Wet etching of silicon nitride with heated phosphoric acid
Wet Etching of Silicon Nitride with Heated Phosphoric Acid The boiling point of phosphoric acid varies with the concentration of the acid. On the graph below, the x-axis shows the boiling point (140ºC – 200ºC) of phosphoric acid solutions for a range of acid concentration (79.5% – 94.5%). The etch rate of silicon nitride varies with the temperature and the concentration of the acid.