Etching Silicon Nitride Using Dilute Hydrofluoric Acid

A method for processing semiconductor substrates, the method comprising:

• providing a semiconductor substrate comprising a first structure, a second structure, and a third structure,
• the first structure comprising a photoresist pattern,
• the second structure comprising silicon nitride and having a thickness of between 20 Angstroms and 1000 Angstroms, and
• the third structure comprising silicon oxide and being covered by the second structure;
• exposing the semiconductor substrate to an etching solution comprising hydrofluoric acid, a non-fluorinated acid, water, and one or more polar solvents selected from the group consisting of ethylene glycol (EG), propylene carbonate (PC), dichloromethane (DCM), tetrahydrofuran (THF), ethyl acetate, acetone, dimethylformamide (DMF), acetonitrile (MeCN), dimethyl sulfoxide (DMSO), propylene carbonate, formic acid, n-butanol, isopropanol (IPA), n-propanol, ethanol, and methanol,
• wherein a volumetric ratio of water to hydrofluoric acid is between 1000:1 and 10,000:1, and
• wherein the etching solution is kept at a temperature of between 60° C. and 90° C.;
• and
• etching the second structure,
• wherein the thickness of the first structure is reduced by less than 200 Angstroms.