WO2012144461A1

WO2012144461A1 - Etching liquid composition and etching method

Info

Publication number: WO2012144461A1
Application number: PCT/JP2012/060276
Authority: WO
Inventors: 木村　真弓; 篤史松井; 哲弥後藤; 次広田湖
Original assignee: 林純薬工業株式会社
Priority date: 2011-04-19
Filing date: 2012-04-16
Publication date: 2012-10-26
Also published as: JP2012227304A; TW201305318A

Abstract

This etching liquid composition for forming a recessed and projected shape by etching the surface of a single crystal silicon substrate contains an alkaline compound, an organic solvent, and a surfactant.

Description

Etching solution composition and etching method

The present invention relates to an etching solution composition and an etching method, and in particular, forms a fine pyramidal uneven shape (hereinafter sometimes referred to as “texture”) by etching the surface of single crystal silicon. The present invention relates to an etching solution composition and an etching method.

Solar cells are attracting attention as a safe and environmentally friendly energy source because they can directly convert sunlight energy into electricity. Although there are various types of solar cells, a solar cell using a single crystal silicon substrate can be given as one that is for general use and has the highest conversion efficiency. A solar cell using a single crystal silicon substrate is one of the mainstreams in the field of development of currently used solar cells.

Developed solar cells have been actively developed to increase the conversion efficiency for converting sunlight into electricity. One way to increase the conversion efficiency of converting light into electricity is to improve the antireflection efficiency on the surface of the single crystal silicon substrate, by wet etching, a fine pyramidal uneven shape called texture on the surface of the single crystal silicon substrate Is formed. If such a texture is formed on the surface of the single crystal silicon substrate, the reflectance of the surface of the single crystal silicon substrate can be lowered by causing multiple reflection of received light on the surface of the single crystal silicon substrate. Then, more light can be confined on the surface of the single crystal silicon substrate, and as a result, a large amount of light that can be converted into electricity can be secured.

In recent years, there is a tendency to reduce the thickness of the silicon substrate from the viewpoint of reducing the silicon material per single crystal silicon substrate and reducing the cost. Under such circumstances, efficient confinement of light by the texture formed on the surface of the single crystal silicon substrate becomes increasingly important.

Here, techniques for forming a texture on the surface of a silicon substrate are disclosed in Japanese Patent Application Laid-Open No. 61-96772 (Patent Document 1), Japanese Patent Application Laid-Open No. 2000-1792 (Patent Document 2), and Japanese Patent Application Laid-Open No. 11-233484 ( Patent Literature 3), Japanese Patent Laid-Open No. 2002-57139 (Patent Literature 4), WO 2006/046601 (Patent Literature 5), Japanese Patent Laid-Open No. 2010-74102 (Patent Literature 6), Japanese Patent Laid-Open No. 2010-93194 ( Patent Document 7) and Japanese Patent Application Laid-Open No. 2010-141139 (Patent Document 8).

JP 61-96772 A JP 2000-1792 A Japanese Patent Laid-Open No. 11-233484 JP 2002-57139 A WO2006 / 046601 Publication JP 2010-74102 A JP 2010-93194 A JP 2010-141139 A

According to Patent Document 1, a technique is disclosed in which an etching solution containing sodium hydroxide and isopropyl alcohol is heated to 80 ° C. to 90 ° C., and a texture is formed on the surface by bubbling or rocking.

According to Patent Document 2, an etching solution containing at least water, an alkaline reagent, and at the same time isopropanol and an aqueous alkaline ethylene glycol solution is disclosed.

According to Patent Document 3, an uneven substrate having an uneven structure is manufactured using an alkaline solution containing a surfactant.

According to Patent Document 4, a concavo-convex substrate is produced by containing a surfactant mainly composed of caprylic acid or lauric acid in an alkaline solution.

According to Patent Document 5, when forming the concavo-convex structure, the alkalinity includes at least one selected from the group consisting of carboxylic acids having at least one carboxyl group in one molecule and having 1 to 12 carbon atoms and salts thereof. Etching solution is used.

