WO2011052941A2 - Etching composition for texturing crystalline silicon-based wafer - Google Patents

Etching composition for texturing crystalline silicon-based wafer Download PDF

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WO2011052941A2
WO2011052941A2 PCT/KR2010/007323 KR2010007323W WO2011052941A2 WO 2011052941 A2 WO2011052941 A2 WO 2011052941A2 KR 2010007323 W KR2010007323 W KR 2010007323W WO 2011052941 A2 WO2011052941 A2 WO 2011052941A2
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Prior art keywords
etching composition
texturing
ine
pyrrolidone
etching
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PCT/KR2010/007323
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French (fr)
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WO2011052941A3 (en
Inventor
Hyung-Pyo Hong
Jae-Youn Lee
Dae-Sung Lim
Seung-Yong Lee
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Dongwoo Fine-Chem Co., Ltd.
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Publication of WO2011052941A3 publication Critical patent/WO2011052941A3/en

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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K13/00—Etching, surface-brightening or pickling compositions
    • C09K13/02—Etching, surface-brightening or pickling compositions containing an alkali metal hydroxide
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0236—Special surface textures
    • H01L31/02363—Special surface textures of the semiconductor body itself, e.g. textured active layers

Definitions

  • the present invention relates to an etching composition for texturing a crystalline silicon-based wafer.
  • Solar cells are photocells that convert solar energy into electric energy.
  • photocells include selenium photocells based on contact of a metal and a semiconductor, copper sulfite photocells, and silicon photocells based on the principle of a PN semiconductor.
  • the silicon photocell is manufactured having silicon doped with boron as the basis of the P-type silicon semiconductor and diffuse phosphorus on the surface of the P-type silicon semiconductor, thereby having to form a PN junction semiconductor substrate comprised of a N-type silicon semiconductor.
  • light such as solar light is radiated onto the substrate where an electric field is formed by the PN junction, electrons (-) and holes (+) in the semiconductor are excited and thus may freely move in the semiconductor.
  • the electrons (-) reach an N-type semiconductor and the holes (+) reach a P-type semiconductor.
  • Electrodes are formed on the surfaces of the P-type and N-type semiconductors to allow electrons to flow through an external circuit, so that current is generated. Based on such a principle, solar energy is converted into electric energy.
  • the absorption of light should be increased to the maximum extent as possible.
  • the surface of a silicon wafer for a solar cell is formed into a fine pyramidal structure and then subjected to ant i-reflect ion treatment.
  • the surface of the silicon textured with the fine pyramidal structure may lower the reflectance of incident light over a wide wavelength range, thus increasing the intensity of already absorbed light, thereby enhancing performance, namely, conversion efficiency, of a solar cell.
  • Thorough research and development into forming fine pyramidal surface structures is ongoing, and specific examples thereof are described below.
  • US Patent No. 4,137,123 discloses a silicon texture etching solution obtained by dissolving 0.5 ⁇ 10 wt% of silicon in an anisotropic etchant comprising 0 - 75 wt% of ethylene-glycol , 0.05 ⁇ 50 wt% of potassium hydroxide, and a remainder of deionized distilled water.
  • European Patent No. 0477424 discloses a texture etching method that includes subjecting a texture etching solution in which silicon has been dissolved in ethyleneglycol , potassium hydroxide and a remainder of deionized distilled water to an oxygen supply, namely, aerating, upon texturing.
  • the texture etching solution not only increases the probability of reducing the texture solution due to already dissolved silicon therein, but also has the disadvantage of having to mount/install an additional aerating device.
  • Korean Patent No. 0180621 discloses a texture etching solution comprising 0.5 ⁇ 5 vol of potassium hydroxide, 3.0 ⁇ 20 vol% of isopropyl alcohol, and 75 ⁇ 96.5 vol% of deionized water.
  • US Patent No. 6,451,218 discloses a texture etching solution comprising an alkaline compound, isopropanol, an aqueous alkaline ethyleneglycol , and a remainder of deionized distilled water.
