KR101052059B1

KR101052059B1 - Surface processing method of silicon substrate for solar cell, and manufacturing method of solar cell

Info

Publication number: KR101052059B1
Application number: KR1020100092130A
Authority: KR
Inventors: 김병준
Original assignee: 김병준
Priority date: 2010-04-14
Filing date: 2010-09-17
Publication date: 2011-07-27
Also published as: CN102222723A; KR20110115068A; CN102222723B; TW201135956A; CN102222721B; CN102222719B; KR101630802B1; TWI451586B; CN102222721A; KR20110115071A; CN102222719A

Abstract

PURPOSE: A method for surface-processing a crystalline silicon substrate for a solar cell and a method for manufacturing a solar cell are provided to reduce remarkably a reflectance of a substrate for a solar cell and to improve the efficiency of the solar cell by forming a second fine concavo-convex part through a second surface processing step. CONSTITUTION: A first surface processing step is to form a plurality of first concavo-convex parts on an outer surface of a substrate by etching a sliced polycrystalline silicon substrate in a polycrystalline silicon ingot. A second surface processing step is to form the second concavo-convex parts smaller the first concavo-convex parts by dry-etching a surface for forming an anti-reflective layer of the outer surface of the substrate on which the first concavo-convex parts are formed through the first surface processing step.

Description

Surface treatment method of silicon substrate for solar cell and manufacturing method of solar cell {Surface processing method of silicon substrate for solar cell, and manufacturing method of solar cell}

The present invention relates to a solar cell, and more particularly, to a surface treatment method and a solar cell manufacturing method of a crystalline silicon substrate for solar cells for treating the surface of the crystalline silicon substrate.

A solar cell refers to a cell that generates electromotive force by applying a photovoltaic effect, which is one of photoelectric effects.

Solar cells are classified into silicon based solar cells, compound semiconductor solar cells, compounds or stacked solar cells according to the material of the substrate. Here, silicon-based solar cells are further classified into crystalline silicon solar cells such as monocrystalline silicon and polycrystalline silicon and amorphous silicon solar cells.

The efficiency of the solar cell is determined by various variables such as the reflectance of the substrate and can be maximized by minimizing the reflection of the light on the surface to be received.

Meanwhile, various methods for minimizing the reflectance of light have been studied in the crystalline silicon solar cell field having low manufacturing cost to improve the efficiency of the solar cell.

An object of the present invention is to provide a surface treatment method and a method for manufacturing a solar cell of the crystalline silicon substrate for solar cells that can minimize the reflection of light on the surface of the crystalline silicon substrate for solar cells.

The present invention was created in order to achieve the object of the present invention as described above, the present invention by etching the crystalline silicon substrate sliced in the crystalline silicon ingot with an acidic aqueous solution to form a plurality of first irregularities on the outer surface of the substrate Surface treatment step; And a second surface treatment step of forming a second unevenness having a smaller size than the first unevenness by dry etching a surface on which an antireflection film is to be formed among the outer surfaces of the substrate on which the first unevennesses are formed through the first surface treatment step. Disclosed is a surface treatment method of a crystalline silicon substrate for a solar cell.

In the first surface treatment step, the acidic aqueous solution may include HNO ₃ and HF, and the acidic aqueous solution may be mixed in a ratio in which a substantial mass ratio of HNO ₃ and HF in the aqueous solution is 1: 1 to 5.5: 1.

The first surface treatment step is performed by an in-line method carried out while the substrate is transferred by a roller to a reservoir containing an acidic aqueous solution, and etching may be performed at a temperature of 6 ° C. to 10 ° C. for 1 minute to 10 minutes.

The first surface treatment step is performed by a dipping method in which an etching is performed by immersing in a storage tank containing an acidic aqueous solution, and etching may be performed at a temperature of 6 ° C. to 10 ° C. for 20 minutes.

The first surface treatment step may further include a substrate damage treatment step of removing the damage of the crystalline silicon substrate sliced in the crystalline silicon ingot with an acidic aqueous solution or an alkaline aqueous solution.

