KR20150106221A

KR20150106221A - Texture etching solution composition and texture etching method of crystalline silicon wafers

Info

Publication number: KR20150106221A
Application number: KR1020140028460A
Authority: KR
Inventors: 임대성; 홍형표; 박면규
Original assignee: 동우 화인켐 주식회사
Priority date: 2014-03-11
Filing date: 2014-03-11
Publication date: 2015-09-21

Abstract

TECHNICAL FIELD The present invention relates to a texture etchant composition for a crystalline silicon wafer and a method of etching the same, and more particularly, to a process for etching a crystalline silicon wafer, which comprises an alkali compound, a lignosulfonate salt and a polyethylene glycol compound having a specific structure, A texture etchant composition of a crystalline silicon wafer which improves light efficiency by minimizing the quality deviation of texture by position by controlling the difference in the etching rate with respect to the silicon crystal direction in the formation of the fine pyramidal structure by preventing the overetching by the alkali compound And a texture etching method.

Description

TECHNICAL FIELD [0001] The present invention relates to a texture etching liquid composition for a crystalline silicon wafer and a texture etching method for a crystalline silicon wafer,

The present invention relates to a texture etchant composition and a texture etching method for a crystalline silicon wafer that minimizes texture quality deviations of the surface of a crystalline silicon wafer and does not cause a temperature gradient during etching.

Solar cells, which are rapidly spreading in recent years, are electronic devices that convert solar energy, which is a clean energy source, directly into electricity. The solar cell is composed of a p-type silicon semiconductor in which boron is added to silicon, and a pn junction semiconductor substrate in which phosphorus is diffused on its surface to form an n-type silicon semiconductor layer.

When a light such as sunlight is irradiated to a substrate formed with an electric field by a PN junction, electrons (-) and holes (+) in the semiconductor are excited to move freely in the semiconductor and the electric field generated by the PN junction When it comes in, the electrons (-) lead to the N-type semiconductor and the positive (+) lead to the P-type semiconductor. When an electrode is formed on the surface of a p-type semiconductor and an n-type semiconductor and an electron flows to an external circuit, a current is generated. This principle converts solar energy into electrical energy. Therefore, in order to increase the conversion efficiency of solar energy, the electrical output per unit area of the PN junction semiconductor substrate must be maximized. For this, the reflectance should be lowered and the light absorption amount should be maximized. In consideration of this point, the surface of the silicon wafer for a solar cell constituting the PN junction semiconductor substrate is formed into a fine pyramid structure and the antireflection film is processed. The surface of a silicon wafer textured with a fine pyramid structure lowers the reflectance of incident light having a wide wavelength band, thereby increasing the intensity of the absorbed light, thereby enhancing the performance of the solar cell, that is, efficiency.

US Pat. No. 4,137,123 discloses a method of texturing a surface of a silicon wafer with a fine pyramid structure by adding 0.5 to 10 wt. % Of silicon is dissolved in a solvent. However, this etchant may cause pyramid formation failure to increase the light reflectance and lower the efficiency.

Korean Patent No. 0180621 discloses a texture etching solution mixed at a ratio of 0.5-5% of a potassium hydroxide solution, 3-20% by volume of isopropyl alcohol and 75-96.5% by volume of deionized water, and US Patent No. 6,451,218 Discloses a texturing etch solution comprising an alkaline compound, isopropyl alcohol, water soluble alkaline ethylene glycol and water. However, since these etching solutions contain isopropyl alcohol having a low boiling point, it is not economical from the viewpoint of productivity and cost, because it is required to add the additional isopropyl alcohol in the texture process, and the temperature gradient of the etchant is generated due to the added isopropyl alcohol, And the uniformity of the texture may be deteriorated.

U.S. Patent No. 4,137,123 Korean Patent No. 10-0180621 U.S. Patent No. 6,451,218

In forming a fine pyramid structure on the surface of a crystalline silicon wafer, the present invention controls the difference in the etching rate with respect to the direction of the silicon crystal to prevent over etching by the alkali compound, thereby minimizing the quality deviation of the texture per position, Which is an object of the present invention, to provide a texture etching liquid composition for a crystalline silicon wafer.

