Provided are methods for processing semiconductor substrates. The methods involve etching silicon nitride structures using phosphoric acid solutions maintained at low temperatures, such as between about 110° C. and 130° C. These temperatures provide adequate etching rates and do not damage surrounding metal silicide and silicon oxide structures. The etching rates of silicon nitride may be 10 Angstroms per minute and greater. Lower temperatures also allow decreasing concentrations of phosphoric acid in the etching solutions, which in some embodiments may be less than 90 weight percent. As a result, more selective etching of the silicon nitride structures may be achieved. This selectivity may be as high as hundred times relative to the silicide and silicon oxide structures. The surface conductivity of the silicide structures may remain substantially unchanged by this etching process.