  • the texture etching solution is problematic because isopropyl alcohol, which has a low boiling point, should be additionally added during texturing and thus used in a larger amount, undesirably lowering productivity and negating economic benefits.
  • a portion on which a fine pyramidal structure has not been formed may be partially created, undesirably deteriorating the texture uniformity of the silicon wafer.
  • the present invention provides an etching composition for texturing a crystalline silicon-based wafer, which enables a fine pyramidal structure to be uniformly formed on the surface of the crystalline silicon-based wafer so as to achieve efficient light absorption.
  • the present invention provides an etching composition for texturing a crystalline silicon-based wafer, which comprises a high-boiling-point cyclic compound and is thus able to increase the number of processing sheets even when used in a considerably reduced amount compared to when using conventional texture etching compositions.
  • the present invention provides an etching composition for texturing a crystalline silicon-based wafer, which obviates needs for additional silicon particles, an aerating process (an oxygen supply process) or the addition of a chemical during the process, in order to form a fine pyramidal structure.
  • An aspect of the present invention provides an etching composition for texturing a crystalline silicon-based wafer, comprising (A) 0.1 ⁇ 20 wt of at least one alkaline compound, (B) 0.1 - 50 wt% of at least one cyclic compound having a boiling point of 100 ⁇ 400 ° C, and (C) a remainder of water, based on the total weight of the composition.
  • an etching composition for texturing a crystalline silicon-based wafer can form a uniform fine pyramidal structure on the surface of a silicon wafer, thus maximizing the absorption of light. Also, according to the present invention, the etching composition for texturing a crystalline silicon-based wafer can remarkably increase the number of processing sheets compared to when using conventional texture etching compositions, thus generating economic benefits. Also, according to the present invention, the etching composition for texturing a crystalline silicon-based wafer obviates the needs for addition of a chemical during texturing or the use of an additional aerating device, and is thus very advantageous in terms of initial production cost, process cost, and formation of a uniform fine pyramidal structure.
  • FIG. 1 is an optical microscope image showing the texture of a single- crystal silicon wafer using an etching composition for texturing a crystalline silicon-based wafer of Example 4;
  • FIG. 2 is a scanning electron microscope (SEM) image showing the surface of a single-crystal silicon wafer textured using the etching composition for texturing a crystalline silicon-based wafer of Example 4;
  • FIG. 3 is an SEM image showing the cross-section of a single-crystal silicon wafer textured using the etching composition for texturing a crystalline silicon-based wafer of Example 4.
  • an etching composition for texturing a crystalline silicon-based wafer comprises (A) at least one alkaline compound, (B) at least one cyclic compound, and (C) water.
  • the (A) at least one alkaline compound is used in an amount of 0.1 ⁇ 20 wt , preferably 1 - 5 wt , based on the total weight of the composition. If the amount of this component is within the above range, etching of silicon surface may be easily carried out.
  • the (A) at least one alkaline compound is preferably selected from the group consisting of potassium hydroxide (KOH), sodium hydroxide, ammonium hydroxide, tetrahydroxymethyl ammonium and tetrahydroxyethyl ammonium. Particularly Useful is potassium hydroxide or sodium hydroxide.
  • the (B) at least one cyclic compound has a boiling point of 100 ⁇ 400 ° C.
  • the isopropyl alcohol (IPA) that is typically used upon texturing has a low boiling point (82 ° C) and thus the ratio of K0H/IPA may vary during the texturing process (process temperature: 75 ⁇ 85 ° C), undesirably increasing the probability of adversely affecting the. quality of the texture.
  • the boiling point of the cyclic compound should fall within the above range.
  • the cyclic compound indicates a C 4 ⁇ C 10 heterocyclic compound comprising one or more heterogeneous elements selected from among N, 0 and S.
