Highly Selective Si3N4/SiO2 Etching for 3D NAND Manufacturing with H3PO4- Free Etchant

Si 3 N 4 film could be selectively removed by novel H 3 PO 4 -free etchant (PFE). Instead of H 3 PO 4 , another type of nucleophile is needed for selective etching of Si 3 N 4 . In order to increase Si 3 N 4 etching rate and Si 3 N 4 /SiO 2 etch selectivity, additives were optimized in the H 3 PO 4 -free etchant. Much faster etch rate of Si 3 N 4 with no oxide regrowth was achievable in the high number Si 3 N 4 /SiO 2 layer by using this etchant.