After the first surface treatment step, a first cleaning step of removing impurities generated in the first surface treatment step, a sub-etch process of partially etching the porous silicon dioxide remaining on the outer surface of the substrate using an alkali compound; A second cleaning step of removing impurities remaining on an outer surface of the substrate after the sub-etching step; The method may further include a drying process of drying the substrate after the second cleaning process.

After the first surface treatment step and before the second surface treatment step or after the second surface treatment step, an outer surface of the outer surface of the substrate on which the plurality of first unevennesses are formed in the first surface treatment step is opposite to the surface on which the antireflection film is to be formed. The back surface of the phosphorus may further include a back surface irregularity removing step of removing the first surface irregularities formed on the back surface by etching.

The second unevenness may have a substantially triangular cross section, and a side of the first unevenness may be shorter than an opposite side thereof.

The crystalline silicon substrate may be a single crystal silicon substrate or a polycrystalline silicon substrate.

After the first surface treatment step, the crystalline silicon substrate is formed of the surface of the surface etched in the first surface treatment step when the area of the surface on which the antireflection film is to be formed is completely planar. The area ratio of actual surface area to ideal area may be comprised between 1.2 and 3.2.

The present invention also discloses a method of manufacturing a solar cell comprising the surface treatment method of a crystalline silicon substrate for solar cells as described above.

The surface treatment method and the solar cell manufacturing method of the crystalline silicon substrate for solar cells according to the present invention is first formed by the first surface treatment step by wet, and by dry, that is by the second surface treatment step by dry etching By forming the fine irregularities as the secondary, the reflectance of the solar cell substrate is remarkably reduced, thereby improving the efficiency of the solar cell.

In particular, the first surface treatment step may be performed by using an acidic aqueous solution that is performed at a low temperature rather than using an alkaline aqueous solution that is performed at a high temperature, thereby improving the reproducibility and reliability of the process.

In addition, the area ratio between the actual surface area and the abnormal area of the crystalline silicon substrate etched in the first surface treatment step is 1.2 to 3.2, thereby maximizing the reduction in reflectance due to the surface treatment.

In addition, the surface treatment method and the solar cell manufacturing method of the crystalline silicon substrate for solar cells according to the present invention includes a first surface treatment step of forming the irregularities by wet can shorten the process time by dry etching for forming fine roughness There is an advantage to that.

In addition, the surface treatment method and the solar cell manufacturing method of the crystalline silicon substrate for solar cells according to the present invention includes a first surface treatment step of forming irregularities by wet etching the plurality of substrates in the second surface treatment step by dry etching If there is an advantage that can improve the color difference (color difference) of the substrate located on the edge side.

1 is a cross-sectional view showing the structure of a solar cell.
FIG. 2 is a process chart showing the solar cell manufacturing method of FIG. 1.
3 is a process chart showing a surface treatment method of a crystalline silicon substrate for a solar cell according to the present invention.
4A is a partial cross-sectional view showing a substrate that is first surface-treated by the first surface treatment step of the surface treatment method of the substrate according to FIG. 3, and FIGS. 4B and 4C show an area ratio of less than 1.2 and 3.2 after the first substrate treatment, respectively. Some cross-sectional views showing the above case.
5 is a conceptual view illustrating a state in which irregularities are formed by the surface treatment method of the substrate according to FIG. 3.
6 is a partial cross-sectional view showing the substrate after the first surface treatment step and the second surface treatment step by the surface treatment method of the substrate according to the present invention.

Hereinafter, a surface treatment method of a crystalline silicon substrate for a solar cell according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view showing the structure of a solar cell, Figure 2 is a process chart showing a manufacturing method of the solar cell of FIG.

As an example of the solar cell according to the present invention, as shown in FIG. 1, the upper surface of the substrate 1 having the pn junction structure and the substrate 1 receiving light, that is, the light receiving surface (hereinafter, referred to as a “surface”). ) And a bottom electrode (2) and a back electrode (3) formed on the bottom surface (hereinafter referred to as the 'back'), and the anti-reflection film (4) formed on the surface of the substrate (1).

Here, the substrate 1 has a crystalline silicon material, more preferably a polycrystalline silicon material. In addition, in order to increase the light receiving area of the solar cell, an electrode may be formed only on the back side of the light receiving surface.

