Microfabrication of SiN membrane nanosieve using anisotropic reactive ion etching (ARIE) with an Ar/CF4 gas flow

We have designed, fabricated, and characterized a low-stressed silicon nitride (SiN) membrane nanosieve (100 microm x 100 microm) using an anisotropic reactive ion etching (ARIE) combining with gas mixture, thus maintaining compatibility with the complementary metal-oxide semiconductor integrated circuit (CMOS IC) processes. The holes pattern of this nanosieve membrane was precisely controlled under 30 nm diameter by the electron beam writing. By employing mainly anisotropic reactive ion etching plus diffusion to the depth direction, the etch holes size was controlled to be the same with patterns on the e-beam resist (ER). This nanosieve membrane has proper mechanical strength withstanding up to one bar of transmembrane pressure. And it can endure harsh treatments such as high temperature up to 800 degrees C. In addition, it is inert to a number of strong chemicals including the piranha (H2SO4 + H2O2) solution, highly-concentrated potassium hydroxide (KOH), hydrogen fluoride (HF), hydrogen chloride (HCI), and nitric acid (HNO3).