Reactive-Ion Etching of Smooth Vertical Walls in Silicon

An advanced technique of deep reactive-ion etching (DRIE) has been developed for fabricating smooth vertical walls in silicon wafers. These walls are suitable for use as bounding surfaces of optical waveguides in photonic and optoelectronic devices. The roughness of a typical 8-µm-high vertical wall surface of a waveguide made by this technique is <20 nm; by keeping the roughness at such a low level, one helps to ensure that the waveguide is capable of low-loss optical transmission.