In the method of manufacturing the solar cell as described above, as illustrated in FIG. 2, a substrate processing step (S10) of processing a silicon substrate 1 by slicing from a silicon ingot to a device such as a wire saw. And, after the substrate processing step (S10) and the surface treatment step (S20) for forming the irregularities on the surface of the silicon substrate (1); A doping step (S30) of forming a p-n junction structure after the surface treatment step (S20); An anti-reflection film forming step (S40) of forming an anti-reflection film 4 on the surface of the substrate 1 after the doping step (S30); And an electrode forming step S50 for forming the electrodes 2 and 3 on the front and back surfaces of the substrate 1.

Here, the electrode forming step (S50) may be performed before the doping step (S30), depending on the manufacturing method of the solar cell, the process sequence may vary. In addition, the substrate processing step S10 may be performed separately or as in subsequent steps including the surface treatment step S20.

The method for manufacturing a solar cell including the above steps has various methods for each step. For convenience, a detailed description thereof will be omitted and the surface treatment method of the crystalline silicon substrate for a solar cell according to the present invention in connection with the surface treatment step (S20). This will be described in detail.

3 is a process chart showing a surface treatment method of a crystalline silicon substrate for a solar cell according to the present invention.

As shown in FIG. 3, the surface treatment method of the crystalline silicon substrate for a solar cell according to the present invention includes etching a crystalline silicon substrate 1 sliced from a crystalline silicon ingot with an acidic aqueous solution to form a plurality of substrates on the outer surface of the substrate 1. A first surface treatment step S210 for forming one unevenness 10; Through the first surface treatment step (S210), the surface of the substrate 1 on which the anti-reflection film 4 is to be formed is dry-etched on the outer surface of the substrate 1 on which the plurality of first unevennesses 10 are formed. It comprises a second surface treatment step (S230) to form a).

The first surface treatment step (S210) is a step of forming the first unevenness 10 by etching the outer surface of the crystalline silicon substrate 1 sliced from the crystalline silicon ingot with an acidic aqueous solution. In particular, the first surface treatment step S210 is intended to form a plurality of first unevennesses 10 as shown in FIG. 4A on the outer surface of the substrate 1.

In this case, when the acidic aqueous solution is used in the first surface treatment step (S210), it is possible to secure a lower reflectance on the surface of the substrate 1 on which the anti-reflection film 4 is to be formed than to use an alkaline aqueous solution, so that the amount of light received is Increase the performance of the solar cell can be improved.

In addition, when the alkaline aqueous solution is used in the first surface treatment step (S210), the dependency on the material of the substrate 1 is large. When the acidic aqueous solution is used, the dependency on the material of the substrate 1 may be reduced.

In addition, in the first surface treatment step S210, the first unevenness 10 may be formed only on the light receiving surface, that is, the surface of the substrate 1. In order to prevent this from being formed, a process for preventing the formation of the first unevenness on the back surface of the substrate 1 may be performed (mask forming step).

As the acidic aqueous solution used in the first surface treatment step (S210), an aqueous solution containing HNO ₃ and HF may be used, and the mass ratio and concentration thereof are determined in consideration of an etching temperature, an etching depth, and the like.

It is preferable that the ratio of the substantial mass ratio of HNO ₃ and HF in the aqueous solution of the acidic aqueous solution used in the first surface treatment step (S210) is 1: 1 to 5.5: 1. Herein, the acidic aqueous solution may further include a surface activator and a catalyst.

Meanwhile, the acidic aqueous solution may be an aqueous solution containing HNO ₃ , HF and CH ₃ COOH (or deionized water).

At this time, the etching depth (height) etched by the first surface treatment step (S210) is preferably 1㎛ ~ 10㎛.

The first surface treatment step (S210) as described above is immersed in an in-line method or a wet station containing an acidic aqueous solution in which etching is performed while the substrate 1 is transferred by a roller in a wet station containing an acidic aqueous solution. The etching may be performed by a dipping method in which etching is performed.

In this case, the first surface treatment step S210 may be performed while the substrate 1 is transferred by a roller, that is, performed in an in-line manner, and etching may be performed for 1 minute to 10 minutes at a temperature of 6 ° C to 10 ° C.

