing step of cleaning the surface of the silicon wafer in which the holes are formed through deionized water, and an etching step of immersing the cleaned silicon wafer in a second acid solution to form a texture on the surface.

In addition, the cleaning step is characterized in that the wet cleaning solution is a mixed solution in which hydrofluoric acid and water are mixed in a ratio of 1:10-100.

In addition, in the pretreatment step, the first acid solution contains hydrofluoric acid having a concentration of 40 to 55%, nitric acid having a concentration of 65 to 75%, and acetic acid having a concentration of 90 to 99% in a ratio of 18-54:1-3:10-30. It is characterized in that it is a mixed solution.

In addition, the pretreatment step is characterized in that the cleaned silicon wafer is immersed in the first acid solution at room temperature for 20 to 40 seconds.

In addition, the pretreatment step is characterized in that the proportion of hydrofluoric acid in the first acid solution is 18 times higher than that of nitric acid.

In addition, the pretreatment step is characterized in that the hole is formed on the surface of the silicon wafer around a defect that is a region having a low activation energy required for an oxidation reaction.

In addition, the pretreatment step is characterized in that the hole is formed by etching silicon oxide formed by nitric acid by hydrofluoric acid.

In addition, the pretreatment step is characterized in that the hole has a deep and narrow pit shape, a central depth of 0.5 to 1.5 µm, and a diameter of 1 to 3 µm.

In addition, in the etching step, the second acid solution is a mixed solution in which hydrofluoric acid having a concentration of 40 to 55%, nitric acid having a concentration of 65 to 75%, and deionized water are mixed in a ratio of 1-3:6-18:7-21. It is characterized by that.

In addition, in the etching step, the cleaned silicon wafer is immersed in the second acid solution at a temperature of 5 to 15 degrees Celsius for 1 to 10 minutes.

The wet two-stage surface texture method according to the embodiments of the present invention uses a simple wet process to form a hole that can serve as a seed for forming a texture on the surface of a polycrystalline silicon wafer and at the same time, defects present on the wafer surface There is an effect that can improve the quality by etching.

In addition, high quality surface texturing is possible at low cost without complicated processes such as vacuum and metal catalysts.

In addition, it can be easily applied to wafers of a larger scale than general polycrystalline silicon wafers, and uniform texturing over the entire wafer surface is possible.

1 is a flow chart illustrating a wet two-step surface texture method of a silicon wafer manufactured in a Kerfless method according to an embodiment of the present invention.
2 is a process diagram illustrating a process of a wet two-stage surface texture method of a silicon wafer manufactured in a Kerfless method according to an embodiment of the present invention.
3 is an SEM image showing the surface of a silicon wafer manufactured by Kerfless and Saw Damage Free methods.
4 is a SEM image showing the surface of a polycrystalline silicon wafer after a pretreatment step of forming a hole in the wafer surface according to an embodiment of the present invention.
5 is a 3D AFM image showing the surface of a polycrystalline silicon wafer after a pretreatment step of forming a hole in the wafer surface according to an embodiment of the present invention.
6 is a SEM image showing the surface of a silicon wafer after an etching step of forming a texture on the wafer surface according to an embodiment of the present invention.
7 is a graph showing a surface reflectance of a silicon wafer after an etching step according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. The embodiments of the present invention may be modified in various forms, and the scope of the present invention should not be construed as being limited to the following embodiments. This embodiment is provided to more completely describe the present invention to those with average knowledge in the art. Therefore, the shape of the element in the drawings has been exaggerated to emphasize a clearer description.

The configuration of the invention for clarifying the solution to the problem to be solved by the present invention will be described in detail with reference to the accompanying drawings based on a preferred embodiment of the present invention, but the same in assigning reference numerals to the components of the drawings For the components, even if they are on different drawings, the same reference numerals are given, and it should be noted in advance that components of other drawings may be referred to when necessary when describing the drawings.

1 is a flow chart showing a wet two-stage surface texture method of a silicon wafer manufactured in a Kerfless method according to an embodiment of the present invention, and FIG. 2 is a view of a silicon wafer manufactured in a Kerfless method according to an embodiment of the present invention. It is a flow chart for explaining the process of the wet two-stage surface texture method.

Typical polycrystalline silicon wafer manufacturing methods are classified into CZ (Czochralski) method, FZ (Floating Zone Melting) method, Bridgman method, and Casting method.

The casting method is a method of naturally solidifying a molten silicon metal by pouring it into a crucible and slowly cooling it to produce a polycrystalline silicon ingot of a random shape.

