TWI544060B - Texture etching solution composition and texture etching method of crystalline silicon wafers - Google Patents

Description

Texture etching liquid composition and crystallization wafer texture etching method

The present application claims the priority of the Korean Patent Application No. 10-2011-0056075, filed on Jun.

The present invention relates to a texture etching solution composition for a crystalline germanium wafer capable of improving light absorption efficiency by forming a surface of the crystalline germanium wafer having a uniform micropyramid structure, and a texture etching method.

In recent years, solar cells have become rapidly popular, and are well known as the next generation of energy and electronic devices that directly convert clean energy, that is, convert sunlight into electricity. Such a solar cell basically has a P-type germanium semiconductor containing germanium and boron added thereto, and comprises a PN junction semiconductor substrate, which in principle comprises a p-type germanium semiconductor having germanium and boron added thereto, and by phosphorus (P) diffusing into the surface of the P-type germanium semiconductor to form an N-type germanium semiconductor layer.

When light, such as sunlight, illuminates a substrate having an electric field provided by a PN junction, electrons (-) and holes (+) in the semiconductor are excited, and such excited electrons (-) and holes (+) It can move freely and randomly within the semiconductor. In this case, formed by the PN junction Electrons (-) in the electric field can be moved into the N-type semiconductor, and the hole (+) is moved to the P-type semiconductor. If an electrode is provided on the surface of the P-type semiconductor and the N-type semiconductor to flow electrons toward an external circuit, a current is generated. Based on this principle, sunlight is converted into electrical energy. Therefore, in order to improve the solar conversion efficiency, the electric output per unit area of the PN junction semiconductor substrate should be increased as much as possible, and for this purpose, the reflectance must be reduced while maximizing the light absorption. In view of the foregoing, the germanium wafer for a solar cell constituting the PN junction semiconductor substrate should have a micropyramidal structure formed on the surface thereof, and an antireflection film can be provided. The surface of the germanium wafer that has been textured into a micropyramid structure reduces the reflectivity of incident light having a wide range of wavelengths, which in turn increases the amount of light absorbed. Therefore, the efficiency of the solar cell, that is, the efficiency of the solar cell can be improved.

A method for texturing a ruthenium wafer surface into a micro-pyramid structure has been disclosed. For example, U.S. Patent No. 4,137,123 describes a ruthenium texture etch solution in which 0.5 to 10% by weight of ruthenium is dissolved in an anisotropic etch (often In the "dry etching" solution, the isotropic etching solution contains 0 to 75% by volume of ethylene glycol, 0.05 to 50% by weight of potassium hydroxide, and the balance being water. However, such an etching solution causes a failure in pyramid formation, thus increasing light reflectance and causing a decrease in light absorption efficiency.

In addition, European Patent No. 0477424 proposes a texture etching method for feeding oxygen to a texture etching solution, that is, performing aeration process for several minutes, the texture etching solution comprising dissolving in ethylene glycol, potassium hydroxide and the remainder A mixture of water in a mixture. However, the above etching method causes failure of pyramid formation, which in turn increases light reflectivity while reducing light absorption efficiency, and furthermore has the disadvantage of further requiring an alternative venting device.

In addition, Korean Patent Registration No. 0180621 discloses a texture etching solution containing 0.5 to 5% potassium hydroxide solution, 3 to 20% by volume of isopropyl alcohol, and 75 to 96.5 vol%. A mixture of ionic water; U.S. Patent No. 6,451,218 discloses a textured etching solution comprising an alkaline earth metal compound, isopropanol, aqueous alkaline glycol, and water. However, since each of the above etching solutions includes isopropanol having a relatively low boiling point, and this material must be additionally introduced during texturing, it may cause economic disadvantages in terms of productivity and cost. In addition, the additionally introduced isopropanol causes a temperature gradient of the etching solution, thereby increasing the texture quality deviation in the area on the surface of the germanium wafer and ultimately reducing the uniformity.

Accordingly, it is an object of the present invention to provide a textured etching solution composition for a crystalline germanium wafer that provides improved texture uniformity within the region when a micropyramid structure is provided on the surface of the crystalline germanium wafer.