The first surface treatment step (S210) is performed by a dipping method in which etching is performed by immersing in a storage tank containing an acidic aqueous solution, and etching may be performed for 15 to 25 minutes at a temperature of 6 ° C to 10 ° C.

Meanwhile, the first surface treatment step (S210) may further include a subsequent process such as drying the surface of the substrate 1 after the etching is completed as it is performed by a wet solution such as an acidic aqueous solution.

That is, after the first surface treatment step S210, a first cleaning process S212 for removing impurities generated in the first surface treatment step S210, and porous silicon dioxide remaining on the outer surface of the substrate 1 may be performed. A sub-etching step (S213) for partially etching SiO ₂ ) using an alkali compound (NaOH or KOH), and a second cleaning step for removing impurities remaining on the outer surface of the substrate 1 after the sub-etching step (S213) ( S214); After the second cleaning process S214, a drying process S215 for drying the substrate 1 may be further included.

The first cleaning process S212 and the second cleaning process S214 are to remove impurities existing on the surface of the substrate 1, and are divided into one or a plurality of steps according to the type and characteristic of the impurities. Can be.

4A is a partial cross-sectional view showing a substrate that is first surface-treated by the first surface treatment step of the surface treatment method of the substrate according to FIG. 3, and FIGS. 4B and 4C show an area ratio of less than 1.2 and 3.2 after the first substrate treatment, respectively. Some cross-sectional views showing the above case. Figures 4a to 5 are shown roughly for the convenience of description, in practice there is a deviation in the depth of etching and the height, size, etc. of the top end, the shape of the cross-section and the actual shape is irregular and of course, of course.

On the other hand, the actual surface area (S _r ) of the surface on which the anti-reflection film (4) is to be formed among the outer surfaces of the substrate (1), which is etched in the first surface treatment step (S210) and the plurality of first unevennesses (10) are formed on the outer surface. ) And the area of the surface in which the surface is completely planar is an ideal area (S _i ), after the first surface treatment step (S210), the crystalline silicon substrate 1 is shown in FIGS. 4A and 5. Thus, the area ratio of the actual surface area (S _r) for at least the area (S _i) is preferably from 1.2 to 3.2.

When the area ratio is smaller than 1.2, as shown in FIG. 4B, the degree of generation of the unevenness 10 is small, and thus there is a problem in that the reduction in reflectance by the first surface treatment step S210 is not large.

In addition, when the area ratio is larger than 3.2, as shown in FIG. 4C, the reaction by the plasma is not large in the second surface treatment step (S230), which is a subsequent step, thereby reducing the surface treatment effect. Furthermore, when the area ratio is larger than 3.2, there is a problem that adversely affects subsequent processes, such as forming voids in the electrode forming step (S50), which is a subsequent process of the solar cell manufacturing method, to prevent diffusion of a metal material for forming electrodes.

Meanwhile, before the first surface treatment step S210, a substrate damage treatment step S11 of removing the damage generated during the slicing process from the crystalline silicon substrate 1 sliced from the crystalline silicon ingot with an acidic aqueous solution or an alkaline aqueous solution is further included. can do.

Herein, the acidic aqueous solution may be a mixed aqueous solution of HNO ₃ and HF, HNO ₃ , HF and CH ₃ COOH (or deionized water), and a mixed aqueous solution of HNO ₃ and HF may be used as 7: 1. Here, the ratio of H ₂ O in the mixed aqueous solution is determined by the choice of a person of ordinary skill in the art.

And the substrate damage treatment step (S11) is about 15 minutes to 25 minutes at about 80 ℃ ~ 90 ℃ in the case of alkaline aqueous solution. Here, the aqueous alkali solution is used NaOH or KOH, IPA (2-isopropyl-alcohol) may be further mixed.

In particular, in the substrate damage treatment step (S11), it is preferable to use an alkaline aqueous solution when the silicon substrate is a single crystal, and to use an acidic aqueous solution when the polycrystalline crystal is used.

Meanwhile, the substrate damage treatment step S11 may be included in the first surface treatment step S210 and integrated into one.

