Selective wet etching of Si3N4/SiO2 in phosphoric acid with the addition of fluoride and silicic compounds ?
Selective wet etching of Si3N4 to SiO2 in H3PO4. Both etch rate and selectivity strongly related to the amount of fluorine added in H3PO4. Etch selectivity modulated by addition of fluoride and silicic compounds to H3PO4. Etch selectivity greater than 104 with addition of Si(OH)4 in the presence of NH4F and NH4HF2.
selectivity selective etching reaction mechanism silicon nitride