Another object of the present invention is to provide a texture etching solution composition for a crystalline germanium wafer without the application of an aeration process and the introduction of additional etching solution components during texturing.

Further, it is still another object of the present invention to provide a texture etching method using the foregoing texture etching solution composition for crystallizing a germanium wafer.

In order to accomplish the above object, the present invention provides the following.

(1) A texture etching solution composition for crystallizing a germanium wafer, comprising: 0.1 to 20% by weight of a basic compound; 10 to ^-9 to 10% by weight of a polysaccharide; and 10 to ⁹ to 10% by weight of cerium oxide a compound; and water as the remainder.

(2) The composition according to the above item (1), wherein the basic compound is selected from the group consisting of potassium hydroxide, sodium hydroxide, ammonium hydroxide, tetramethylolmonium, and tetrahydroxyethylammonium. At least one of them.

(3) The composition according to the above item (1), which is selected from the group consisting of a polydextrose compound, a polyfructose compound, a polymannose compound, and a polygalactose. At least one of the group consisting of a compound and a metal salt thereof.

(4) The composition according to the above item (3), wherein the polysaccharide is at least one polydextrose compound selected from the group consisting of cellulose, dimethylamino cellulose, and diethylaminoethyl cellulose. , ethyl hydroxyethyl cellulose, methyl hydroxyethyl cellulose, 4-aminobenzyl cellulose, triethylaminoethyl cellulose, cyanoethyl cellulose, ethyl cellulose, A Cellulose, carboxymethylcellulose, carboxyethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, alginic acid, amylose, amylopectin, pectin, starch, dextrin, alpha-ring Dextrin, β-cyclodextrin, γ-cyclodextrin, hydroxypropyl-β-cyclodextrin, methyl-β-cyclodextrin, dextrin, sodium dextrin, saponin, glycogen, A group consisting of zymosan, lentinan, Schizophyllum polysaccharide, and metal salts thereof.

(5) The composition according to the above item (3), which has an average molecular weight of 5,000 to 1,000,000.

(6) The composition according to the above item (1), wherein the cerium oxide compound is selected from the group consisting of ultrafine cerium oxide powder; a cerium sol solution stabilized with Na ₂ O; a cerium sol solution stabilized with K ₂ O; a ruthenium sol solution stabilized with an acidic solution; a ruthenium sol solution stabilized with NH ₃ ; a ruthenium sol solution stabilized with at least one organic solvent selected from the group consisting of ethanol, propanol, ethylene glycol, methyl ethyl ketone, and methyl isobutyl ketone At least one of the group consisting of ketones; liquid sodium citrate; liquid potassium citrate; and liquid lithium niobate.

(7) The composition according to the above item (1), further comprising at least one fluorosurfactant selected from the group consisting of perfluoroalkyl carboxylates and perfluoroalkyl sulfonates , perfluoroalkyl sulfate, perfluoroalkyl phosphate, perfluoroalkylamine salt, perfluoroalkyl quaternary ammonium salt, perfluoroalkylcarboxybetaine, perfluoroalkyl sulfobetaine, fluoroalkyl A group consisting of polyoxyethylene and perfluoroalkylpolyoxyethylene, each having an alkyl group of 1 to 30 carbon atoms.

(8) A texture etching method for a crystalline germanium wafer, comprising: immersing the crystalline germanium wafer in a texture etching according to any one of the above items (1) to (7) The composition is sprayed, the composition is sprayed, or the crystalline germanium wafer is immersed in the composition while the composition is sprayed onto the wafer.

(9) The method according to the above (8), wherein the immersing, spraying or immersing and spraying is performed at 50 to 100 ° C for 30 seconds to 60 minutes. According to the texture etching solution composition and the texture etching method for crystallizing germanium wafers according to the present invention, the amount of sunlight absorption can be maximized by improving the texture uniformity in the region on the surface of the crystalline germanium wafer, thereby reducing the light reflectance. With the enhancement of light absorption.