6 is a partial cross-sectional view showing the substrate after the first surface treatment step and the second surface treatment by the surface treatment method of the substrate according to the present invention.

The second surface treatment step S230 may dry-etch the surface on which the anti-reflection film 4 is to be formed on the outer surface of the crystalline silicon substrate 1 surface-treated in the first surface treatment step S210. 20) to form. In particular, the second surface treatment step S230 is for forming a plurality of second unevenness 20 as shown in FIG. 6 on the surface of the substrate 1. Here, the second unevenness 20 is minute irregularities smaller in size than the first unevenness 10. And the width and height of the first concave-convex 10 is approximately 2㎛ ~ 20㎛ and 1㎛ ~ 10㎛ (the first concave and convex 10 preferably has a hemispherical shape bar width corresponds to the diameter, the height is etched Depth may be a radius), and the second unevenness 20 may have a size of approximately 100 nm to 800 nm.

Dry etching performed in the second surface treatment step S230 may be performed by reactive ion etching (RIE) or inductively coupled plasma (ICP) using a vacuum chamber maintained at a predetermined vacuum pressure state. have.

The etching gas used for the dry etching may be Cl ₂ / CF ₄ / O ₂ , SF ₆ / O ₂ , CHF ₃ / SF ₆ / O ₂ , NF ₃ , F ₂ and mixtures thereof. At this time, the etching time is performed from about several seconds to several minutes.

When the dry etching is performed by the RIE, the dry etching by the RIE may be performed by installing a plate having a plurality of holes formed on the upper side of the substrate 1 in order to promote the formation of the second unevenness 20, which is fine irregularities. have.

In this case, the dry etching may be performed by transferring through a carrier on which the plurality of substrates 1 are loaded and loading them on a substrate support in a dry etching apparatus for dry etching.

Meanwhile, the surface of the substrate 1 after the surface treatment is performed by the second surface treatment step S230 as described above is illustrated in FIG. 6.

In the second surface treatment step S230, a plurality of second unevennesses 20 that are finer than the first unevenness 10 formed by the first surface treatment step S210 are formed on the surface of the substrate 1.

As shown in FIG. 6, the second unevenness 20 has a substantially triangular cross section, and a side of the first unevenness 10 that is directed toward the top of the first unevenness 10 is shorter than the opposite side thereof.

On the other hand, in the first surface treatment step S21, the substrate 1 has the first unevenness 10 formed on both the 'surface' on which the anti-reflection film 4 is formed, and the 'back' on the opposite side thereof, and the outer surface including the side surface. do.

However, although the plurality of first unevennesses 10 formed on the outer surface of the substrate 1 are effective in increasing the light receiving rate by reducing the reflection of light, the electrode forming step S50 is a subsequent process performed after the formation of the first unevenness 10. ), In particular, when manufacturing a high efficiency solar cell substrate that forms both electrodes on the back surface of the substrate 1, there is a problem of making electrode patterns difficult.

Accordingly, the first unevennesses 10 are preferably formed only on the light receiving surface, that is, the surface of the outer surface of the substrate 1, and the remaining surfaces need to be removed for the convenience of subsequent processes.

In particular, it is necessary to flatten the outer surface of the substrate 1 to facilitate the formation of the electrode pattern by using a screen mask to form the electrode on the outer surface of the substrate 1, and thus for the solar cell according to the present invention. The surface treatment method of the crystalline silicon substrate may include the first unevenness in the first surface treatment step S210 after the first surface treatment step S210 and before the second surface treatment step S230 or after the second surface treatment step S230. Removing the back surface unevenness (S220) of removing the first unevennesses 10 formed on the back surface by dry etching the back surface opposite to the surface on which the anti-reflection film 4 is to be formed among the outer surfaces of the substrate 1 on which the surfaces 10 are formed. It may further comprise.

The surface unevenness removing step (S220) is loaded into a dry etching apparatus so that the rear surface of the substrate 1 faces upward after the first surface treatment step, and then proceeds to planarization by performing 3um to 10um etching using RIE or IPC. Can be. At this time, the upper side of the substrate 1 may be performed by installing a plate formed with a plurality of holes as necessary.