Thereafter, the prepared polycrystalline silicon ingot is cut to an appropriate size, and the cut polycrystalline silicon ingot is thinly sliced with a jigsaw.

In contrast, the Kerfless and Saw damage free methods can produce a polycrystalline silicon wafer in the form of thin pieces of 180 to 200 µm thick without a Sawing process by melting high-purity silicon raw stones, thereby reducing waste of raw silicon materials and As it is reduced, polycrystalline silicon wafers can be manufactured at low process cost.

However, since the surface of a polycrystalline silicon wafer manufactured by Kerfless and Saw Damage Free method does not have saw mark and saw damage generated in the process of thinly slicing with a jigsaw in the conventional casting method, it is wetted using an acid solution used in general industries. There is a problem in that it is difficult to form a texture for absorbing light by the texturing method.

Accordingly, in the following, a wet two-step surface texture method capable of forming a texture using an acid solution on the surface of a silicon wafer manufactured in a Kerfless method according to an embodiment of the present invention is provided.

Referring to FIG. 1, the wet two-step surface texture method (S10) of a silicon wafer manufactured in a Kerfless method according to an embodiment of the present invention is a cleaning step (S100) of cleaning the surface of a silicon wafer using a wet cleaning solution. , Pre-treatment step (S200) of immersing the cleaned silicon wafer in a first acid solution to form holes on the surface (S200), cleaning step (S300) of cleaning the surface of the silicon wafer having holes formed using deionized water (S300), and the cleaned silicon wafer. It includes an etching step of immersing in a second acid solution to form a texture on the surface.

First, the surface of a silicon wafer manufactured by Kerfless and Saw Damage Free method is cleaned using a wet cleaning solution (S100).

In addition, in the cleaning step (S100) _{, a wet cleaning solution, which is a mixed solution in which hydrofluoric acid (HF) and water (H 2} O) are mixed in a ratio of 1:10-100 may be used.

In addition, the cleaning step (S100) is preferably washed at room temperature for 20 to 60 seconds using the wet cleaning solution.

In addition, in the cleaning step (S100), a wet cleaning solution containing hydrofluoric acid (HF) can effectively remove metal contaminants contained in the oxide film, but noble metals such as copper (Cu), silver (Ag), and gold (Au) Since silver is difficult to remove, hydrogen peroxide (H ₂ O ₂ ) may be further added to the wet cleaning solution.

As a result, impurities such as metals in the oxide film and the natural oxide film formed on the surface of the silicon wafer may be simultaneously removed by using hydrofluoric acid (HF).

When the step S100 is finished, the cleaned silicon wafer is immersed in the first acid solution to form holes in the surface (S200).

In this case, the first acid solution may contain at least one acid, at least one surfactant, a solvent, and a catalyst, essentially or selectively, or consist of them.

According to an embodiment of the present invention, the first acid solution contains 40 to 55% hydrofluoric acid (HF), 65 to 75% nitric acid (HNO ₃ ) and 90 to 99% acetic acid (CH ₃ COOH). It is a mixed solution mixed in a ratio of 18-54:1-3:10-30, and is not limited thereto as long as it can form holes on the surface of a silicon wafer.

That is, according to an embodiment of the present invention, it is preferable that the ratio of hydrofluoric acid (HF) in the first acid solution of the pretreatment step (S200) is 18 times higher than _{that of nitric acid (HNO 3 ).}

In addition, in the pretreatment step (S200), the cleaned silicon wafer is immersed in the first acid solution at room temperature for 20 to 40 seconds.

In addition, the pretreatment step S200 may be performed at a temperature lower than room temperature, and more specifically, the cleaned silicon wafer may be immersed for 40 to 140 seconds at a temperature condition of 10 to 20 degrees Celsius.

According to an embodiment of the present invention, nitric acid (HNO ₃ ) reacts with silicon atoms to form an oxide layer on the surface of a silicon wafer, and hydrofluoric acid (HF) etch the generated oxide layer.

In this case, nitric acid (HNO _{3 ) may cause silicon oxide (SiO 2} ) to be formed around defects of a silicon crystal structure formed by silicon atoms on the surface of the silicon wafer. The defect acts as a site where the formation of silicon oxide and the etching reaction can easily occur because the activation energy required for the oxidation reaction is low due to the incomplete crystal structure.