  • the (B) at least one cyclic compound is used in an amount of 0.1 ⁇ 50 wt%, preferably 2 - 10 wt% based on the total weight of the composition. If the amount of this component falls within the above range, the cyclic compound functions to improve the surface wettability of crystalline silicon so as to prevent over-etching by an alkaline compound, thus allowing a uniform fine pyramidal structure to be formed. Also, the etched and dissolved hydrogen bubbles may have been rapidly reduced, thus prevent the generation of a bubble stick phenomenon.
  • the (B) at least one cyclic compound is preferably selected from the group consisting of piperazine-based compound, morphol ine-based compound, pyridine-based compound, piper idine-based compound, piperidone-based compound, pyrrol idine-based compound, pyrrol idone-based compound, imidazolidinone-based compound, furan-based compound, aniline- based compound, toluidine-based compound and lactone-based compound.
  • cyclic compound having a boiling point of 100 ⁇ 400 ° C include piperazine, N-methylpiperazine, N-ethylpiperazine, hydroxyethylpiperazine, N-(2-aminoethyl)piperazine, ⁇ , ⁇ ' - dimethylpiperazine, morphol ine, N-methylmorpholine, N-ethylmorpholine, N-phenylmorpholine, N-cocomorpholine, N-(2-aminoethyl)morpholine, N-(2- cyanethyDmorpholine, N-(2-hydroxyethyl)morpholine, N-(2- hydroxypropyOmorpholine, N-ethylmorpholine, N-acetylmorpholine, N- formylmorpholine, N-methylmorpholine-N-oxide, pyridine, 3- hydroxypyridine, 2-pyridineethanol , picoline, N-methylpiperidine, 3,5- dimethylpiperidine
  • the remaining amount is composed of (C) water such that the total weight of the composition is 100%.
  • the water used is preferably deionized distilled water which is adapted for semiconductor processing and has a resistivity of 18 ⁇ ⁇ cm or more.
  • the etching composition for texturing a crystalline silicon-based wafer according to the present invention may be applied to any of dipping-, spraying- and single sheet processing-type etching processes.
  • Etching compositions for texturing a crystalline silicon-based wafer were prepared from components in the amounts shown in Table 1 below. [TABLE 1]
  • KOH potassium hydroxide
  • NaOH sodium hydroxide
  • NMP N-methylpyrrolidone
  • NMP-1 N-methylpiperazine
  • NMM N-methylmorphol ine
  • NMP-2 N-methylpiperidine
  • NMP-3 N-methylpiperidone
  • NMI N-methyl imidazol idinone
  • IPA isopropyl alcohol
  • EG ethyleneglycol
  • MEA monoethanolamine
  • AEP N-(2-aminoethyl)piperazine
  • a single-crystal silicon wafer was immersed in the etching composition for texturing a crystalline silicon-based wafer of each of Examples 1 ⁇
  • the average texture pyramid size and reflectance of the single-crystal silicon wafer using the etching composition of Comparative Example 1 are not greatly different from those when using the etching compositions of Examples 1 - 12.
  • the etching composition of Comparative Example 1 is problematic because IPA should be continuously added during the texturing process due to its low boiling point, and also because the temperature of the chemical may vary depending on the additional use of IPA, undesirably resulting in a non-uniform texture.
  • cost may increase.
  • FIG. 1 is an image from an optical microscope showing the texture of the single-crystal silicon wafer using the etching composition for texturing a crystalline silicon-based wafer of Example 4.
  • FIG. 2 is an SEM image showing the surface of the single-crystal silicon wafer textured using the etching composition for texturing a crystalline silicon-based wafer of Example 4.
  • FIG. 3 is an SEM image showing the cross-section of the single-crystal silicon wafer textured using the etching composition for texturing a crystalline silicon-based wafer of Example 4.
  • pyramids can be seen to have been formed over the entire surface of the wafer.
  • 1 is the length of the base of the pyramid and 2 is the height of the pyramid.

Abstract

Disclosed is an etching composition for texturing a crystalline silicon-based wafer, including (A) 0.1 ~ 20 wt% of at least one alkaline compound, (B) 0.1 ~ 50 wt% of at least one cyclic compound having a boiling point of 100 ~ 400°C, and (C) the remainder of water, based on the total weight of the composition.