According to Patent Document 6, when unevenness is formed on the surface of a silicon substrate, water, an alkaline reagent, and X— (OH) _n (X is a saturated or unsaturated hydrocarbon group having 4 to 7 carbon atoms, n Uses an etching solution containing an alcohol derivative having an integer of 1 or more and n <Cn).

According to Patent Document 7, an etching process is performed using an etchant containing an alcohol solvent having a boiling point of 100 ° C. or higher and an alkaline aqueous solution.

According to Patent Document 8, one molecule has one or more hydroxyl groups, the solubility parameter is in the range of 8.0 to 13.0 (cal / cm ³ ) ^0.5 , and the boiling point at atmospheric pressure. An aqueous solution containing a compound at 95 ° C. or higher and an alkali hydroxide is used as an etching solution for forming irregularities.

Here, even when the etching solutions disclosed in Patent Documents 1 to 8 are used, a texture may not be formed appropriately. That is, the etching solutions disclosed in Patent Documents 1 to 8 are insufficient as the ability to form a texture.

Important things in the formation of an appropriate texture include in-plane uniformity within the same plane and the formation of an appropriate texture shape. In-plane uniformity means that there is almost no region where no texture is formed in the same surface of the silicon substrate that is the substrate to be processed, and the texture is formed uniformly over the entire surface. In addition, with regard to the appropriate shape of the texture, it can be said that a texture with an appropriate shape is formed if the unevenness in texture formation is insufficient, or if the uneven shape is largely uneven in the same plane. There is nothing.

Furthermore, the texture formation state may differ depending on the target silicon substrate. Specifically, for example, the silicon substrate before the etching treatment is sliced with a free abrasive grain type or fixed abrasive grain type wire saw. When etching a silicon substrate having a surface sliced in this way, when using an etching solution disclosed in the above-mentioned patent document, for a silicon substrate sliced using loose abrasive grains, Although a texture can be appropriately formed, there are some silicon substrates that are sliced using fixed abrasive grains that cannot be appropriately textured. Furthermore, there may be a case where a texture cannot be formed properly even on a silicon substrate smoothed by primary etching.

An object of the present invention is to provide an etching solution composition capable of reliably forming a texture having an appropriate shape.

Another object of the present invention is to provide an etching method capable of reliably forming a texture having an appropriate shape.

The inventors of the present application have the following two possible mechanisms for forming a texture: (1) the etching rate of the (111) surface of the silicon substrate is extremely slow relative to the (100) surface of the silicon substrate. And (2) a partial masking effect of the silicon substrate and an etching inhibiting effect when an additive having a hydrophobic group and a hydrophilic group is added. The following mechanism, which will be described later, was considered to be more important than the mechanism that does this.

That is, in the mechanism (1), it is appropriate to consider that anisotropic etching proceeds and texture is formed due to the difference in etching rate between the (100) plane of the silicon substrate and the (111) plane of the silicon substrate. It is. However, if the formation of the texture is caused by such a difference in etching rate, there is always such a difference in etching rate when an etching solution containing an alkali compound is used. Will be formed. Further, the texture should be formed regardless of the surface state of the silicon substrate, that is, the surface state of the silicon substrate sliced by using the above-described fixed abrasive type or loose abrasive type wire saw. However, in practice, a texture is not necessarily formed when an etching solution containing an alkali compound is used. Further, in the mechanism (2), even if there is a mask effect or the like due to the additive, the formation of texture due to the difference in etching rate between the (100) surface of the silicon substrate and the (111) surface of the silicon substrate. However, this is not always done properly.

Therefore, the inventors of the present application considered that the selectivity of the etching rate of the (110) plane of the silicon substrate to the etching rate of the (100) plane of the silicon substrate is important as a texture formation mechanism. That is, paying attention to the etching rate of the (100) plane of the silicon substrate and the etching rate of the (110) plane of the silicon substrate, it was considered that the texture can be appropriately formed by increasing the selectivity of this etching rate. .