In addition, a material that generates an oxide layer on the surface of the silicon wafer is not limited to _{nitric acid (HNO 3 ).} For example, hydrogen peroxide (H ₂ O ₂ ) and hexavalent chromium (CrO ₃ ) may be used in place of nitric acid (HNO _{3 ).}

Thereafter, hydrofluoric acid (HF) may react with the _{formed silicon oxide (SiO 2} ) to generate _{silicon tetrafluoride (SiF 4} ), silicic fluoride (H ₂ SiF ₆ ), and water (H _{2 O).}

That is, since hydrofluoric acid (HF) _{etch the formed silicon oxide (SiO 2} ), if a first acid solution containing hydrofluoric acid (HF) in a higher ratio than nitric acid (HNO _{3) is used, the silicon in the pretreatment step (S200)} Holes in the form of narrow and deep pits are formed on the wafer surface.

According to an embodiment of the present invention, acetic acid (CH ₃ COOH) is an etching method in which the hydrofluoric acid (HF) and nitric acid (HNO ₃ ) form silicon oxide (SiO ₂ ), and the formed silicon oxide (SiO ₂ ) is etched. You can make the reaction proceed quickly.

More specifically, the acetic acid (CH ₃ COOH) activates a wetting phenomenon between the silicon wafer and the first acid solution, thereby preventing bubbles from being formed on the surface of the silicon wafer. That is, the first acid solution wets the silicon wafer surface well.

Here, the wetting phenomenon means a phenomenon in which a new solid/liquid interface is created instead of the solid/gas surface.

Accordingly, the acetic acid (CH ₃ COOH) can help the etching reaction of forming a hole in the silicon wafer to sufficiently occur in a short time condition of 40 seconds or less even when the pretreatment step (S200) is performed at room temperature, It helps to form dense and uniform holes on the silicon wafer surface.

According to an embodiment of the present invention, in the pretreatment step (S200), a silicon wafer is immersed in a first acid solution combined with a strong acid for a certain period of time, so that a defect (a region having a low activation energy required for an oxidation reaction) on the surface of the silicon wafer In Defect), oxide formation and etching reaction proceed, and narrow and deep hole-shaped holes are formed.

In addition, the holes may be formed finely and uniformly on the surface of the silicon wafer.

When the step S200 is finished, the surface of the silicon wafer in which the holes are formed is cleaned using deionized water (S300).

In addition, the washing step (S300) may be performed for 10 minutes at room temperature, and may sometimes be cleaned using ultrasonic waves.

When the step S300 is finished, the cleaned silicon wafer is immersed in the second acid solution and etched to form a texture on the surface (S400).

In this case, the second acid solution may contain one or more acids, one or more surfactants, and a solvent, essentially or selectively, or consist of them.

According to an embodiment of the present invention, the second acid solution has a concentration of 40 to 55% of hydrofluoric acid (HF), a concentration of 65 to 75% of nitric acid (HNO ₃ ) and deionized water (DI Water) of 1-3:6- It is a mixed solution mixed in a ratio of 18:7-21, and is not limited thereto as long as it can form a texture on the surface of a silicon wafer.

That is, according to an embodiment of the present invention, _{it is preferable that the ratio of nitric acid (HNO 3} ) in the second acid solution of the etching step (S200) is 6 times higher than that of hydrofluoric acid (HF).

In addition, in the etching step (S400), the cleaned silicon wafer is immersed in the second acid solution in a temperature condition of 5 to 15 degrees Celsius for 1 to 10 minutes.

As in the pretreatment step S200, nitric acid (HNO ₃ ) reacts with silicon atoms to generate an oxide layer on the surface of the silicon wafer, and then hydrofluoric acid (HF) may etch the oxide layer.

As a result, in the etching step (S400), an uneven texture may be formed on the surface of the silicon wafer, and since the silicon wafer surface is isotropically etched unlike an etching reaction using a general basic and acidic solution, a random crystal plane is exposed. Texturing is performed in the form.

That is, the etching reaction of the second acid solution in the etching step S400 may induce isotropic etching, and the texture may be formed in a random isotropic shape to have a round shape.

In addition, in _{the etching step (S400) in which the ratio of nitric acid (HNO 3} ) is higher than that of hydrofluoric acid (HF), a narrow and deep pit-shaped hole previously formed on the surface of the silicon wafer expands widely in the horizontal direction to form a texture. It is possible to manufacture a silicon wafer with excellent surface reflectivity that can be utilized for

Accordingly, in the wet two-step surface texture method (S10) of a silicon wafer manufactured in a Kerfless method according to an embodiment of the present invention, the ratio of hydrofluoric acid (HF) in the pretreatment step (S200) is higher than _{nitric acid (HNO 3 ).} By using acetic acid (CH ₃ COOH) as a catalyst, holes in the form of narrow and deep pits that can be used as seeds in forming a texture having a reflectance suitable for solar cells can be formed.