Another object of the present invention is to provide a texture etching method using the texture etching liquid composition of the crystalline silicon wafer.

1. A textured etching solution composition for a crystalline silicon wafer comprising an alkali compound lignosulfonate salt and a compound represented by the following formula:

[Chemical Formula 1]

(Wherein R is an alkyl group having 1 to 6 carbon atoms or a phenyl group, X is independently hydrogen or a methyl group, y is an integer of 1 to 3, and M is an alkali metal.)

2. The texture etchant composition of claim 1, wherein M is sodium or potassium.

3. The composition of claim 1, wherein the lignosulfonic acid salt is at least one of sodium lignosulfonate and calcium lignosulfonate.

4. The composition for etching a crystalline silicon wafer according to 1 above, wherein the alkali compound is at least one selected from the group consisting of potassium hydroxide, sodium hydroxide, ammonium hydroxide, tetrahydroxymethylammonium, and tetrahydroxyethylammonium.

5. The texture etch composition of claim 1, wherein the alkaline compound comprises 0.5 to 5 wt%, the compound of formula (1) is 0.001 to 5 wt%, and the balance water.

6. A method of etching a crystalline silicon wafer with an etchant composition according to any one of claims 1 to 4.

7. The etching method according to 5 above, wherein said etching solution composition is sprayed at a temperature of 50 to 100 DEG C for 30 seconds to 60 minutes.

8. The etching method according to claim 5, wherein the wafer is immersed in the etching liquid composition at a temperature of 50 to 100 DEG C for 30 seconds to 60 minutes.

According to the texture etchant composition and texture etching method of the crystalline silicon wafer of the present invention, the difference in the etching rate with respect to the silicon crystal direction can be controlled even with a low concentration of the etching solution composition to prevent over etching by the alkali compound, And the formed pyramid has a fine pyramid structure with a small size, the uniformity of the texture is improved to maximize the absorption of sunlight.

1 is an SEM photograph of the surface of a single crystal silicon wafer substrate etched using the etching solution composition for a texture of the crystalline silicon wafer of Example 1. Fig.
2 is an optical microscope (magnification 1,000 times) photograph of the surface of a single crystal silicon wafer substrate etched using the etching solution composition for a texture of the crystalline silicon wafer of Example 3. Fig.
3 is an SEM photograph of the surface of a single crystal silicon wafer substrate etched using the etching solution composition for a texture of the crystalline silicon wafer of Example 5;
4 is an SEM photograph of the surface of a single crystal silicon wafer substrate etched using the etching solution composition for a texture of the crystalline silicon wafer of Comparative Example 1. Fig.
5 is an optical microscope (magnification 1,000 times) photograph of the surface of a single crystal silicon wafer substrate etched using the etching solution composition for a texture of the crystalline silicon wafer of Comparative Example 3. Fig.

The present invention includes an alkaline compound, a lignosulfonate salt, and a polyethylene glycol compound having a specific structure, so that when forming a fine pyramid structure on the surface of a crystalline silicon wafer, the difference in etching rate with respect to the direction of silicon crystal is controlled, And to a method of etching a textured etchant of a crystalline silicon wafer and a method of etching the same that minimizes quality deviations of a texture by position to increase light efficiency.

Hereinafter, the present invention will be described in detail.

The texture etchant composition of the crystalline silicon wafer of the present invention comprises an alkali compound, a lignosulfonate salt and a polyethylene glycol compound having a specific structure.

The polyethylene glycol compound having a specific structure according to the present invention is represented by the following formula (1).

[Chemical Formula 1]

Wherein R is an alkyl group having 1 to 6 carbon atoms or a phenyl group, X is independently hydrogen or a methyl group, y is an integer of 1 to 3, and M is an alkali metal. Preferably, M is sodium or potassium.

The compound of Chemical Formula 1 according to the present invention exhibits a better controllability of the etching rate on the (100) plane and the (111) plane, which are the directions of the silicon crystal. Particularly, when the single crystal Si is etched by the alkali compound, The etching rate in the (100) direction by the alkaline compound is prevented to prevent the over etching by the alkali compound, thereby minimizing the quality deviation of the texture and improving the wettability of the surface of the crystalline silicon wafer, It is possible to prevent the occurrence of the bubble stick phenomenon by rapidly dropping from the silicon surface, thereby improving the quality of the texture.