Description

DESCRIPTION
Invention Title: ETCHING COMPOSmON FOR TEXTURING CRYSTALLINE SIUCON-BASED WAFER
Technical Field
The present invention relates to an etching composition for texturing a crystalline silicon-based wafer.
The present invention claims the benefit of Korean Patent Application No. 10-2009-0101698, filed on October 26, 2009, which is hereby incorporated by reference in its entirety into this specification.
Background Art
Solar cells are photocells that convert solar energy into electric energy. Examples of photocells include selenium photocells based on contact of a metal and a semiconductor, copper sulfite photocells, and silicon photocells based on the principle of a PN semiconductor. The silicon photocell is manufactured having silicon doped with boron as the basis of the P-type silicon semiconductor and diffuse phosphorus on the surface of the P-type silicon semiconductor, thereby having to form a PN junction semiconductor substrate comprised of a N-type silicon semiconductor. In case where light such as solar light is radiated onto the substrate where an electric field is formed by the PN junction, electrons (-) and holes (+) in the semiconductor are excited and thus may freely move in the semiconductor. In such an electric field formed by the PN junction, the electrons (-) reach an N-type semiconductor and the holes (+) reach a P-type semiconductor. Electrodes are formed on the surfaces of the P-type and N-type semiconductors to allow electrons to flow through an external circuit, so that current is generated. Based on such a principle, solar energy is converted into electric energy. Hence, in order to maximize the electrical output per unit area of the silicon photocell, the absorption of light should be increased to the maximum extent as possible. To this end, the surface of a silicon wafer for a solar cell is formed into a fine pyramidal structure and then subjected to ant i-reflect ion treatment. The surface of the silicon textured with the fine pyramidal structure may lower the reflectance of incident light over a wide wavelength range, thus increasing the intensity of already absorbed light, thereby enhancing performance, namely, conversion efficiency, of a solar cell. Thorough research and development into forming fine pyramidal surface structures is ongoing, and specific examples thereof are described below.
US Patent No. 4,137,123 discloses a silicon texture etching solution obtained by dissolving 0.5 ~ 10 wt% of silicon in an anisotropic etchant comprising 0 - 75 wt% of ethylene-glycol , 0.05 ~ 50 wt% of potassium hydroxide, and a remainder of deionized distilled water. In addition, European Patent No. 0477424 discloses a texture etching method that includes subjecting a texture etching solution in which silicon has been dissolved in ethyleneglycol , potassium hydroxide and a remainder of deionized distilled water to an oxygen supply, namely, aerating, upon texturing. However, the texture etching solution, not only increases the probability of reducing the texture solution due to already dissolved silicon therein, but also has the disadvantage of having to mount/install an additional aerating device.)
Korean Patent No. 0180621 discloses a texture etching solution comprising 0.5 ~ 5 vol of potassium hydroxide, 3.0 ~ 20 vol% of isopropyl alcohol, and 75 ~ 96.5 vol% of deionized water. Furthermore, US Patent No. 6,451,218 discloses a texture etching solution comprising an alkaline compound, isopropanol, an aqueous alkaline ethyleneglycol , and a remainder of deionized distilled water. However, the texture etching solution is problematic because isopropyl alcohol, which has a low boiling point, should be additionally added during texturing and thus used in a larger amount, undesirably lowering productivity and negating economic benefits. Furthermore, because of the temperature gradient generated when texturing, a portion on which a fine pyramidal structure has not been formed may be partially created, undesirably deteriorating the texture uniformity of the silicon wafer.
Although cases have been introduced where a hot concentrated hydrazine solution is used in addition to the texture etching solution or where dry etching is performed using a fluorine-containing compound or oxygen, the use of these is restricted for environmental or monetary reasons. Disclosure
Technical Problem
Accordingly, the present invention provides an etching composition for texturing a crystalline silicon-based wafer, which enables a fine pyramidal structure to be uniformly formed on the surface of the crystalline silicon-based wafer so as to achieve efficient light absorption.
