Patent ID: 8540891

Claim:
A process for the selective etching of patterns or lines on silicon surfaces and layers to a depth of 1-3 μm, said process comprising: applying a printable thickened, alkaline liquid etching medium (a) over the entire surface area of said surface or layer, or (b) in accordance with an etch structure mask specifically only to the areas of the surface where etching is desired, and removing said medium after an exposure time of from 30 s to 5 minutes, wherein said etching medium is effective at temperatures from 70 to 150° C. or can be activated by the input of energy, and wherein said etching medium comprises (a) 30-40% by weight of a potassium hydroxide etching component, based on the total amount of an etching medium, (b) from 55-75% by weight, based on the total amount of said etching medium, of a solvent which is a mixture of water and at least one other solvent that is diethylene glycol, dipropylene glycol, polyethylene glycols, 1,2-propanediol, 1,4-butanediol, 1,3-butanediol, glycerol, 1,5 pentanediol, 2-ethyl-1-hexanol, acetophenone, methyl-2-hexanone, 2-octanone, 4-hydroxy-4-methyl-2-pentanone, 1-methyl-2-pyrrolidone, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether, triethylene glycol monomethyl ether, diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, or a carboxylic acid ester, (c) 1.0-10% by weight of a thickener which is hydroxyalkylguar, xanthan gum, and/or ethyl hydroxypropyl or hydroxyethylcellulose, sodium carboxymethylhydroxyethylcellulose, homopolymers or copolymers based on functionalised vinyl units of acrylic acid, acrylates or alkyl methacrylates (C 10 -C 30 ), individually or in a mixture, and (d) optionally an additive that is a thixotropic agent, a flow-control agent, a deaerator or an adhesion promoter, and wherein said etching medium selectively etches patterns or lines on said silicon surface or layer to a depth of 1-3 μm.