Described are compositions and methods useful for wet-etching a microelectronic device substrate that includes silicon nitride; the compositions including phosphoric acid, hexafluorosilicic acid, and an amino alkoxy silane, and optionally one or more additional optional ingredients; a wet etching method of a substrate that includes silicon nitride and silicon oxide, that uses a composition as described, can achieve useful or improved silicon nitride etch rate, useful or improved silicon nitride selectivity, a combination of these, and optionally a reduction in particles present at a substrate surface after etching.