Etching fluid for forming texture and texture-forming method using same

Abstract

Provided are: an etching fluid for forming texture on a silicon substrate, applicable to both silicon substrates manufactured using a loose-abrasive grain method and silicon substrates manufactured using a fixed-abrasive grain method, which can stably form a good texture uniformly on the substrate surface, and does not have volatility of additive components in the normal usage temperature range of 60-95°C; and an etching method. An etching fluid is used that contains an alkali component (A), a phosphonic acid derivative (B) or salt thereof, and a compound (C) having at least one type of group selected from a group comprising a carboxyl group, a sulfo group, groups thereof forming a salt, and a carboxymethyl group.

Description

technical field [0001] The present invention relates to an etching solution and an etching method for forming a textured uneven structure on the surface of a silicon substrate. Background technique [0002] A crystalline silicon substrate used for a solar cell is generally treated with a surface structure treatment called texture in order to reduce the reflectance of light on the substrate surface and efficiently absorb light. [0003] At present, a single crystal silicon substrate is usually etched by immersing it in an alkaline solution such as sodium hydroxide or potassium hydroxide to form a textured structure such as a pyramid. Other additives can form a textured structure of uniform size or shape. [0004] As an etchant for forming such a texture, for example, a solution obtained by mixing an aqueous solution of sodium hydroxide or potassium hydroxide with isopropyl alcohol (IPA) is generally used. The texture can be formed by immersing the silicon substrate for 10-3...

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Problems solved by technology

[0006] In order to meet the various requirements mentioned above, various methods other than IPA have been proposed as components of the etchant for texture formation, but the current situation is that it is not yet possible to comprehensively satisfy quality control such as excellent texture formation and concentration control at the time of use. Etching solution or additives that are also easy to etch (Patent Documents 1 to 6)

[0007] In addition, in recent years,

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