Furthermore, the inventors of the present application also considered the mechanism by which the texture is formed as follows. The reaction formula for etching the surface of a silicon substrate using an alkali compound is as follows.

Si + 2OH ⁻ + 4H ₂ O → Si (OH) ₆ ²⁻ + 2H ₂ ↑

Here, if the hydrogen gas generated by the above-described etching reaction remains in a state where the hydrogen bubbles are attached to the surface of the silicon substrate, the etching reaction does not proceed on the surface where the bubbles are attached. As a result, a portion where no texture was formed was generated, and it was considered that in-plane uniformity during the formation of the texture was not ensured. Therefore, it was considered necessary to efficiently remove the hydrogen generated by the etching reaction from the surface of the silicon substrate.

In other words, the inventors of the present application increased the selectivity of the etching rate of the (110) surface of the silicon substrate to the (100) surface of the silicon substrate, and actively removed the hydrogen bubbles generated by the etching reaction. The liquid composition had the following configuration.

That is, the etching solution composition according to the present invention is an etching solution composition that forms an uneven shape by etching the surface of a single crystal silicon substrate, and includes an alkali compound, an organic solvent, and a surfactant.

According to such an etching solution composition, the selectivity of the etching rate of the (110) surface of the silicon substrate to the (100) surface of the silicon substrate can be increased, and hydrogen bubbles can be positively removed. . Moreover, a texture can be formed regardless of the surface state of the silicon substrate. Therefore, it is possible to reliably form an appropriately shaped texture.

That is, in the present invention, an alkaline compound, an organic solvent, and a surfactant are essential components as an etching solution composition. Then, using the etching solution composition according to the present invention, wet etching is performed on the surface of the single crystal silicon substrate, and a texture having an appropriate shape is reliably formed on the surface of the silicon substrate.

Preferably, the organic solvent includes at least one selected from the group consisting of glycol ethers, alcohols, nitrogen-containing organic solvents, and sulfur-containing organic solvents.

In a more preferred embodiment, the organic solvent is ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monobenzyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether. , Furfuryl alcohol, tetrahydrofurfuryl alcohol, N-methyl-2-pyrrolidone, dimethyl sulfoxide, and sulfolane.

The surfactant includes at least one selected from the group consisting of a fluorine-based anionic surfactant, a fluorine-based nonionic surfactant, a fluorine-based amphoteric surfactant, and a hydrocarbon-based anionic surfactant. You may comprise.

Further, the alkaline compound may include at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, and tetramethylammonium hydroxide.

More preferably, it contains silicon or a silicon compound.

In another aspect of the present invention, an etching method is an etching method for etching a surface of a single crystal silicon substrate to form a concavo-convex shape, and an etching solution composition containing an alkali compound, an organic solvent, and a surfactant. Etching is performed using an object.

According to such an etching method, the selectivity of the etching rate of the (110) surface of the silicon substrate relative to the (100) surface of the silicon substrate can be increased, and hydrogen bubbles can be positively removed. Moreover, a texture can be formed regardless of the surface state of the silicon substrate. Therefore, it is possible to reliably form an appropriately shaped texture.

The etching method according to the present invention is an etching method for etching a surface of a single crystal silicon substrate to form a concavo-convex shape, wherein the etching rate of the (100) plane of the silicon substrate and the (110) plane of the silicon substrate Etching is performed with a selection ratio, which is a ratio to the etching rate, of 3 or more.

Preferably, the single crystal silicon substrate is immersed in the etching solution composition and etched by wet etching.

More preferably, the single crystal silicon substrate includes at least one selected from the group consisting of a substrate sliced by a fixed abrasive method, a substrate sliced by a free abrasive method, and a substrate whose surface has undergone primary etching. Including.

According to such an etching solution composition and etching method, the selectivity of the etching rate of the (110) plane of the silicon substrate to the (100) plane of the silicon substrate can be increased, and hydrogen bubbles are actively removed. be able to. Moreover, a texture can be formed regardless of the surface state of the silicon substrate. Therefore, it is possible to reliably form an appropriately shaped texture.