In addition, in an embodiment of the present invention, after forming a narrow and long hole that can be used as a seed by increasing the HF ratio in the pretreatment step (S200), nitric acid (HNO ₃ ) is used in the etching step (S400). By increasing the ratio and processing the hole in the form of a narrow and deep pit that has already been formed so that it can be widely expanded in the horizontal direction, a texture having a reflectance suitable for a solar cell can be finally formed.

As shown in FIG. 2, when the silicon wafer 100 is immersed in the first acid solution, holes 200 in the form of pits may be formed on the surface of the silicon wafer 100.

Thereafter, the silicon wafer 100 on which the holes 200 are formed is immersed in the second acid solution to form the texture 300 on the surface of the silicon wafer 100.

At this time, the hole 200 serves as a seed that induces the formation of the texture 300, such as the saw mark and saw damage described above, and accordingly, an isotropic etching phenomenon due to an acid solution may occur.

That is, it is possible to effectively form the texture 300 on the surface of a silicon wafer manufactured in Kerfless and Saw Damage free methods using an acid solution used in a general industry.

3 is an SEM image showing the surface of a silicon wafer manufactured by Kerfless and Saw Damage Free methods, and FIG. 4 is an SEM showing the surface of the silicon wafer after a pretreatment step of forming a hole in the wafer surface according to an embodiment of the present invention. 5 is a 3D AFM image showing the surface of a silicon wafer after a pretreatment step of forming a hole on the wafer surface according to an embodiment of the present invention, and FIG. 6 is a texture on the wafer surface according to an embodiment of the present invention. Is an SEM image showing the surface of the silicon wafer after the etching step of forming a, and FIG. 7 is a graph showing the surface reflectance of the silicon wafer after the etching step according to an embodiment of the present invention.

Referring to FIG. 3, FIG. 3 is an electron microscope image showing the surface of a silicon wafer manufactured by Kerfless and Saw Damage Free methods, and is smoother than the surface of a polycrystalline silicon wafer manufactured by the casting method, which is a general wafer manufacturing method. You can see that it has a state.

That is, since the Kerfless and Saw Damage Free methods do not include a process step of thinly slicing the cut polycrystalline silicon ingot, unlike the casting method, saw marks and saw-damage hardly appear on the silicon wafer surface.

4 and 5, according to an embodiment of the present invention, HF at a concentration of 49%, HNO _{3 at a concentration of 70%, and CH 3} COOH at a concentration of 99% are mixed in a ratio of 36:2:20 It can be seen that fine holes are uniformly and densely formed on the surface of the silicon wafer immersed in the first acid solution, which is the mixed solution, at 25 degrees Celsius for 30 seconds.

In addition, in FIG. 5, it can be seen that the hole has a narrow and deep pit shape, has a central depth of 0.5 to 1.5 µm, and a diameter of 1 to 3 µm.

6, after forming a hole on the surface of a silicon wafer, according to an embodiment of the present invention, HF having a concentration of 49%, HNO _{3 having a} concentration of 70%, and DI Water of 1:6:7 It can be seen that the uneven texture is uniformly formed on the surface of the silicon wafer, which was immersed in the second acid solution, which is a melting solution mixed at a ratio, at a temperature of 8 degrees Celsius for 3 minutes.

Referring to FIG. 7, Bare is the surface reflectance of a silicon wafer manufactured by Kerfless and Saw Damage Free methods, and Normal wet is the surface reflectance of a silicon wafer manufactured by Kerfless and Saw Damage Free methods subjected to commonly used wet etching treatment. And Double wet shows the surface reflectance of a silicon wafer fabricated in a Kerfless and Saw Damage Free method etched using a wet two-step surface texture method (S10) according to an embodiment of the present invention. The horizontal axis of the graph is the wavelength expressed in nanometers, and the vertical axis is the% surface reflectance.

As shown in the graph of FIG. 7, the silicon wafer etched by a wet two-stage surface texture method including a pretreatment step (S200) for forming a hole and an etching step (S400) for forming a texture of the present invention is dense and wide on the surface. It can be seen that the expanded texture is uniformly formed, so that the surface reflectance of the incident light is the lowest.