In addition, the present invention does not require the introduction of additional etching solution components or the application of aeration equipment during texturing, thereby enhancing quality and productivity while achieving economic advantages with respect to cost, as compared to conventional texture etching solution compositions.

The above and other objects, features and other advantages of the present invention will become apparent from the < The single crystal germanium wafer is texture etched by using the texture etching solution composition for crystallization of the germanium wafer prepared in Example 10 of the present invention; and FIG. 2 is a scanning electron microscope for explaining the surface of the single crystal germanium wafer ( SEM) photograph, the single crystal germanium wafer is textured etched by using the texture etching solution composition for crystallization of the germanium wafer prepared in Example 10 of the present invention.

The present invention provides a texture etching solution composition for a crystalline germanium wafer, and further, a crystalline germanium wafer texture etching method using the textured etching solution composition.

Hereinafter, the following description will be given to explain the present invention more specifically.

The texture etching solution composition for a crystalline germanium wafer according to the present invention may comprise an optimum content: a basic compound; a polysaccharide; a cerium oxide compound; and water as a remainder.

More specifically, the foregoing composition includes 0.1 to 20% by weight of a basic compound; 10 ^-9 to 10% by weight of a polysaccharide; 10 ^-9 to 10% by weight of a cerium oxide compound; and water as a remainder.

The basic compound is a component that etches the surface of the crystallization wafer, and the kind of the component is not particularly limited. For example, potassium hydroxide, sodium hydroxide, ammonium hydroxide, tetramethylolmonium chloride, tetrahydroxyethylammonium or the like is used, and among them, potassium hydroxide or sodium hydroxide is preferably used. These compounds are used singly or in combination of two or more thereof.

The basic compound may be included in an amount of 0.1 to 20% by weight, preferably 1 to 5% by weight, based on 100% by weight of the total etching solution compound for crystallizing the ruthenium wafer. When the content of the basic compound is within the above range, the surface of the tantalum wafer can be etched.

The texture etching solution composition for a crystalline germanium wafer according to the present invention may further comprise a polysaccharide having an optimum content.

A polysaccharide is a saccharide containing two or more monosaccharides to form a macromolecule via glycosidation, preventing over-etching, and effectively controlling etch acceleration by using a basic compound to prepare a uniform micro-pyramid, The hydrogen bubbles generated by etching off the surface of the wafer are quickly reduced, thereby preventing the occurrence of bubble sticking.

Examples of the polysaccharide may include; a polydextrose compound, a polyfructose compound, a polymannose compound, a polygalactose compound, and a metal salt thereof. Among these, polydextrose compounds and metal salts thereof (for example, basic metal salts) are preferably used. The foregoing substances may be used singly or in combination of two or more thereof.

The polydextrose compound may include, for example, cellulose, dimethylaminoethylcellulose, diethylaminoethylcellulose, ethylhydroxyethylcellulose, methylhydroxyethylcellulose, 4-amine Base benzyl cellulose, triethylaminoethyl cellulose, cyanoethyl cellulose, ethyl cellulose, methyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, hydroxyethyl cellulose , hydroxypropyl cellulose, alginic acid, amylose, amylopectin, pectin, starch, dextrin, α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, hydroxypropyl-β- Cyclodextrin, methyl-β-cyclodextrin, dextrin, sodium dextrosodium succinate, saponin, glycogen, zymosan, lentinan, Schizophyllum polysaccharide, and metal salts thereof.

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

The polysaccharide may be included in the content of 10 ^-9 to 10% by weight, and preferably 10 ^-6 to 1% by weight, relative to 100% by weight of the texture etching solution composition for crystallizing the ruthenium wafer. If the content of the polysaccharide is within the foregoing range, excessive etching can be prevented, and etching acceleration can be effectively controlled. When the content exceeds 10% by weight, when a basic compound is used, the etching rate may suddenly decrease, resulting in difficulty in forming a desired micropyramid.

The texture etching solution composition for crystallizing the germanium wafer may further include a cerium oxide compound.