It is a schematic sectional drawing which shows a part of single crystal silicon substrate which has a smooth plane. It is a schematic sectional drawing which shows a part of single crystal silicon substrate in which the texture of the appropriate shape was formed. 2 is a photograph showing the appearance of single crystal silicon according to Example 1. FIG. 10 is a photograph showing the appearance of single crystal silicon according to Comparative Example 5. 14 is a photograph showing the appearance of single crystal silicon according to Comparative Example 6. It is an electron micrograph which expands and shows the surface of the single crystal silicon concerning Example 1, and shows the case where magnification is 1000 times. It is an electron micrograph which expands and shows the surface of the single crystal silicon concerning Example 1, and shows the case where magnification is 2000 times. It is an electron micrograph which expands and shows the surface of the single crystal silicon concerning Example 2, and shows the case where magnification is 1000 times. It is an electron micrograph which expands and shows the surface of the single crystal silicon concerning Example 2, and shows the case where magnification is 2000 times. It is an electron micrograph which expands and shows the surface of single crystal silicon concerning comparative example 5, and shows the case where magnification is 1000 times. It is an electron micrograph which expands and shows the surface of single crystal silicon concerning comparative example 5, and shows the case where magnification is 2000 times. It is an electron micrograph which expands and shows the surface of single crystal silicon concerning comparative example 6, and shows the case where magnification is 1000 times. It is an electron micrograph which expands and shows the surface of single crystal silicon concerning comparative example 6, and shows the case where magnification is 2000 times.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing a part of a single crystal silicon substrate having a smooth plane. FIG. 1 is a diagram showing a state of a single crystal silicon substrate before so-called etching. FIG. 2 is a schematic cross-sectional view showing a part of a single crystal silicon substrate on which an appropriately shaped texture is formed. FIG. 2 is a diagram showing a state of the single crystal silicon substrate after etching is performed using the etching solution composition according to the present invention. For easy understanding, the uneven shape in FIG. 2 is exaggerated. Further, the texture formed on the surface of the actual silicon substrate does not have the uneven shape as shown in FIG. 2, and has some unevenness.

Referring to FIG. 1, before etching, surface 12 of single crystal silicon substrate 11 is smooth. As indicated by the arrows in FIG. 1, when the surface 12 is irradiated with light such as sunlight, most of the received light is reflected. In such a state, the effect of light confinement is small. Therefore, the efficiency of converting from light to electricity is low.

On the other hand, referring to FIG. 2, the silicon substrate 13 having an appropriate uneven shape on its surface, that is, the texture formed by the

slopes

14 and 15 of the cross section shown in FIG. In addition, it does not reflect much light. At least, the reflectance is lower than the surface 12 shown in FIG. Such a state has a high light confinement effect. Therefore, it is possible to convert light to electricity with high efficiency.

Here, the etching solution composition according to the present invention is an etching solution composition that forms an uneven shape as shown in FIG. 2 by etching the surface of the single crystal silicon substrate as shown in FIG. An alkali compound, an organic solvent, and a surfactant are included.

According to such an etching solution composition, it is possible to reliably form a texture having an appropriate shape. This will be described later.

The etching method according to the present invention is an etching method for forming a concavo-convex shape by etching the surface of a single crystal silicon substrate, and comprising an etching solution composition containing an alkali compound, an organic solvent, and a surfactant. And etching.

Here, examples of the alkali compound contained in the etching solution composition according to the present invention include sodium hydroxide, potassium hydroxide, and tetramethylammonium hydroxide. Preferably, sodium hydroxide and potassium hydroxide are used. Of course, a plurality of these alkali compounds may be used. Here, the alkali compound includes at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, and tetramethylammonium hydroxide.