In addition, it can be seen that the silicon wafer subjected to the wet two-step surface texture etching process obtains a reflectance of approximately 27% as a surface reflectance value, which is similar to the surface reflectance obtained by wet texturing on a silicon wafer manufactured by the casting method. to be.

That is, the silicon wafer having holes formed on the surface through the pretreatment step (S200) of the present invention does not go through the process of forming a hole, and exhibits a lower reflectance than that of the etching treatment, so that the pretreatment step (S200) of forming the hole is low. It can be seen that it is an important variable in obtaining reflectance.

Accordingly, according to an embodiment of the present invention as described above, after forming a hole in the surface of the silicon wafer using the pretreatment step (S200), the wet two-step surface texture method of etching the surface of the silicon wafer in which the hole is formed is simple. Even with a wet process, the reflectance for incident light can be effectively reduced.

In addition, since holes can be formed only by immersing a silicon wafer in an acid solution in the pretreatment step, it can be easily applied to wafers of a larger scale than general polycrystalline silicon wafers, and uniform texturing over the entire wafer surface is possible. .

The detailed description above is illustrative of the present invention. In addition, the above description shows and describes preferred embodiments of the present invention, and the present invention can be used in various other combinations, modifications and environments. That is, changes or modifications may be made within the scope of the concept of the invention disclosed in the present specification, the scope equivalent to the disclosed contents, and/or the skill or knowledge of the art. The above-described embodiments describe the best state for implementing the technical idea of the present invention, and various changes required in the specific application fields and uses of the present invention are possible. Therefore, the detailed description of the invention is not intended to limit the invention to the disclosed embodiment. In addition, the appended claims should be construed as including other embodiments.

100: silicon wafer
200: Hall
300: texture

Claims (10)

In the method of forming a texture on the surface of a silicon wafer manufactured in a Kerfless method,
A cleaning step of cleaning the surface of the silicon wafer through a wet cleaning solution;
A pretreatment step of immersing the cleaned silicon wafer in a first acid solution to form holes in the surface thereof;
A cleaning step of cleaning the surface of the silicon wafer in which the hole is formed through deionized water; And
A wet two-step surface texture method of a silicon wafer comprising an etching step of immersing the cleaned silicon wafer in a second acid solution to form a texture on the surface.
The method of claim 1,
The cleaning step is:
The wet two-step surface texture method of a silicon wafer, wherein the wet cleaning solution is a mixed solution in which hydrofluoric acid and water are mixed in a ratio of 1:10-100.
The method of claim 1,
The pretreatment step is:
Silicone, a mixed solution in which the first acid solution is mixed with hydrofluoric acid having a concentration of 40 to 55%, nitric acid having a concentration of 65 to 75%, and acetic acid having a concentration of 90 to 99% at a ratio of 18-54:1-3:10-30 Wet two-step surface texture method of wafers.
The method of claim 1,
The pretreatment step is:
A wet two-step surface texture method for a silicon wafer, wherein the cleaned silicon wafer is immersed in the first acid solution at room temperature for 20 to 40 seconds.
The method of claim 1,
The pretreatment step is:
A wet two-stage surface texture method of a silicon wafer in which the ratio of hydrofluoric acid in the first acid solution is 18 times higher than that of nitric acid.
The method of claim 1,
The pretreatment step is:
A wet two-stage surface texture method for a silicon wafer, wherein the hole is formed around a defect in the surface of the silicon wafer, a region having a low activation energy required for an oxidation reaction.
The method of claim 6,
The pretreatment step is:
A wet two-step surface texture method of a silicon wafer, wherein the hole is formed by etching silicon oxide formed by nitric acid by hydrofluoric acid.
The method of claim 7,
The pretreatment step is:
A wet two-stage surface texture method of a silicon wafer, wherein the hole has a deep and narrow pit shape, a central depth of 0.5 to 1.5 µm, and a diameter of 1 to 3 µm.
The method of claim 1,
The etching step is:
The second acid solution is a mixed solution in which hydrofluoric acid having a concentration of 40 to 55%, nitric acid having a concentration of 65 to 75%, and deionized water is mixed in a ratio of 1-3:6-18:7-21. Surface texture method.
The method of claim 1,
The etching step is:
A wet two-step surface texture method for a silicon wafer, wherein the cleaned silicon wafer is immersed in the second acid solution at a temperature condition of 5 to 15 degrees Celsius for 1 to 10 minutes.

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