2.4 Dielectrics Wet Etch. Etch rates, in aqueous solutions, for dielectrics layers such as SiO 2, Si x N y, Si x O y N z, and Al 2 O 3 are strictly bound to dielectrics layer chemical and physical properties, conveyed by their deposition methods. It has been widely verified, for example, that thermal oxide, due to its higher density, etches more …Web