The concentration of the alkali compound is not particularly limited as long as a desired etching shape can be obtained in actual use, and can be determined as appropriate. Here, when sodium hydroxide is used as an example, the concentration of sodium hydroxide is preferably 0.1 to 30% by weight.

Further, examples of the organic solvent contained in the etching solution composition according to the present invention include glycol ethers, alcohols, nitrogen-containing organic solvents, and sulfur-containing organic solvents. These organic solvents may be used as a single type, but of course, a plurality of types may be used. Here, the organic solvent includes at least one selected from the group consisting of glycol ethers, alcohols, nitrogen-containing organic solvents, and sulfur-containing organic solvents.

Specific examples of glycol ethers include ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monobenzyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether. Etc. Specific examples of alcohols include furfuryl alcohol and tetrahydrofurfuryl alcohol. Specific examples of the nitrogen-containing organic solvent include N-methyl-2-pyrrolidone. Specific examples of the sulfur-containing organic solvent include dimethyl sulfoxide, sulfolane and the like.

The concentration of the organic solvent is not particularly limited as long as a desired etching shape can be obtained in actual use, and can be determined as appropriate. Here, when diethylene glycol monobutyl ether is used as an example, the concentration of diethylene glycol monobutyl ether is preferably 0.001 to 10% by weight.

The surfactant contained in the etching solution composition according to the present invention includes a fluorine-based anionic surfactant, a fluorine-based nonionic surfactant, a fluorine-based amphoteric surfactant, and a hydrocarbon-based anionic surfactant. Etc. These surfactants may be of a single type, but of course, a plurality of types may be used. Here, the surfactant is at least one selected from the group consisting of a fluorine-based anionic surfactant, a fluorine-based nonionic surfactant, a fluorine-based amphoteric surfactant, and a hydrocarbon-based anionic surfactant. Including.

Specific examples of the fluorine-based anionic surfactant include perfluoroalkylsulfonic acid and its salt, perfluoroalkylcarboxylic acid and its salt, perfluoroalkylphosphonic acid and its salt, and the like. Specific examples of the fluorine-based nonionic surfactant include α-perfluorononenyloxy-ω-methyl polyethylene oxide, α-perfluorononenyloxy-ω-perfluorononenyl polyethylene oxide, and the like. Specific examples of the fluorine-based amphoteric surfactant include perfluoroalkylamine oxide, amphoteric fluorinated polymer, and perfluoroalkyl betaine. Specific examples of the hydrocarbon-based anionic surfactant include naphthalenesulfonic acid formalin condensate and salts thereof, phenylphenolsulfonic acid formalin condensate and salts thereof, polystyrene sulfonic acid and salts thereof, diethylhexylsulfosuccinic acid and salts thereof. Examples thereof include salts, polyacrylic acid and salts thereof. Preferably, a fluorine-based amphoteric surfactant such as perfluoroalkylamine oxide or an amphoteric fluorinated polymer is used.

As for the concentration of the surfactant, it may be any concentration as long as a desired etching shape can be obtained in actual use, and can be determined as appropriate. Here, as an example, the concentration of the surfactant is preferably 1 ppm (parts per million) to 5% by weight. In addition, although it shows for confirmation, 1 ppm = 0.0001 wt%.

Furthermore, the etching solution composition according to the present invention may contain silicon or a silicon compound. That is, the etching solution composition according to the present invention contains silicon or a silicon compound. According to such a configuration, it is considered that the etching rate of the silicon substrate (110) surface can be controlled and the etching rate of the silicon substrate (100) surface can be stabilized.

Specific examples of silicon or silicon compound include metal silicon, silicon dioxide, sodium silicate, potassium silicate, and the like.

In addition, the etching with the etching solution composition according to the present invention is not only a silicon substrate sliced by free abrasive grains, which is generally said to be easy to form a texture, but is generally said to be difficult to form a texture. The present invention can also be applied to a silicon substrate sliced with abrasive grains. That is, regardless of whether the silicon substrate is sliced by the free abrasive grain method or the silicon substrate sliced by the fixed abrasive grain method, the etching with the etching solution composition according to the present invention has an appropriate shape. A texture can be reliably formed. Furthermore, a smooth surface after removing a damage layer on the surface, which is generally said to be difficult to form a texture, specifically, for example, a surface obtained by first etching the surface with an alkali such as NaOH. Can be applied.