The cerium oxide compound can be physically adsorbed onto the surface of the crystalline germanium wafer and act as a mask, thus enabling the surface of the germanium wafer to be in the form of a micro-pyramid.

The cerium oxide compound may include a powdery, colloidal solution or a liquid metal silicate compound. More particularly, an ultrafine cerium oxide powder; a cerium sol solution stabilized with Na ₂ O; a cerium sol solution stabilized with K ₂ O; a cerium sol solution stabilized with an acidic solution; a cerium sol solution stabilized with NH ₃ ; a cerium sol solution stabilized with at least one organic solvent selected from the group consisting of ethanol, propanol, ethylene glycol, methyl ethyl ketone, and methyl isobutyl ketone; liquid sodium citrate; liquid potassium citrate; Lithium niobate and so on. The foregoing materials may be used singly or in combination of two or more thereof.

The cerium oxide compound may be included in an amount of 10 ^-9 to 10% by weight, and preferably 10 ^-6 to 1% by weight, based on the total 100% by weight of the texture etching solution compound for crystallizing the cerium wafer. If the amount is within the foregoing range, the micropyramid can be easily formed on the surface of the crystallization wafer.

The texture etching solution composition for crystallizing a germanium wafer according to the present invention may further include a fluorine surfactant.

Fluorine surfactant and polyoxygen compound-based interface The active agent reduces the surface tension of the etching solution composition, thereby promoting the improvement of the surface wettability of the crystallization wafer and ultimately preventing over-etching by the alkaline compound.

The kind of the fluorosurfactant is not particularly limited, but may include, for example, an anionic surfactant such as a perfluoroalkyl carboxylate, a perfluoroalkylsulfonate, a perfluoroalkylsulfate, a perfluoroalkyl group. Phosphate, etc.; cationic surfactants such as perfluoroalkylamine salts, perfluoroalkyl quaternary ammonium salts, etc.; amphoteric surfactants such as perfluoroalkylcarboxybetaine, perfluoroalkylsulfonyl Betaine, etc.; nonionic surfactants such as fluoroalkyl polyoxyethylene, perfluoroalkyl polyoxyethylene, and the like. This compound may have an alkyl group of 1 to 30 carbon atoms. These materials may be used singly or in combination of two or more thereof.

The fluorosurfactant may be included in an amount of from 10 ^-9 to 10% by weight, and preferably from 10 ^-6 to 1% by weight, based on the total 100% by weight of the texture etching solution composition for crystallizing the ruthenium wafer. If the amount is within the above range, the wettability of the surface of the tantalum wafer can be effectively improved.

The texture etching solution composition for the crystalline germanium wafer may further include water as the remainder of the total 100% by weight of the composition.

The type of water is not particularly limited, however, it is preferably deionized water and, more preferably, deionized water for a semiconductor process having a specific resistance of 18 M?/cm or higher.

In addition to the polysaccharide, the use of the aforementioned ingredients is used according to the invention The texture etching solution composition on the crystalline germanium wafer may include a cerium oxide compound, thereby maximizing the amount of sunlight absorption while reducing the light reflectance by forming a surface of the crystalline germanium wafer having a uniform micropyramid structure With the enhancement of light absorption. In addition, the inventive texture etching solution composition requires neither the introduction of additional etching solution components nor the application of aeration during texturing, thus achieving excellent productivity and economic advantages with respect to cost.

The texture etching solution composition for a crystalline germanium wafer according to the present invention can be suitably used in a usual etching process such as dipping, spraying, embedding type etching, and the like.

The present invention provides a texture etching method for a crystalline germanium wafer using the above-described texture etching solution composition for crystallizing germanium wafers.

The texture etching method of the crystalline germanium wafer may include immersing the crystalline germanium wafer in an etching solution composition for crystallizing the germanium wafer, spraying the composition, or simultaneously spraying the crystalline germanium wafer while being immersed therein.

The number of times of immersion and/or spraying may not be particularly limited, and the order of operation may not be limited in the example in which the immersion and spraying are simultaneously performed.

Immersion, spraying or immersion and spraying can be carried out at 50 to 100 ° C for 30 seconds to 60 minutes.