Also the present invention provides an etching composition for texturing a crystalline silicon-based wafer, which comprises a high-boiling-point cyclic compound and is thus able to increase the number of processing sheets even when used in a considerably reduced amount compared to when using conventional texture etching compositions.
Also, the present invention provides an etching composition for texturing a crystalline silicon-based wafer, which obviates needs for additional silicon particles, an aerating process (an oxygen supply process) or the addition of a chemical during the process, in order to form a fine pyramidal structure.
Technical Solution
An aspect of the present invention provides an etching composition for texturing a crystalline silicon-based wafer, comprising (A) 0.1 ~ 20 wt of at least one alkaline compound, (B) 0.1 - 50 wt% of at least one cyclic compound having a boiling point of 100 ~ 400°C, and (C) a remainder of water, based on the total weight of the composition.
Advantageous Effects
According to the present invention, an etching composition for texturing a crystalline silicon-based wafer can form a uniform fine pyramidal structure on the surface of a silicon wafer, thus maximizing the absorption of light. Also, according to the present invention, the etching composition for texturing a crystalline silicon-based wafer can remarkably increase the number of processing sheets compared to when using conventional texture etching compositions, thus generating economic benefits. Also, according to the present invention, the etching composition for texturing a crystalline silicon-based wafer obviates the needs for addition of a chemical during texturing or the use of an additional aerating device, and is thus very advantageous in terms of initial production cost, process cost, and formation of a uniform fine pyramidal structure.
Description of Drawings
FIG. 1 is an optical microscope image showing the texture of a single- crystal silicon wafer using an etching composition for texturing a crystalline silicon-based wafer of Example 4;
FIG. 2 is a scanning electron microscope (SEM) image showing the surface of a single-crystal silicon wafer textured using the etching composition for texturing a crystalline silicon-based wafer of Example 4; and
FIG. 3 is an SEM image showing the cross-section of a single-crystal silicon wafer textured using the etching composition for texturing a crystalline silicon-based wafer of Example 4.
Best Mode
Hereinafter, a detailed description will be given of the present invention.
According to the present invention, an etching composition for texturing a crystalline silicon-based wafer comprises (A) at least one alkaline compound, (B) at least one cyclic compound, and (C) water.
In the etching composition for texturing a crystalline silicon-based wafer according to the present invention, the (A) at least one alkaline compound is used in an amount of 0.1 ~ 20 wt , preferably 1 - 5 wt , based on the total weight of the composition. If the amount of this component is within the above range, etching of silicon surface may be easily carried out.
Also, the (A) at least one alkaline compound is preferably selected from the group consisting of potassium hydroxide (KOH), sodium hydroxide, ammonium hydroxide, tetrahydroxymethyl ammonium and tetrahydroxyethyl ammonium. Particularly Useful is potassium hydroxide or sodium hydroxide.
In the etching composition for texturing a crystalline silicon-based wafer according to the present invention, the (B) at least one cyclic compound has a boiling point of 100 ~ 400°C. The isopropyl alcohol (IPA) that is typically used upon texturing has a low boiling point (82°C) and thus the ratio of K0H/IPA may vary during the texturing process (process temperature: 75 ~ 85°C), undesirably increasing the probability of adversely affecting the. quality of the texture. In order to prevent such adverse effects from occurring, the boiling point of the cyclic compound should fall within the above range.
As used herein, the cyclic compound indicates a C4 ~ C10 heterocyclic compound comprising one or more heterogeneous elements selected from among N, 0 and S.