Note that an etching solution composition having such a composition can be provided in a concentrated state. The ability to circulate in such a form is advantageous from the viewpoint of reducing the chemical cost.

Here, the etching mechanism by the etching solution composition according to the present invention is considered as follows. That is, the etching solution composition according to the present invention is configured to include an alkali compound, an organic solvent, and a surfactant. Of these, alkali compounds contribute to the active etching of silicon, and organic solvents contribute to the mask effect in etching and the selectivity between the (100) plane of the silicon substrate and the (110) plane of the silicon substrate. The surfactant contributes mainly to the formation of an appropriate shape of the texture, and the surfactant mainly contributes to the elimination of hydrogen bubbles generated by the etching reaction in a small state. It is thought that it contributes to the improvement of in-plane uniformity in formation.

In addition, when etching is performed using the etching solution composition according to the present invention to form a texture on the surface of the single crystal silicon substrate, the processing temperature is preferably 80 to 90 ° C. By doing so, it is possible to increase the efficiency of removing hydrogen generated during etching, that is, desorbing hydrogen from the surface of the silicon substrate that is the substrate to be processed. In addition, the etching processing time can be shortened.

In the above-described embodiment, the etching process is performed by immersing the silicon substrate. However, the silicon substrate may be in a stationary state or further oscillated when the silicon substrate is immersed. But you can. Further, the etching solution in which the silicon substrate is immersed may be stirred. Further, the present invention is not limited to this, and etching can be performed by other methods. Specifically, for example, a dipping process for bubbling with an inert gas may be used, or a spray process for supplying an etching solution to the surface of the silicon substrate by a spray nozzle may be used. Furthermore, the etching solution may be supplied in a state where the silicon substrate is transported in a flat flow.

It should be noted that the etching solution composition according to the present invention can appropriately form a texture with an addition amount of an organic solvent or a surfactant, that is, a content that is relatively at least. Therefore, the load on wastewater treatment can be reduced, which is advantageous in terms of environment and waste liquid treatment costs. Further, the odor can be reduced and the working environment can be greatly improved.

Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to these examples.

Tables 1 and 2 show the blending ratios and evaluation results of the etching solution compositions according to Examples 1 to 10 and Comparative Examples 1 to 6. Comparative Example 4 corresponds to the etching solution disclosed in Patent Document 1. Comparative Example 6 corresponds to the etching solution disclosed in Patent Document 5.

The abbreviations of the compounds shown in Table 1 are as follows. That is, Example 1 will be described as an example. In the etching solution composition, 3% by weight of sodium hydroxide as an alkali compound, 0.10% by weight of diethylene glycol monobutyl ether as an organic solvent, and amphoteric fluoride as a surfactant. Containing 100 ppm of polymerized polymer. In addition, as an etching liquid, a structure other than such an etching liquid composition is used as the remaining water.

(Alkali compounds)
NaOH: Sodium hydroxide KOH: Potassium hydroxide (organic solvent)
DGBE: Diethylene glycol monobutyl ether DMSO: Dimethyl sulfoxide FFA: Furfuryl alcohol 1,5-PD: 1,5-propanediol DGME: Diethylene glycol monomethyl ether IPA: Isopropyl alcohol (surfactant)
Material A: Amphoteric fluorinated polymer Material B: Sodium polyacrylate Material C: α-perfluorononenyloxy-ω-methylpolyethylene oxide Material D: Perfluoroalkylamine oxide Material E: Sodium salt of formalin condensate of naphthalenesulfonic acid ( Silicon compound)
Si: Metallic silicon SiO ₂ : Silicon dioxide

Here, the evaluation results were evaluated by the following method.