As described above, the crystalline germanium wafer texture etching method according to the present invention does not require the introduction of additional ventilation equipment to supply oxygen, and therefore is economical in terms of starting production and processing costs, and even by simple The process can also form a consistent micropyramid structure.

In the following, preferred embodiments will be described, and the present invention will be more specifically understood by reference to the examples and comparative examples. However, it will be apparent to those skilled in the art that the present invention may be Such modifications and variations are fully encompassed by the invention as defined by the scope of the appended claims.

example

Example 1

By mixing 4% by weight of potassium hydroxide (KOH), 0.005% by weight of diethylaminoethylcellulose (DMAEC), 0.2% by weight of liquid sodium citrate (SSS) and as the remainder of the deionized water A texture etching solution composition for crystallizing the germanium wafer is prepared.

Examples 2 to 14 and Comparative Examples 1 to 4

The same procedure as described in Example 1 was carried out except that the basic components listed in Table 1 below and their contents were used. Here, the content means % by weight.

[Table 1]

Comparative example 5

A texture etching solution composition for a crystalline germanium wafer was prepared by mixing 1.5% by weight of potassium hydroxide (KOH), 5% by weight of isopropyl alcohol (IPA), and as the remainder of the deionized water.

Comparative example 6

The same procedure as described in Comparative Example 5 was performed except that ethylene glycol (EG) was substituted for isopropanol (IPA).

Comparative example 7

The same procedure as described in Comparative Example 5 was performed except that methyl diglycol (MDG) was used instead of isopropyl alcohol (IPA).

Comparative example 8

The same procedure as described in Comparative Example 5 was performed except that isopropanol (IPA) was replaced with monoethylamine (MEA).

Exemplary example

The texture etching effect of each of the prepared texture etching solution compositions for the crystalline germanium wafer according to the above examples and comparative examples was evaluated by the following procedure, and the results are shown in Table 2: The wafer substrate was immersed in a prepared texture etching solution composition for a single crystal germanium wafer at 80 ° C for 20 minutes.

(1) Texture uniformity

The texture deviation, that is, uniformity, formed on the surface of the single crystal germanium wafer substrate obtained after the texture etching was visually observed through a digital camera, a 3D optical microscope, and a scanning electron microscope (SEM), and evaluated according to the following criteria. .

<Evaluation criteria>

◎ - Pyramid is formed on the entire wafer substrate.

○-The pyramid is not formed on a part of the wafer substrate (less than 5% of the portion without the pyramid).

The delta-pyramid is not formed on a portion of the wafer substrate (the portion having no pyramid ranges from 5 to 50%).

The x-pyramid is not formed on substantially the majority of the wafer substrate (the portion without the pyramid is 90% or more).

(2) Average pyramid size (μm)

The size of each micropyramid formed on the surface of the single crystal germanium wafer substrate obtained after the texture etching was measured using a scanning electron microscope (SEM). Here, after measuring the size of each micro-pyramid formed on a unit area, the average of the measured sizes is calculated.

(3) Average reflectance (%)

In an example in which a light having a wavelength range of 400 to 800 nm is irradiated on the surface of a single crystal germanium wafer substrate obtained after texture etching, an average reflectance is measured using a UV spectrometer.

[Table 2]

As shown in Table 2, in an example of performing texture etching using any of the texture etching solution compositions prepared in Examples 1 to 14 of the present invention, the texture etching solution composition includes a basic compound; a polysaccharide; cerium oxide The compound; and the water having the desired content as the remainder, exhibits improved texture uniformity of the micropyramids formed on the surface of the textured etched wafer, thereby reducing light reflectivity and, consequently, improving light absorption efficiency.

Figure 1 is a 3D optical microscope image showing the use The texture etching solution composition prepared in Example 10 was used to texture the surface of the crystalline germanium wafer obtained after etching; and FIG. 2 is an SEM photograph showing the surface of the crystalline germanium wafer obtained after the texture etching as described above. From these images, it can be confirmed that the micro-pyramid has been formed on the entire wafer surface by enhancing the uniformity of the texture while reducing the variation in quality.