One embodiment of the process for preparing the compound of formula (1) according to the present invention includes the following reaction formula (1).

[Reaction Scheme 1]

That is, it can be obtained by reacting an ether compound of polyethylene glycol and R with an alkali metal or a salt or hydroxide thereof. In one embodiment of the present invention, the use of an alkali metal salt (for example, a hydride compound of an alkali metal) or an alkali metal may be more preferable because less unreacted product is generated than using a hydroxide of an alkali metal .

The compound of formula (I) according to the present invention may be contained in an amount of 0.001 to 5% by weight, preferably 0.01 to 2% by weight, based on the total weight of the texture etching liquid composition of the crystalline silicon wafer. When the content falls within the above range, etching and etching acceleration can be effectively prevented. When the content is less than 0.001% by weight, it is difficult to control the etching rate by the alkaline compound, and it is difficult to obtain a uniform texture shape. When the content exceeds 5% by weight, the etching rate by the alkali compound is rapidly lowered to form a desired fine pyramid It may be difficult to do.

The lignosulfonic acid salt according to the present invention can control the etching rate and can form a small and uniform texture shape on the silicon surface with a small amount of use. Examples of the lignosulfonic acid salt that can be used include sodium lignosulfonate and calcium lignosulfonate, among which sodium lignosulfonate is preferable. These may be used alone or in combination of two or more.

The lignosulfonic acid salt may be contained in an amount of 0.0001 to 0.1% by weight, preferably 0.001 to 0.02% by weight, based on the total weight of the etching liquid composition of the crystalline silicon wafer. When the content falls within the above range, a small and uniform texture shape can be formed on the surface of the silicon wafer. If the content of the lignosulfonic acid salt is less than 0.0001 wt%, the etching rate of the alkaline compound to the silicon wafer can not be controlled and a small and uniform texture shape may not be obtained. If the content is more than 0.1 wt% It may not be possible to obtain a uniform texture shape.

The alkaline compound according to the present invention can be used without limitation as long as it is an alkaline compound commonly used in the art as a component for etching the surface of a crystalline silicon wafer. Examples of the alkali compound that can be used include potassium hydroxide, sodium hydroxide, ammonium hydroxide, tetrahydroxymethylammonium, and tetrahydroxyethylammonium. Of these, potassium hydroxide and sodium hydroxide are preferable. These may be used alone or in combination of two or more.

The alkali compound may be contained in an amount of 0.5 to 5% by weight, and preferably 1 to 3% by weight based on the total weight of the texture etching liquid composition of the crystalline silicon wafer. When the content falls within the above range, the surface of the silicon wafer can be etched.

The texture etchant composition of the crystalline silicon wafer according to the present invention may appropriately employ the above-mentioned components according to specific needs, and then add water to adjust the overall composition, so that the remaining amount of the entire composition is occupied by water. Preferably, the components are adjusted to have the aforementioned content ranges.

The kind of water is not particularly limited, but it is preferably deionized distilled water. More preferably, it is deionized distilled water for semiconductor processing and has a specific resistance value of 18 M? · Cm or more.

Optionally, it may further include additional additives known in the art to the extent that the objects and effects of the present invention are not impaired. Examples of such components include a viscosity adjusting agent and a pH adjusting agent.

Examples of the viscosity adjusting agent include a polysaccharide. A polysaccharide is a saccharide compound in which two or more monosaccharides are linked by glycosidation to form a large molecule.

Examples of the polysaccharide include a glucan compound, a fructan compound, a mannan compound, a galactan compound or a metal salt thereof. Among them, a glucan compound and its metal salt (for example, , Alkali metal salts) are preferable. These may be used alone or in combination of two or more.

Examples of the glucan compound include cellulose, dimethylaminoethylcellulose, diethylaminoethylcellulose, ethylhydroxyethylcellulose, methylhydroxyethylcellulose, 4-aminobenzylcellulose, triethylaminoethylcellulose, cyanoethylcellulose, ethylcellulose, But are not limited to, cellulose, carboxymethylcellulose, carboxyethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, alginic acid, amylose, amylopectin, pectin, starch, dextrin,? -Cyclodextrin,? -Cyclodextrin, Cyclodextrin, methyl- beta -cyclodextrin, dextran, sodium dextran sulfate, saponin, glycogen, zymo acid, lentinan, sijofinan or metal salts thereof.