(Texture formation and evaluation method)
As the single crystal silicon substrate to be processed, a silicon substrate sliced by a fixed abrasive method and having a smooth surface by primary etching was used. And about formation of a texture, ie, an etching method, it performed by immersing the above-mentioned silicon substrate in the etching liquid which was 90 degreeC for 15 minutes. After immersion, the silicon substrate after etching was washed with water and dried, and the appearance was observed by visual observation and an electron microscope to confirm the surface state. Note that the same tendency is observed in Examples 1 to 10 even when a silicon substrate that is sliced by the free abrasive grain method and the surface is smoothed by primary etching and a silicon substrate that is not subjected to primary etching are used. It was seen.

(Etching rate measurement method and selection ratio calculation method)
The measurement of the etching rate is as follows. First, a Si (silicon) (100) substrate, a Si (110) substrate, and a Si (111) substrate in a mirror state were prepared. After removing the natural oxide film by Si from each prepared Si substrate by BHF, it was immersed in the etching liquid which concerns on an Example and a comparative example at 90 degreeC for 3 minutes, 5 minutes, and 10 minutes. After immersion, washing and drying were performed, and the etching amount was calculated from the weight change, surface area, and silicon density of the silicon substrate, and the etching rate was calculated and derived. Thus, the etching rate was measured. The unit of the etching rate, that is, the etching rate is μm / min (min.).

Furthermore, based on the result of the derived etching rate, the selection ratio which is the ratio of Si (100) and Si (110) and the selection ratio which is the ratio of Si (100) and Si (111) were calculated. In this way, the selection ratio was calculated. Describing Example 1, the selectivity (100) / (110) is Si (100) etching rate 1.63 ÷ Si (110) etching rate 0.46 = 3.54. Si (111) and the selection ratio (100) / (111) are described for reference.

(Judgment criteria for in-plane uniformity)
Judgment of in-plane uniformity was performed as follows. On the surface of the obtained silicon substrate after etching, the surface which is visually uniform and black is indicated by “◯” in Table 2 as having good in-plane uniformity. A sample with a partially clouded spot or a non-uniform black portion was visually marked with “Δ” in Table 2 as having poor in-plane uniformity. Those having few or no black portions by visual inspection are indicated by “x” marks in Table 2 as those having insufficient in-plane uniformity. In actual use, those marked with “O” can be applied.

(Judgment criteria for texture irregularities)
The criteria for determining the texture irregularities were as follows. On the surface of the obtained silicon substrate after etching, those with a uniform texture formed by observation with an electron microscope are indicated by “◯” in Table 2 as having good concavo-convex shape. In addition, the case where the texture is not partially formed by observation with an electron microscope or the case where the Si (100) surface is observed is marked with “Δ” in Table 2 as having an uneven texture. Indicated. In addition, by observation with an electron microscope, those with no texture formed are indicated by “x” marks in Table 2 assuming that the texture has an uneven shape. In actual use, those marked with “O” can be applied.

Referring to Table 1 and Table 2, for Examples 1 to 10, the texture shape is appropriate and the in-plane uniformity is good. This is apparent with reference to FIG. 3 and FIGS. FIG. 3 is a photograph showing the appearance of the single crystal silicon according to Example 1. FIG. 6 is an electron micrograph showing an enlarged surface of the single crystal silicon according to Example 1, and shows a case where the magnification is 1000 times. FIG. 7 is an electron micrograph showing an enlarged surface of the single crystal silicon according to Example 1, and shows a case where the magnification is 2000 times. FIG. 8 is an electron micrograph showing an enlarged surface of single crystal silicon according to Example 2, and shows a case where the magnification is 1000 times. FIG. 9 is an electron micrograph showing an enlarged surface of single crystal silicon according to Example 2, and shows a case where the magnification is 2000 times. Here, in each of Examples 1 to 10, the value of the selection ratio (100) / (110) is larger than 3 and 3 or more.