As the etching gas used in the back surface unevenness step (S220), SF ₆ / O ₂ , SF ₆ / N ₂ and NF ₃ , CF ₄ , NF _3, ClF _3, F ₂ and mixtures thereof may be used. At this time, the etching time is about several seconds to several minutes.

By performing the back surface unevenness step S220 through dry etching as described above, the mask formation process and the mask removal process on the back surface of the substrate used to prevent the unevenness formed on the back surface of the substrate through the conventional wet method are not performed. The surface treatment time of the board | substrate 1 can be shortened.

That is, when manufacturing a crystalline silicon substrate for solar cells that does not have irregularities on the rear surface of the substrate 1, after forming a mask for preventing the formation of irregularities on the rear surface of the substrate 1 before the first surface treatment, and then subjected to etching treatment 1) Remove the mask formed on the back side. As a result, irregularities are formed only on the surface of the substrate.

Therefore, since the mask forming process and the mask removing process applied to the wet etching during the dry etching are unnecessary, the manufacturing cost can be reduced and the manufacturing time can be shortened, and a flat back surface can be secured.

Example

end. First surface treatment

Acidic aqueous solution: mixed at a ratio of 2: 1 with a substantial mass ratio of HNO ₃ and HF

Etching time: 1 ~ 10 minutes by inline method

Etching Temperature: About 6 ℃ ~ 10 ℃

I. Second surface treatment (dry etching; RIE)

CHF ₃ is about 12.0sccm, Cl ₂ is about 72sccm, O ₂ is about 9sccm and SF ₆ is about 65mcm and reaction pressure is about 50mTorr, and RF power for plasma is about 500W and it is about 5 seconds to 10 minutes. .

All. Comparison of Examples and Comparative Examples

As can be seen from the following Table 1, the reflectance of the substrate 1 surface-treated by the surface treatment method of the substrate according to the present invention can be seen that significantly reduced compared to the reflectance of the substrate surface-treated by the conventional method. .

division Reflectivity (%, 350 nm to 1050 nm) When only substrate damage treatment is performed 28.96 When substrate damage treatment and RIE are performed 10.51 When the first surface treatment and the second surface treatment are performed 7.79

Here, after the first surface treatment step and the second surface treatment step, which are the surface treatment methods of the substrate according to the present invention, the antireflection film 4 was formed by PECVD, the reflectance was 1.40.

Since the above has been described only with respect to some of the preferred embodiments that can be implemented by the present invention, the scope of the present invention, as is well known, should not be construed as limited to the above embodiments, the present invention described above It will be said that both the technical idea and the technical idea which together with the base are included in the scope of the present invention.

1 substrate 10 first unevenness
20: second unevenness

Claims

A first surface treatment step of etching the polycrystalline silicon substrate sliced from the polycrystalline silicon ingot with an acidic aqueous solution to form a plurality of first irregularities on the outer surface of the substrate;
And a second surface treatment step of forming a second unevenness having a smaller size than the first unevenness by dry etching a surface on which an antireflection film is to be formed among the outer surfaces of the substrate on which the first unevennesses are formed through the first surface treatment step. Surface treatment method of polycrystalline silicon substrate for solar cell.

The method according to claim 1,
The surface treatment method of the polycrystalline silicon substrate for solar cells, characterized in that the acidic aqueous solution in the first surface treatment step comprises HNO ₃ and HF.

The method according to claim 2,
The acidic aqueous solution is a surface treatment method of a polycrystalline silicon substrate for a solar cell, characterized in that the ratio of the actual mass ratio of HNO ₃ and HF in the aqueous solution is 1: 1 to 5.5: 1 mixed.

The method according to claim 1,
The first surface treatment step is performed while the substrate is transported by a roller, the surface treatment method of a polycrystalline silicon substrate for a solar cell, characterized in that the etching is performed for 1 to 10 minutes at a temperature of 6 ℃ ~ 10 ℃.

The method according to claim 1,
The first surface treatment step is performed by a dipping method in which etching is performed by immersing in a storage tank containing an acidic aqueous solution.
Surface treatment method of a polycrystalline silicon substrate for a solar cell, characterized in that the etching is performed for 20 minutes at a temperature of 6 ℃ ~ 10 ℃.