The polysaccharide may have an average molecular weight of 5,000 to 1,000,000, preferably 50,000 to 200,000.

The polysaccharide may be contained in an amount of 10-9 to 0.5 wt%, preferably 10-6 to 0.1 wt%, based on the total weight of the texture etching liquid composition of the crystalline silicon wafer. When the content falls within the above range, etching and etching acceleration can be effectively prevented. When the content is more than 0.5% by weight, the etching rate by the alkali compound is rapidly lowered and it is difficult to form the desired fine pyramid.

The texture etchant composition of the crystalline silicon wafer of the present invention can be applied to a general etching process, for example, a dip process, a spray process, and a sheet-process etching process.

The present invention provides a method of etching a crystalline silicon wafer using the texture etchant composition of the crystalline silicon wafer.

The method of texturing a crystalline silicon wafer includes the steps of depositing a crystalline silicon wafer on the texture etchant composition of the crystalline silicon wafer of the present invention or by spraying a textured etchant composition of the crystalline silicon wafer of the present invention onto a crystalline silicon wafer Step, or both of the above steps.

The number of times of deposition and spraying is not particularly limited, and the order of deposition and spraying is not limited.

The step of depositing, spraying or depositing and spraying can be carried out at a temperature of 50 to 100 캜 for 30 seconds to 60 minutes.

The texture etching method of the crystalline silicon wafer of the present invention as described above is not only economical in terms of initial production and processing cost but also requires no separate airrating equipment for supplying oxygen, Structure.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to be illustrative of the invention and are not intended to limit the scope of the claims. It will be apparent to those skilled in the art that such variations and modifications are within the scope of the appended claims.

Example And Comparative Example

Water (H ₂ O) was added to the components and the contents shown in Table 1 below to prepare an etching liquid composition for a texture of a crystalline silicon wafer.

The compound (A) The alkali compound (B) Lignosulfonate R X y M content
(weight%) Material name content
(weight%) Material name content
(weight%) Example 1 C ₄ H ₉ H 3 Na 0.03 KOH 1.5 Sodium lignosulfonate 0.001 Example 2 0.04 KOH 1.5 Sodium lignosulfonate 0.002 Example 3 0.05 KOH 2.0 Sodium lignosulfonate 0.003 Example 4 0.04 KOH 2.0 Sodium lignosulfonate 0.120 Example 5 C ₂ H ₅ H 3 Na 0.03 KOH 2.0 Sodium lignosulfonate 0.002 Example 6 0.04 KOH 1.5 Sodium lignosulfonate 0.003 Example 7 0.05 KOH 2.0 Sodium lignosulfonate 0.004 Example 8 0.08 KOH 2.0 Sodium lignosulfonate 0.002 Example 9 2.4 KOH 2.0 Sodium lignosulfonate 0.002 Example 10 5.2 KOH 2.0 Sodium lignosulfonate 0.002 Comparative Example 1 C ₂ H ₅ H 3 Na 0.04 KOH 1.5 - - Comparative Example 2 C ₄ H ₉ H 3 Na 0.05 KOH 2.0 Comparative Example 3 - - - - - KOH 2.0 Sodium lignosulfonate 0.002 Comparative Example 4 C ₄ H ₉ H 3 H 0.10 KOH 2.0 Sodium lignosulfonate 0.002

Experimental Example

Single crystal silicon wafers were respectively immersed in etching solution compositions for texturing of crystalline silicon wafers of Examples and Comparative Examples and etched. At this time, the texture condition was a temperature of 80 ° C and a time of 20 minutes.

1. Etching amount

The weight change of the wafer before and after the etching was measured, and the results are shown in Table 2.

2. Texture Reflectance evaluation

The reflectance of the surface of the etched monocrystalline silicon wafer when irradiated with light having a wavelength of 600 nm was measured using a UV spectrophotometer, and the results are shown in Table 2.

3. Texture Uniformity evaluation

The surface of the etched monocrystalline silicon wafer was evaluated using an optical microscope and SEM. The results are shown in Table 2.