On the other hand, when the texture etching solution composition containing no polysaccharide prepared in Comparative Example 1 was used, the pyramid size was large due to the fast etching rate, and there was a small pyramid; and it was found that, in comparison, The product of the non-ruthenium dioxide compound of Sexual Example 2 exhibits a portion in which no pyramid is formed. Further, when the texture etching solution composition containing the excess polysaccharide prepared in Comparative Example 3 was used, the desired effect was not sufficiently obtained due to insufficient dissolution of the cerium oxide compound; and when Comparative Example 4 was used When a texture etching solution composition containing an excessive amount of polysaccharide is prepared, the etching rate is greatly reduced, thereby increasing the light reflectance. Further, regarding the texture etching solution composition prepared in Comparative Example 5, due to the low boiling point of the isopropyl alcohol (IPA) included in the etching solution composition, the temperature gradient caused by the continuous introduction of the composition during texturing has been Causes texture failure and increased cost. The texture etching solution composition in Comparative Example 6 exhibited a rather deteriorated characteristic with respect to texture uniformity and light reflectance as compared with the example. The texture etching solution compositions of Comparative Examples 7 and 8 showed self-change over time and the temperature was raised to the texture processing temperature.

While the invention has been described with respect to the preferred embodiments the embodiments of the present invention

Claims (8)

A texture etching solution composition for a crystalline germanium wafer comprising: 0.1 to 20% by weight of a basic compound; 10 to ⁹ to 10% by weight of a polysaccharide; 10 to ⁹ to 10% by weight of one or two a cerium oxide compound; and water as a remainder, wherein the cerium oxide compound is at least one selected from the group consisting of liquid sodium citrate, liquid potassium citrate, and liquid lithium niobate. The composition of claim 1, wherein the basic compound is selected from the group consisting of potassium hydroxide, sodium hydroxide, ammonium hydroxide, tetramethylolmonium, and tetrahydroxyethylammonium. At least one of them. The composition of claim 1, wherein the polysaccharide is selected from the group consisting of a polydextrose compound, a polyfructose compound, a polymannose compound, a polygalactose compound, and a metal salt thereof. At least one of them. The composition of claim 3, wherein the polysaccharide is at least one polydextrose compound selected from the group consisting of cellulose, dimethylaminoethyl cellulose, and diethylaminoethyl fiber. , ethyl hydroxyethyl cellulose, methyl hydroxyethyl cellulose, 4-aminobenzyl cellulose, triethylaminoethyl cellulose, cyanoethyl cellulose, ethyl cellulose, A Cellulose, carboxymethylcellulose, carboxyethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, alginic acid, amylose, amylopectin, pectin, starch, dextrin, alpha-ring Dextrin, β-cyclodextrin, γ-cyclodextrin, hydroxypropyl-β-cyclodextrin, methyl-β-cyclodextrin, dextrin, sodium dextrin, saponin, glycogen, A group consisting of zymosan, lentinan, Schizophyllum polysaccharide, and metal salts thereof. The composition of claim 3, wherein the polysaccharide has a median molecular weight of 5,000 to 1,000,000. The composition of claim 1, further comprising at least one fluorosurfactant selected from the group consisting of perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and perfluoroalkyl sulfates. Salt, perfluoroalkyl phosphate, perfluoroalkylamine salt, perfluoroalkyl quaternary ammonium salt, perfluoroalkylcarboxybetaine, perfluoroalkyl sulfobetaine, fluoroalkyl polyoxyethylene, and perfluoro A group consisting of alkyl polyoxyethylenes each having a monoalkyl group of 1 to 30 carbon atoms. A texture etching method for a crystalline germanium wafer, comprising: immersing the crystalline germanium wafer in a texture etching solution composition according to any one of claims 1 to 6, spraying the composition Or immersing the crystallization wafer in the composition while spraying the composition onto the wafer. The method of claim 7, wherein the immersing, spraying, or immersing and spraying are performed at 50 to 100 ° C for 30 seconds to 60 minutes.