Printable etching media for silicon dioxide and silicon nitride layers

Abstract

The present invention relates to a novel printable etching medium having non-Newtonian flow behaviour for the etching of surfaces in the production of solar cells, and to the use thereof. The present invention furthermore also relates to etching and doping media which are suitable both for the etching of inorganic layers and also for the doping of underlying layers. In particular, they are corresponding particle-containing compositions by means of which extremely fine structures can be etched very selectively without damaging or attacking adjacent areas.

1 .- 30 . (canceled) 
     
     
         31 . A composition for the etching and optionally doping of a silicon oxide, silicon nitride or glass layer comprising:
 at least one etching component comprising: one or more forms of phosphoric acid, a phosphoric acid salt or a compound which decomposes to the corresponding phosphoric acid, or at least one of hydrochloric acid, sulfuric acid or nitric acid;   optionally, at least one organic acid selected from the group of alkylcarboxylic acids, hydroxycarboxylic acids and dicarboxylic acids;   at least one solvent;   a finely particulate inorganic powder of graphite and/or carbon black having a relative particle diameter of less than 5 μm;   a finely particulate organic powder in the form of a finely particulate plastic powder having a relative particle diameter in the range from 10 nm to 50 μm selected from the group of polystyrenes, polyacrylates, polyamides, polyimides, polymethacrylates, melamine resin, urethane resin, benzoguanine resin, phenolic resin, silicone resins, micronised cellulose, fluorinated polymers (PTFE, PVDF) and micronised waxes;   optionally, a finely particulate inorganic powder selected from the group of aluminum oxide, calcium fluoride, boron oxide, and sodium chloride;   at least one fluxing agent additive;   optionally a homogeneously dissolved organic thickener; and   optionally, one or more antifoam, thixotropic agent, flow-control agent, deaerator or adhesion promoter additives;   
       in the form of a printable paste. 
     
     
         32 . The composition of  claim 31 , wherein said printable composition in the form of a paste comprises said finely particulate plastic powder have a relative particle diameter in the range from 10 nm to 50 μm. 
     
     
         33 . The composition of  claim 31 , wherein said printable composition in the form of a paste comprises said finely particulate plastic powder have a relative particle diameter in the range from 100 nm to 30 μm. 
     
     
         34 . The composition of  claim 31 , wherein said printable composition in the form of a paste comprises said finely particulate plastic powder have a relative particle diameter in the range from 1 μm to 10 μm. 
     
     
         35 . The composition of  claim 31 , wherein the composition comprises the inorganic and organic powders in an amount of 1 to 80% by weight, based on the total amount of the composition. 
     
     
         36 . The composition of  claim 31 , wherein the composition comprises the inorganic and organic powders in an amount of 10 to 50% by weight, based on the total amount of the composition. 
     
     
         37 . The composition of  claim 31 , wherein the composition comprises the inorganic and organic powders in an amount of 20 to 40% by weight, based on the total amount of the composition. 
     
     
         38 . The composition of  claim 31 , wherein the composition comprises the at least one etching component in an amount of 12 to 30% by weight, based on the total amount of the composition. 
     
     
         39 . The composition of  claim 31 , wherein the composition comprises the at least one etching component in an amount of 2 to 20% by weight, based on the total amount of the composition. 
     
     
         40 . The composition of  claim 31 , wherein the composition comprises the at least one etching component in an amount of 5 to 15% by weight, based on the total amount of the composition. 
     
     
         41 . The composition of  claim 31 , wherein the composition comprises thickeners in an amount of 3 to 20% by weight, based on the total amount of the composition. 
     
     
         42 . The composition of  claim 31 , wherein the composition further comprises an organic acid selected from the group consisting of formic acid, acetic acid, lactic acid and oxalic acid. 
     
     
         43 . The composition of  claim 31 , wherein the acids are in a concentration range from 0 to 80% by weight, based on the total amount of the composition, where the acids each have a pKa value of between 0 and 5. 
     
     
         44 . The composition of  claim 31 , wherein the solvent comprises: water, mono- or polyhydric alcohols or ethers thereof, esters, esters of carbonic acid, ketones, or mixtures thereof, in an amount of 10 to 90% by weight, based on the total amount of the composition. 
     
     
         45 . The composition of  claim 44 , wherein the solvent comprises water, glycerol, 1,2-propanediol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 2-ethyl-1-hexenol, ethylene glycol, diethylene glycol, dipropylene glycol, ethylene glycol monobutyl ether, triethylene glycol monomethyl ether, diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, [2,2-butoxy(ethoxy)]ethyl acetate, propylene carbonate, acetophenone, methyl-2-hexanone, 2-octanone, 4-hydroxy-4-methyl-2-pentanone, 1-methyl-2-pyrrolidone or mixtures thereof. 
     
     
         46 . The composition of  claim 31 , wherein the composition comprises one or more homogeneously dissolved thickeners selected from the group consisting of: cellulose and cellulose derivatives, starch and starch derivatives, polyvinylpyrrolidone, and polymers based on acrylates or functionalised vinyl units, in an amount of 0.5 to 25% by weight, based on the total amount of the composition. 
     
     
         47 . The composition of  claim 31 , wherein the composition comprises 0 to 5% by weight, based on the total amount of the composition, of additives selected from antifoams, thixotropic agents, flow-control agents, deaerators, and adhesion promoters. 
     
     
         48 . The composition of  claim 31 , wherein the composition has a viscosity at 20° C. in the range from 6 to 35 Pa·s at a shear rate of 25 s −1 . 
     
     
         49 . The composition of  claim 31 , wherein the composition has a viscosity at 20° C. in the range from 10 to 25 Pa·s at a shear rate of 25 s −1 . 
     
     
         50 . The composition of  claim 31 , wherein the composition has a viscosity at 20° C. in the range from 15 to 20 Pa·s at a shear rate of 25 s −1 . 
     
     
         51 . The composition of  claim 31 , wherein the composition comprises fluxing agent additives selected from the group consisting of dimethylammonium chloride, diammonium hydrogenphosphate, diethylamine phosphate, urea, magnesium stearate, sodium acetate, triethanolamine hydrochloride and oxalic acid dihydrate, individually or in the form of a mixture, in an amount of 0.05 to 25% by weight, based on the total amount of the composition.