◎: Formation of wafer front pyramid

?: Partial pyramid formation of wafer

(Less than 5% of pyramid structure unformed)

DELTA: Partial pyramid formation of wafer

(About 5 to 50% of pyramidal structure unformed)

Х: Wafer pyramid not formed

(Degree of formation of pyramid not less than 90%)

4. Pyramid size

The size of the pyramid formed on the surface of the etched monocrystalline silicon wafer was measured using SEM. The results are shown in Table 2 below.

10: The average size of the pyramid exceeds 10 탆

8: The average size of the pyramid is more than 8 탆 and not more than 10 탆

6: The average size of the pyramid is more than 6 탆 and not more than 8 탆

4: Average size of pyramid exceeding 4 탆 and below 6 탆

2: average size of pyramid is less than 4 탆

division Evaluation results Etching amount (g) reflectivity(%) Exterior Pyramid's
Average size range Example 1 0.52 11.8 ◎ 2 Example 2 0.48 11.6 ◎ 4 Example 3 0.55 12.0 ◎ 2 Example 4 0.38 13.8 △ 4 Example 5 0.60 12.2 ◎ 2 Example 6 0.65 11.9 ◎ 2 Example 7 0.50 12.1 ○ 6 Example 8 0.48 11.7 ◎ 2 Example 9 0.52 10.9 ○ 6 Example 10 0.38 13.2 △ 6 Comparative Example 1 0.76 10.8 ◎ 8 Comparative Example 2 0.68 11.2 ◎ 8 Comparative Example 3 1.01 14.8 X 2 Comparative Example 4 0.98 13.9 △ 2

Referring to Table 2 and FIGS. 1 to 5, the etchant compositions of the silicon wafers of the Examples show a very small and uniform pyramid formation on the entire surface of the single crystal silicon wafer compared to the comparative examples, . It was confirmed by optical microscope or SEM analysis that high-density pyramid was formed by magnifying the pyramid at high magnification.

However, in Example 4 in which the sodium lignosulfonate salt was used in a rather excessive amount, it was confirmed that the reflectance was somewhat high and the uniformity was slightly lowered on the wafer surface.

In addition, in Example 10, in which the compound of Formula 1 was used in a rather excessive amount, it was confirmed that the reflectance was somewhat high, the uniformity was slightly lowered on the wafer surface, and the pyramid size was somewhat larger.

However, in Comparative Examples 1 and 2, it was confirmed that a pyramid was well formed on the entire surface of a silicon wafer, but a pyramid formed thereon was formed larger than those of the examples, when the sodium lignosulfonate salt was not used.

In addition, it was confirmed that the texture structure of Comparative Example 3 was hardly formed. In Comparative Example 4, it was confirmed that a hydrogen-bonded compound was used instead of an alkali metal in the compound of Chemical Formula 1, and a pyramid having a high reflectivity and a non-uniformity was formed under the same conditions as those of Examples.

Claims

1. A textured etching solution composition for a crystalline silicon wafer comprising an alkali compound, a lignosulfonate salt and a compound represented by the following formula:
[Chemical Formula 1]

The composition of claim 1, wherein M is sodium or potassium.

The composition of claim 1, wherein the lignosulfonate salt is at least one of sodium lignosulfonate and calcium lignosulfonate.

The composition according to claim 1, wherein the alkali compound is at least one selected from the group consisting of potassium hydroxide, sodium hydroxide, ammonium hydroxide, tetrahydroxymethylammonium, and tetrahydroxyethylammonium.

2. The composition of claim 1, wherein the composition comprises 0.5 to 5% by weight of an alkali compound, 0.0001 to 0.1% by weight of a lignosulfonate salt, 0.001 to 5% by weight of a compound of the formula 1 and water in a residual amount.

A method of etching a crystalline silicon wafer using the etchant composition of any one of claims 1 to 5.

7. The etching method according to claim 6, comprising spraying the etchant composition at a temperature of 50 to 100 DEG C for 30 seconds to 60 minutes.

7. The etching method according to claim 6, wherein the wafer is immersed in the etching liquid composition at a temperature of 50 to 100 DEG C for 30 seconds to 60 minutes.