Furthermore, the (B) at least one cyclic compound is used in an amount of 0.1 ~ 50 wt%, preferably 2 - 10 wt% based on the total weight of the composition. If the amount of this component falls within the above range, the cyclic compound functions to improve the surface wettability of crystalline silicon so as to prevent over-etching by an alkaline compound, thus allowing a uniform fine pyramidal structure to be formed. Also, the etched and dissolved hydrogen bubbles may have been rapidly reduced, thus prevent the generation of a bubble stick phenomenon. As such, the (B) at least one cyclic compound is preferably selected from the group consisting of piperazine-based compound, morphol ine-based compound, pyridine-based compound, piper idine-based compound, piperidone-based compound, pyrrol idine-based compound, pyrrol idone-based compound, imidazolidinone-based compound, furan-based compound, aniline- based compound, toluidine-based compound and lactone-based compound. Specific examples of the cyclic compound having a boiling point of 100 ~ 400°C include piperazine, N-methylpiperazine, N-ethylpiperazine, hydroxyethylpiperazine, N-(2-aminoethyl)piperazine, Ν,Ν' - dimethylpiperazine, morphol ine, N-methylmorpholine, N-ethylmorpholine, N-phenylmorpholine, N-cocomorpholine, N-(2-aminoethyl)morpholine, N-(2- cyanethyDmorpholine, N-(2-hydroxyethyl)morpholine, N-(2- hydroxypropyOmorpholine, N-ethylmorpholine, N-acetylmorpholine, N- formylmorpholine, N-methylmorpholine-N-oxide, pyridine, 3- hydroxypyridine, 2-pyridineethanol , picoline, N-methylpiperidine, 3,5- dimethylpiperidine, N-ethylpiperidine, N-(2-hydroxyethyl)piperidine, N- methyl-4-piperidone, N-vinyl-2- iperidone, N-methylpyrrolidine, N-ethyl- 2-pyrrolidone, N-isopropyl-2-pyrrolidone, N-butyl-2-pyrrolidone, N- tert-butyl-2-pyrrol idone, N-hexyl-2-pyrrol idone, N-octyl-2-pyrrol idone, N-benzyl-2-pyrrolidone, N-cyclohexyl-2-pyrrol idone, N-vinyl-2- pyrrol idone, N-(2-hydroxyethyl )-2-pyrrol idone, N-(2-methoxyethyl )-2- pyrrol idone, N-(2-methoxypropyl )-2-pyrrol idone, N-(2~ethoxyethyl )-2- pyrrol idone, N-methylimidazolidinone, dimethyl imidazolidinone, N-(2- hydroxyethyD-ethyleneurea, tetrahydrofuran, tetrahydrofurfuryl alcohol, N-methylaniline, N-ethylaniline, N,N-dimethylaniline, N-(2- hydroxyethyl )ani 1 ine, N,N-bis-(2-hydroxyethyl )ani 1 ine, N-ethyl-N-(2- hydroxyethyl )ani 1 ine, N,N-N-ethyl-o-toluidine, N-ethyl-N-(2- hydroxyethyl)-m-toluidine, dimethylbenzylamine, γ-butyrolactone, tolyltriazole, 1,2,3-benzotriazole, 1,2,3-triazole, 1,2,4-triazole, 3- amino-l,2,4-triazole, 4-amino-4H-l,2,4-triazole, 1-hydroxybenzotriazole, 1-methylbenzotriazole, 2-methylbenzotriazole, 5-methylbenzotriazole, benzotriazole-5-carboxylic acid, nitrobenzotriazole and 2-(2H- benzotriazol-2-yl )-4,6-di-t-butylphenol .
In the etching composition for texturing a crystalline silicon-based wafer according to the present invention, the remaining amount is composed of (C) water such that the total weight of the composition is 100%. As such, the water used is preferably deionized distilled water which is adapted for semiconductor processing and has a resistivity of 18 ΜΩ · cm or more.
The etching composition for texturing a crystalline silicon-based wafer according to the present invention may be applied to any of dipping-, spraying- and single sheet processing-type etching processes.
Mode for Invention
The following examples are set forth to illustrate, but are not to be construed as limiting the present invention, and may provide a better understanding of the present invention.