That is, the etching method according to the present invention is an etching method in which the surface of a single crystal silicon substrate is etched to form an uneven shape, and the etching rate of the (100) plane of the silicon substrate and the (110) plane of the silicon substrate Etching is performed with a selection ratio, which is a ratio to the etching rate, of 3 or more.

On the other hand, in Comparative Examples 1 to 6, the shape of the texture is insufficient, and the in-plane uniformity is inferior. This is apparent with reference to FIGS. 4, 5, and 10-13. FIG. 4 is a photograph showing the appearance of single crystal silicon according to Comparative Example 5. FIG. 5 is a photograph showing the appearance of single crystal silicon according to Comparative Example 6. FIG. 10 is an electron micrograph showing an enlarged surface of single crystal silicon according to Comparative Example 5, and shows a case where the magnification is 1000 times. FIG. 11 is an electron micrograph showing an enlarged surface of single crystal silicon according to Comparative Example 5, and shows a case where the magnification is 2000 times. FIG. 12 is an electron micrograph showing an enlarged surface of single crystal silicon according to Comparative Example 6, and shows a case where the magnification is 1000 times. FIG. 13 is an electron micrograph showing an enlarged surface of single crystal silicon according to Comparative Example 6, and shows a case where the magnification is 2000 times. Here, in each of Comparative Examples 1 to 6, the value of the selection ratio (100) / (110) is 3 or less. Moreover, in FIG. 4, it can be grasped that the texture is partially formed and unevenness in the texture formation occurs on the surface. In FIG. 5, the texture is hardly formed, the texture is not sufficiently formed, and there is almost no black portion. Moreover, in FIG. 5, it can be grasped that there is gloss due to the smoothness of the original surface.

The embodiment of the present invention has been described above with reference to the drawings, but the present invention is not limited to the illustrated embodiment. Various modifications and variations can be made to the illustrated embodiment within the same range or equivalent range as the present invention.

The etching solution composition and the etching method according to the present invention are effectively used when a silicon substrate having a high light confinement effect is manufactured in a single crystal silicon substrate.

11, 13 Silicon substrate, 12 surface, 14, 15 tilt.

Claims

An etching solution composition that forms an uneven shape by etching the surface of a single crystal silicon substrate,
An etchant composition comprising an alkali compound, an organic solvent, and a surfactant.
2. The etching solution composition according to claim 1, wherein the organic solvent includes at least one selected from the group consisting of glycol ethers, alcohols, nitrogen-containing organic solvents, and sulfur-containing organic solvents.
The organic solvent is ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monobenzyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, furfuryl alcohol, tetrahydro The etching solution composition according to claim 1, comprising at least one selected from the group consisting of furfuryl alcohol, N-methyl-2-pyrrolidone, dimethyl sulfoxide, and sulfolane.
The surfactant includes at least one selected from the group consisting of a fluorine-based anionic surfactant, a fluorine-based nonionic surfactant, a fluorine-based amphoteric surfactant, and a hydrocarbon-based anionic surfactant. The etching liquid composition according to claim 1.
2. The etching solution composition according to claim 1, wherein the alkali compound includes at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, and tetramethylammonium hydroxide.
The etching solution composition according to claim 1, comprising silicon or a silicon compound.
An etching method for forming a concavo-convex shape by etching a surface of a single crystal silicon substrate,
An etching method in which etching is performed using an etchant composition containing an alkali compound, an organic solvent, and a surfactant.
An etching method for forming a concavo-convex shape by etching a surface of a single crystal silicon substrate,
An etching method in which etching is performed with a selection ratio which is a ratio of an etching rate of the (100) plane of the silicon substrate to an etching rate of the (110) plane of the silicon substrate being 3 or more.
The etching method according to claim 7, wherein the single crystal silicon substrate is immersed in the etching solution composition and etching is performed by wet etching.
The single crystal silicon substrate includes at least one of a group consisting of a substrate sliced by a fixed abrasive method, a substrate sliced by a free abrasive method, and a substrate whose surface is subjected to a primary etching process. Item 8. The etching method according to Item 7.