Silica (SiO 2 ), comprises tetragonal SiO 4 units and each of them is connected to the neighboring units by covalent siloxane bonds. Thus, each oxygen is shared between two tetrahedra creating a covalent interconnected three-dimensional silicate network. Chemical etching, with HF, breaks these bridging oxygen bonds and releases silicon from the surface. When HF dissolves in water, the solution contains H + , F -, and HF - 2 ions along with undissociated molecules. Various etching mechanisms have been reported based on the adsorption of these fluorine species. As the adsorption of above mentioned ionic species increases the electron density on the bridging oxygen, this oxygen becomes more basic which leads to the adsorption of more H + ions and results in the breakage of more siloxane bonds per unit time. In a different approach, the bridging oxygen reacts with H 2 O or H + and results in the formation of silanol groups and Si-F species. Some of the reports on etching kinetics addressed that the protonation or deprotonation of the neutral hydroxylated surface groups at SiO 2 /water interface led to the adsorption of fluoride ions as Si-F complex species and its subsequent detachment resulted in the dissolution step. In general, the etching process comprises two elementary chemical reactions at the SiO 2 surface as follows, (a) attack of acidic components on siloxane bonds and the formation of silanol species and (b) the reaction of fluorinated species on the surface to form Si-F complexes and its removal from the surface to the etchant solution. These fluoride species/ions penetrate the silica surface and form pit-like surface structures. Typically, the etching process is considered a heterogeneous reaction and it can be depicted as follows: HF reacts with SiO 2 and forms H 2 SiF 6 and water. The overall chemical reactions for HF etching of silica are given as follows. SiO