EXAMPLES 1 ~ 12 and COMPARATIVE EXAMPLES 1 ~ 4: Preparation of Etching
Composition for Texturing Crystalline Silicon-based Wafer
Etching compositions for texturing a crystalline silicon-based wafer were prepared from components in the amounts shown in Table 1 below. [TABLE 1]
Alkal ine Cyclic Compound Water
Figure imgf000011_0001
[Note]
KOH: potassium hydroxide NaOH: sodium hydroxide NMP: N-methylpyrrolidone NMP-1: N-methylpiperazine NMM: N-methylmorphol ine NMP-2: N-methylpiperidine NMP-3: N-methylpiperidone NMI : N-methyl imidazol idinone IPA: isopropyl alcohol EG: ethyleneglycol
BDG: butyldiglycol
MEA: monoethanolamine AEP: N-(2-aminoethyl)piperazine
AM: N-(2-aminoethyl)morpholine
TEST EXAMPLE: Evaluation of Properties of Etching Composition for
Texturing Crystal 1 ine Si 1 icon-based Wafer
Evaluation of Texture Uniformity>
A single-crystal silicon wafer was immersed in the etching composition for texturing a crystalline silicon-based wafer of each of Examples 1 ~
12 and Comparative Examples 1 - 4. As such, texturing was performed under conditions of 80°C and 30 min. The texture uniformity of each composition was evaluated with the naked eye (digital camera), optical microscope, SEM or the like, and the size of pyramids was measured using
SEM. An average reflectance was measured when UV light having a wavelength range of 400 ~ 800 ran was radiated. The results are shown in
Table 2 below and FIGS. 1 to 3.
[TABLE 2]
Figure imgf000012_0001
Chemical Discoloring
Texture uniformity
®: formation of pyramids over the entire surface of wafer
O- formation of pyramids on part of wafer (the degree of forming no pyramidal structure is less than 5%)
Δ: formation of pyramids on part of wafer (the degree of forming no pyramidal structure is 5 ~ 50%)
X: formation of no pyramids on the wafer (the degree of forming no pyramidal structure is more than 50%)
The term "chemical discoloring" indicates that there was no need for a texture test due to the spontaneous change with time upon heating to the texturing temperature.
As is apparent from Table 2, the texture uniformity of the single- crystal silicon wafer using the etching compositions of Examples 1 - 12 can be seen to be superior.
The average texture pyramid size and reflectance of the single-crystal silicon wafer using the etching composition of Comparative Example 1 are not greatly different from those when using the etching compositions of Examples 1 - 12. However, the etching composition of Comparative Example 1 is problematic because IPA should be continuously added during the texturing process due to its low boiling point, and also because the temperature of the chemical may vary depending on the additional use of IPA, undesirably resulting in a non-uniform texture. Furthermore, when the texturing is carried out, cost may increase.
Also, when using the etching composition of Comparative Example 2, texture uniformity and reflectance are considerably different from those when using the etching compositions of Examples 1 - 12. In addition, the etching compositions of Comparative Examples 3 and 4 cannot be applied to the texturing process attributable to chemical discoloring. FIG. 1 is an image from an optical microscope showing the texture of the single-crystal silicon wafer using the etching composition for texturing a crystalline silicon-based wafer of Example 4. FIG. 2 is an SEM image showing the surface of the single-crystal silicon wafer textured using the etching composition for texturing a crystalline silicon-based wafer of Example 4. FIG. 3 is an SEM image showing the cross-section of the single-crystal silicon wafer textured using the etching composition for texturing a crystalline silicon-based wafer of Example 4.
With reference to FIGS. 1 to 3, pyramids can be seen to have been formed over the entire surface of the wafer. Wherein, 1 is the length of the base of the pyramid and 2 is the height of the pyramid.

Claims

An etching composition for texturing a crystalline silicon- based wafer, comprising, based on total weight of the composition:
(A) 0.1 ~ 20 wt of at least one alkaline compound;
(B) 0.1 ~ 50 wt% of at least one cyclic compound having a boiling point of 100 ~ 400°C; and
(C) the remainder of water.