The method according to claim 1,
Before the first surface treatment step
And a substrate damage treatment step of removing the damage of the crystalline silicon substrate sliced from the crystalline silicon ingot with an acidic aqueous solution or an alkaline aqueous solution.

The method according to claim 1,
After the first surface treatment step, a first cleaning step of removing impurities generated in the first surface treatment step, a sub-etch process of partially etching the porous silicon dioxide remaining on the outer surface of the substrate using an alkali compound; A second cleaning step of removing impurities remaining on an outer surface of the substrate after the sub-etching step; And a drying step of drying the substrate after the second cleaning step.

The method according to claim 1,
A surface opposite to the surface on which the anti-reflection film is to be formed on the outer surface of the substrate on which the first irregularities are formed in the first surface treatment step after the first surface treatment step and before the second surface treatment step or after the second surface treatment step. And a back surface unevenness removing step of dry etching the back surface to remove the first unevenness formed on the back surface.

The method according to claim 1,
The second unevenness has a substantially triangular cross section, and the side of the first unevenness is formed to be shorter than the opposite side thereof. The surface treatment method of a polycrystalline silicon substrate for a solar cell.

The method according to any one of claims 1 to 9,
And said first unevenness is substantially hemispherical in cross section.

The method according to any one of claims 1 to 9,
After the first surface treatment step, the crystalline silicon substrate is formed of the surface of the surface etched in the first surface treatment step when the area of the surface on which the antireflection film is to be formed is completely planar. A surface treatment method of a polycrystalline silicon substrate for a solar cell, characterized in that the ratio of the actual surface area to the ideal area is 1.2 to 3.2.

10. A method of manufacturing a solar cell comprising the method of treating a surface of a crystalline silicon substrate for solar cells according to claim 1.

The method of claim 12,
After the first surface treatment step, the crystalline silicon substrate is formed of the surface of the surface etched in the first surface treatment step when the area of the surface on which the antireflection film is to be formed is completely planar. A method of manufacturing a solar cell, wherein the area ratio of the actual surface area to the ideal area is 1.2 to 3.2.

A first surface treatment step of forming a plurality of first irregularities on an outer surface of the substrate by etching the crystalline silicon substrate sliced from the crystalline silicon ingot with an acidic aqueous solution;
And a second surface treatment step of forming a second unevenness having a smaller size than the first unevenness by dry etching a surface on which an antireflection film is to be formed among the outer surfaces of the substrate on which the first unevennesses are formed through the first surface treatment step. ,
Before the first surface treatment step
And a substrate damage treatment step of removing the damage of the crystalline silicon substrate sliced from the crystalline silicon ingot with an acidic aqueous solution or an alkaline aqueous solution.

A first surface treatment step of forming a plurality of first irregularities on an outer surface of the substrate by etching the crystalline silicon substrate sliced from the crystalline silicon ingot with an acidic aqueous solution;
And a second surface treatment step of forming a second unevenness having a smaller size than the first unevenness by dry etching a surface on which an antireflection film is to be formed among the outer surfaces of the substrate on which the first unevennesses are formed through the first surface treatment step. ,
After the first surface treatment step, a first cleaning step of removing impurities generated in the first surface treatment step, a sub-etch process of partially etching the porous silicon dioxide remaining on the outer surface of the substrate using an alkali compound; A second cleaning step of removing impurities remaining on an outer surface of the substrate after the sub-etching step; And a drying step of drying the substrate after the second cleaning step.

A first surface treatment step of forming a plurality of first irregularities on an outer surface of the substrate by etching the crystalline silicon substrate sliced from the crystalline silicon ingot with an acidic aqueous solution;
And a second surface treatment step of forming a second unevenness having a smaller size than the first unevenness by dry etching a surface on which an antireflection film is to be formed among the outer surfaces of the substrate on which the first unevennesses are formed through the first surface treatment step. ,
A surface opposite to the surface on which the anti-reflection film is to be formed on the outer surface of the substrate on which the first irregularities are formed in the first surface treatment step after the first surface treatment step and before the second surface treatment step or after the second surface treatment step. And a back surface unevenness removing step of dry etching the back surface to remove the first unevenness formed on the back surface.