Maskless, fast and highly selective etching of fused silica with gaseous fluorine and gaseous hydrogen fluoride

is tied to the development of integrated electronic circuit technology [6].The silicon slab needs to be covered with glass in order to obtain a working microfluidic device.In this procedure, glass is relegated as a top seal for silicon chips.This is due to the fact that, as opposed to silicon, the etching of glass is isotropic; therefore, the SiO 2 lab-onchip devices are fabricated by means of photolithography only with planar geometries.However, when compared to silicon, glass has a lower cost, good transparency and good corrosion resistance.Thus, it remains a good candidate for being used as a main substrate in microfluidic devices, assuming that a better control of the aspect ratio of the etched channels is possible.To overcome the glass isotropic etching limitations, standard photolithographic techniques have been employed and photo-sensitive glasses have also been developed [2].The possibility of locally modifying the glass structure