The etching composition according to claim 1, comprising, based on the total weight of the composition:
(A) 1 - 5 wt% of the at least one alkaline compound;
(B) 2 - 10 wt% of the at least one cyclic compound having a boiling point of 100 - 400°C; and
(C) the remainder of water.
The etching composition according to claim 1, wherein the (A) at least one alkaline compound is selected from the group consisting of potassium hydroxide, sodium hydroxide, ammonium hydroxide, tetrahydroxymethyl ammonium, and tetrahydroxyethyl ammonium.
The etching composition according to claim 1, wherein the (B) at least one cyclic compound having a boiling point of 100 ~ 400°C is selected from the group consisting of piperazine, N- methylpiperazine, N-ethylpiperazine, hydroxyethylpiperazine, N-(2-aminoethyl)piperazine, Ν,Ν' -dimethylpiperazine, morpholine, N-methylmorphol ine, N-ethylmorpholine, N- pheny1morpho1 ine, N-cocomorpho1 ine, N-(2- aminoethyl )morphol ine, N-(2-cyanethyl )morphol ine, N-(2- hydroxyethyOmorpholine, N-(2-hydroxypropyl)raorpholine, N- ethylmorpholine, N-acetylraorpholine, N-formylmorpholine, N- raethylmorpholine-N-oxide, pyridine, 3-hydroxypyridine, 2- pyridineethanol , picoline, N-raethylpiperidine, 3,5- dimethylpiperidine, N-ethylpiperidine, N-(2- hydroxyethyOpiperidine, N-methyl-4-piperidone, N-vinyl-2- piperidone, N-methylpyrrolidine, N-ethyl-2-pyrrolidone, N- isopropyl-2-pyrrolidone, N-buty1-2-pyrrolidone, N-tert-butyl- 2-pyrrolidone, N-hexyl-2-pyrrol idone, N-octyl-2-pyrrolidone, N-benzyl-2-pyrrolidone, N~cyclohexyl-2-pyrrol idone, N-vinyl-2- pyrrol idone, N-(2-hydroxyethyl)-2-pyrrol idone, N-(2- methoxyethy1 )-2-pyrro1 idone, N-(2-methoxypropy1)-2- pyrrol idone, N-(2-ethoxyethyl )-2-pyrrol idone, N- methylimidazolidinone, dimethyl imidazolidinone, N-(2- hydroxyethyl )-ethyleneurea, tetrahydrofuran, tetrahydrofurfuryl alcohol, N-methylani 1 ine, N-ethylaniline, N,N-dimethylaniline, N-(2-hydroxyethyl)aniline, N,N~bis-(2- hydroxyethyDaniline, N-ethyl-N-(2-hydroxyethyl)aniline, N,N- N-ethyl-o-toluidine, N-ethyl-N-(2-hydroxyethyl )-m-toluidine, dimethylbenzylamine, y-butyrolactone, tolyltriazole, 1,2,3- benzotriazole, 1,2,3-triazole, 1,
2,4-triazole,
3-amino-l,2,4- triazole, 4-araino-4H-l,2,
4-triazole, 1-hydroxybenzotriazole, 1-methylbenzotriazole, 2-methylbenzotriazole, 5- methylbenzotriazole, benzotriazole-5-carboxylic acid, nitrobenzotriazole and 2-(2H-benzotriazol-2-yl)-4,6-di-t- butylphenol .
5. A method of texture etching a crystalline silicon, by either or both dipping and/or spraying at 50 ~ 100°C for a period of time ranging from 30 sec to 60 min using the etching composition of claim 1.
PCT/KR2010/007323 2009-10-26 2010-10-25 Etching composition for texturing crystalline silicon-based wafer WO2011052941A2 (en)

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CN103890139A (en) * 2011-10-19 2014-06-25 东友精细化工有限公司 Texture etching solution composition and texture etching method of crystalline silicon wafers
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